Note: Descriptions are shown in the official language in which they were submitted.
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METAL UTILIZATION
IN SUPPORTED, METAL-CONTAINING CATALYSTS
FIELD OF THE INVENTION
[0001] Generally, the present invention relates to
improvements in metal utilization in supported, metal-containing
catalysts. For example, the present invention relates to methods
for directing and/or controlling metal deposition onto surfaces of
porous substrates. More particularly, some embodiments of the
present invention relate to methods for treating porous substrates
(e.g., porous carbon substrates or porous metal substrates) to
provide treated substrates having one or more desirable properties
(e.g., a reduced surface area attributable to pores having a
nominal diameter within a predefined range) that may be utilized
as supports for metal-containing catalysts.
[0002] The present invention also relates to methods for
preparing catalysts in which a first metal is deposited onto a
support (e.g., a porous carbon support) to provide one or more
regions of a first metal at the surface of the support, and a
second metal is deposited at the surface of the one or more
regions of the first metal. Generally, the electropositivity of
the first metal (e.g., copper or iron) is greater than the
electropositivity of the second metal (e.g., a noble metal such as
platinum) and the second metal is deposited at the surface of the
one or more regions of the first metal by displacement of the
first metal.
[0003] The present invention further relates to treated
substrates, catalyst precursor structures and catalysts prepared
by these methods.
[0004] The invention further relates to use of catalysts
prepared as detailed herein in catalytic oxidation reactions, such
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as oxidation of a substrate selected from the group consisting of
N-(phosphonomethyl)iminodiacetic acid or a salt thereof,
formaldehyde, and/or formic acid.
BACKGROUND OF THE INVENTION
[0005] N-(phosphonomethyl)glycine (known in the agricultural
chemical industry as glyphosate) is described in Franz, U.S.
Patent No. 3,799,758. Glyphosate and its salts are conveniently
applied as a post-emergent herbicide in aqueous formulations. It
is a highly effective and commercially important broad-spectrum
herbicide useful in killing or controlling the growth of a wide
variety of plants, including germinating seeds, emerging
seedlings, maturing and established woody and herbaceous
vegetation, and aquatic plants.
[0006] Various methods for producing glyphosate are known in
the art, including various methods utilizing carbon-supported
noble metal-containing catalysts. See, for example, U.S. Patent
No. 6,417,133 to Ebner et al. and Wan et al. International
Publication No. WO 2006/031938. Generally, these methods include
the liquid phase oxidative cleavage of N-
(phosphonomethyl)iminodiacetic acid (i.e., PMIDA) in the presence
of a carbon-supported noble metal-containing catalyst. Along with
glyphosate product, various by-products may form, such as
formaldehyde, formic acid (which is formed by the oxidation of the
formaldehyde by-product); aminomethylphosphonic acid (AMPA) and
methyl aminomethylphosphonic acid (MAMPA), which are formed by the
oxidation of N-(phosphonomethyl)glycine; and iminodiacetic acid
(IDA), which is formed by the de-phosphonomethylation of PMIDA.
These by-products may reduce glyphosate yield (e.g., AMPA and/or
MAMPA) and may introduce toxicity issues (e.g., formaldehyde).
Thus, significant by-product formation is preferably avoided.
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[0007] It is generally known in the art including, for
example, as described in Ebner et al. U.S. 6,417,133 and by Wan et
al. in International Publication No. WO 2006/031938, that carbon
primarily catalyzes the oxidation of PMIDA to glyphosate and the
noble metal primarily catalyzes the oxidation of by-product
formaldehyde to carbon dioxide, and water. The catalysts of Ebner
et al. U.S. 6,417,133 and Wan et al.
WO 2006/031938 have proven to be highly advantageous and effective
catalysts for the oxidation of PMIDA to glyphosate and the
oxidation of by-products formaldehyde and formic acid to carbon
dioxide and water without excessive leaching of noble metal from
the carbon support. These catalysts are also effective in the
operation of a continuous process for the production of glyphosate
by oxidation of PMIDA. Even though these catalysts are effective
in PMIDA oxidation and are generally resistant to noble metal
leaching under PMIDA oxidation conditions, there exist
opportunities for improvement.
[0008] For example, the distribution and/or size of the pores
of the porous substrates utilized in noble metal-containing
catalysts may impact catalyst performance and metal utilization.
Methods to introduce compounds (i.e., pore blocking compounds)
within pores of substrates to modify metal deposition are known in
the art. See, for example, U.S. Patent No. 5,439,859 to Durante
et al.
[0009] One object of the present invention is development of
catalysts effective for the oxidation of PMIDA, formaldehyde,
and/or formic acid that more efficiently utilize the costly noble
metal, and methods for their preparation. More efficient metal
usage may provide catalysts more active than conventional
catalysts. Another object of the present invention is development
of methods for preparing effective catalysts that require a
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reduced proportion of costly noble metal as compared to
conventional catalysts, while still exhibiting suitable activity.
SUMMARY OF THE INVENTION
[0010] This invention provides catalysts and methods for
preparing catalysts that are useful in heterogeneous oxidation
reactions, including the preparation of glyphosate by the
oxidation of PMIDA.
[0011] Briefly, therefore, the present invention is directed
to oxidation catalysts comprising a particulate carbon support, a
first metal, and a second metal, the support having at its surface
particles comprising the first metal and the second metal.
[0012] In at least one embodiment, the second metal
distribution within at least one of the particles as characterized
by energy dispersive x-ray (EDX) line scan analysis as described
in Protocol B produces a second metal signal that varies by no
more than about 25% across a scanning region having a dimension
that is at least about 70% of the largest dimension of the at
least one particle. In a further embodiment, the second metal
distribution within at least one of the particles as characterized
by EDX line scan analysis as described in Protocol B produces a
second metal signal that varies by no more than about 20% across a
scanning region having a dimension that is at least about 60% of
the largest dimension of the at least one particle. In another
embodiment, the second metal distribution within at least one of
the particles as characterized by EDX line scan analysis as
described in Protocol B produces a second metal signal that varies
by no more than about 15% across a scanning region having a
dimension that is at least about 50% of the largest dimension of
the at least one particle.
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[0013] The present invention is also directed to an oxidation
catalyst comprising a particulate carbon support, copper, and
platinum, the support having at its surface particles comprising
copper and platinum. The platinum distribution within at least
70% (number basis) of the particles as characterized by EDX line
scan analysis as described in Protocol B produces a platinum
signal that varies by no more than about 25% across a scanning
region having a dimension that is at least about 70% of the
largest dimension of said particles.
[0014] The present invention is further directed to an
oxidation catalyst comprising a particulate carbon support, a
first metal, and a noble metal, the support having at its surface
metal particles comprising the first metal and the noble metal.
The catalyst is characterized as chemisorbing at least 975 moles
CO per gram of catalyst per gram noble metal during Cycle 2 of
static carbon monoxide chemisorption analysis as described in
Protocol A.
[0015] The present invention is also directed to an oxidation
catalyst comprising a particulate carbon support, a first metal,
and a noble metal, the support having at its surface metal
particles comprising the first metal and the noble metal, wherein
the metal particles comprise a core comprising the first metal and
a shell at least partially surrounding the core and comprising the
noble metal, wherein at least about 70% of the noble metal is
present within the particle shell.
[0016] In a further embodiment, the present invention is
directed to an oxidation catalyst comprising a particulate carbon
support, platinum, and copper, the support having at its surface
metal particles comprising platinum and copper, wherein the atom
percent of platinum at the surface of the particles is at least
about 10%.
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[0017] In a still further embodiment, the present invention
is directed to an oxidation catalyst comprising a particulate
carbon support, a first metal, and a noble metal, the support
having at its surface metal particles comprising the first metal
and the noble metal, wherein the metal particles comprise a core
comprising the first metal and a shell at least partially
surrounding the core and comprising the noble metal; and the
catalyst is characterized as chemisorbing at least 975 moles CO
per gram of catalyst per gram noble metal during Cycle 2 of static
carbon monoxide chemisorption analysis as described in Protocol A.
[0018] In another embodiment, the present invention is
directed to an oxidation catalyst comprising a particulate carbon
support, platinum, and copper, the support having at its surface
metal particles comprising platinum and copper, wherein the atom
percent of platinum at the surface of the particles is at least
about 5%; and the catalyst is characterized as chemisorbing at
least 500 moles CO per gram of catalyst per gram noble metal
during Cycle 2 of static carbon monoxide chemisorption analysis as
described in Protocol A.
[0019] In a still further embodiment, the present invention
is directed to an oxidation catalyst comprising a particulate
carbon support, a first metal, and a noble metal, the support
having at its surface metal particles comprising the first metal
and the noble metal, wherein the metal particles comprise a core
comprising the first metal and a shell at least partially
surrounding the core and comprising the noble metal; the noble
metal constitutes less than 5% by weight of the catalyst; and the
catalyst is characterized as chemisorbing at least about 800 moles
CO per gram of catalyst per gram noble metal during Cycle 2 of
static carbon monoxide chemisorption analysis as described in
Protocol A.
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[0020] The present invention is also directed to an oxidation
catalyst comprising a particulate carbon support having metal
particles at a surface thereof comprising a first metal and a
second metal, wherein the electropositivity of the first metal is
greater than the electropositivity of the second metal and the
second metal is deposited by displacement of first metal ions of
one or more regions of first metal of a catalyst precursor
structure; and the weight ratio of the second metal to the first
metal is at least about 0.25:1.
[0021] The present invention is also directed to processes
for oxidizing a substrate selected from the group consisting of N-
(phosphonomethyl)iminodiacetic acid or a salt thereof,
formaldehyde, and formic acid. Generally, the process comprises
contacting the substrate with an oxidizing agent in the presence
of an oxidation catalyst prepared by the methods detailed herein
and/or as described herein. For example, in one embodiment the
catalyst comprises a first metal, a noble metal, and a porous
carbon support, the catalyst comprising one or more first metal
regions at the surface of the carbon support and one or more noble
metal regions at the surface of the one or more first metal
regions, wherein the first metal has an electropositivity greater
than the electropositivity of the noble metal.
[0022] The present invention is further directed to various
methods for preparing a catalyst comprising a first metal, a
second metal, and a porous support having a surface comprising
pores of a nominal diameter within a predefined range and pores of
a nominal diameter outside the predefined range.
[0023] In one embodiment, the method comprises disposing a
pore blocking agent within pores of the porous support having a
nominal diameter within the predefined range, the pore blocking
agent having at least one dimension relative to the openings of
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the pores having a nominal diameter within the predefined range
such that the pore blocking agent is preferentially retained
within the pores; contacting the support with a first metal
deposition bath comprising an aqueous medium and ions of the first
metal, thereby depositing the first metal at the surface of the
porous support within the pores having a nominal diameter outside
the predefined range to form a catalyst precursor structure having
one or more regions of the deposited first metal at the surface of
the support among the pores of a nominal diameter outside the
predefined range; and contacting the catalyst precursor structure
with a second metal deposition bath comprising ions of the second
metal, thereby depositing the second metal at the surface of the
catalyst precursor structure.
[0024] In another embodiment, the method comprises contacting
the support and a first metal deposition bath comprising an
aqueous medium, ions of the first metal, and a coordinating agent
that forms a coordination compound with the first metal having at
least one dimension larger than the nominal diameter of the pores
within the predefined range, thereby depositing the first metal at
the surface of the support within the pores having a nominal
diameter outside the predefined range to form a catalyst precursor
structure having one or more regions of the deposited first metal
at the surface of the support; and contacting the catalyst
precursor structure with a second metal deposition bath comprising
ions of the second metal, thereby depositing the second metal at
the surface of the catalyst precursor structure.
[0025] The present invention is also directed to methods for
preparing catalysts comprising a first metal, a second metal, and
a porous carbon support.
[0026] In one embodiment, the method comprises contacting the
porous carbon support with a first metal deposition bath
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comprising ions of the first metal, thereby depositing the first
metal at the surface of the porous carbon support to form a
catalyst precursor structure having one or more regions of the
deposited first metal at the surface of the support, wherein the
first metal has an electropositivity greater than the
electropositivity of the second metal; contacting the catalyst
precursor structure with a second metal deposition bath comprising
ions of the second metal, thereby depositing the second metal at
the surface of the catalyst precursor structure by displacement of
the first metal from one or more of the regions; and heating the
catalyst precursor structure having the first and second metals
deposited at the surface of the catalyst precursor structure to a
temperature of at least about 500 C in a non-oxidizing environment.
[0027] In a further embodiment, the method comprises
contacting the porous carbon support with a first metal deposition
bath comprising ions of the first metal, thereby depositing the
first metal at the surface of the porous carbon support to form a
catalyst precursor structure having one or more regions of the
deposited first metal at the surface of the support, wherein the
carbon support has a Langmuir surface area of at least about
500 m2/g and the first metal has an electropositivity greater than
the electropositivity of the second metal; and contacting the
catalyst precursor structure with a second metal deposition bath
comprising ions of the second metal, thereby depositing the second
metal at the surface of the catalyst precursor structure by
displacement of the first metal from one or more of the regions.
[0028] The present invention is also directed to methods for
preparing a catalyst comprising a first metal, a noble metal, and
a porous support. In one embodiment, the method comprises
contacting the support and a first metal deposition bath
comprising an aqueous medium, ions of the first metal and a
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coordinating agent that forms a coordination compound with the
first metal, thereby depositing the first metal at the surface of
the support to form a catalyst precursor structure having one or
more regions of the deposited first metal at the surface of the
support, wherein the first metal has an electropositivity greater
than the electropositivity of the noble metal; and contacting the
catalyst precursor structure with a noble metal deposition bath
comprising ions of the noble metal, thereby depositing the noble
metal at the surface of the catalyst precursor structure by
displacement of the first metal from one or more of the regions.
[0029] In a further embodiment, the method comprises
contacting the support with a first metal deposition bath
comprising an aqueous medium and ions of the first metal, thereby
depositing first metal at the surface of the support to form a
catalyst precursor structure having one or more regions of the
deposited first metal at the surface of the support, wherein the
first metal has an electropositivity greater than the
electropositivity of the noble metal; and contacting the catalyst
precursor structure with a noble metal deposition bath comprising
ions of the noble metal, thereby depositing the noble metal at the
surface of the catalyst precursor structure by displacement of the
first metal from one or more of the regions, wherein substantially
all the noble metal is deposited by the displacement, or the
noble metal ions consist essentially of noble metal ions having an
oxidation number of 2.
[0030] In another embodiment, the method comprises contacting
the support with a first metal deposition bath comprising an
aqueous medium, ions of the first metal, and a pore blocking
agent, thereby disposing the pore blocking agent within pores of
the substrate having a nominal diameter within a predefined range,
wherein the pore blocking agent has at least one dimension
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relative to the opening of the pores of the predefined range
sufficient such that the pore blocking agent is preferentially
retained within the pores, and depositing first metal at the
surface of the support within pores having a nominal diameter
outside the predefined range, thereby forming a catalyst precursor
structure having one or more regions of the deposited first metal
at the surface of the support, wherein the first metal has an
electropositivity greater than the electropositivity of the noble
metal; and contacting the catalyst precursor structure with a
noble metal deposition bath comprising ions of the noble metal,
thereby depositing the noble metal at the surface of the catalyst
precursor structure by displacement of the first metal from one or
more of regions.
[0031] The present invention is also directed to methods for
preparing a catalyst comprising a first metal, a noble metal, and
a porous support having a surface comprising pores of a nominal
diameter within a predefined range and pores of a nominal diameter
outside the predefined range. In one embodiment, the method
comprises contacting the support and a first metal deposition bath
comprising an aqueous medium, ions of the first metal and a
coordinating agent that forms a coordination compound with the
first metal having at least one dimension larger than the nominal
diameter of the pores within the predefined range, thereby
depositing the first metal at the surface of the support within
the pores having a nominal diameter outside the predefined range
to form a catalyst precursor structure having one or more regions
of the deposited first metal at the surface of the support; and
contacting the catalyst precursor structure with a noble metal
deposition bath comprising ions of the noble metal, thereby
depositing the noble metal at the surface of the catalyst
precursor structure.
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[0032] The present invention is also directed to methods for
preparing catalysts comprising copper, platinum, and a porous
carbon support.
[0033] In one embodiment, the method comprises contacting the
support with a copper deposition bath comprising copper ions and a
coordinating agent in the absence of an externally applied
voltage, thereby depositing copper at the surface of the porous
carbon support to form a catalyst precursor structure having one
or more regions of deposited copper at the surface of the support;
and contacting the catalyst precursor structure and a platinum
deposition bath comprising platinum ions, thereby depositing
platinum at the surface of the catalyst precursor structure by
displacement of copper from one or more of the regions.
[0034] In another embodiment, the method comprises contacting
the support and a copper deposition bath comprising copper ions in
the absence of an externally applied voltage, thereby depositing
copper at the surface of the carbon support to form a catalyst
precursor structure having one or more regions of deposited copper
at the surface of the support, wherein the carbon support has a
Langmuir surface area of at least about 500 m2/g prior to
deposition of copper thereon; and contacting the catalyst
precursor structure and a platinum deposition bath comprising
platinum ions, thereby depositing platinum at the surface of the
catalyst precursor structure by displacement of copper from one or
more of the regions.
[0035] In a further embodiment, the method comprises
contacting the support and a copper deposition bath comprising
copper ions in the absence of an externally applied voltage,
thereby depositing copper at the surface of the carbon support to
form a catalyst precursor structure having one or more regions of
deposited copper at the surface of the support; contacting the
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catalyst precursor structure and a platinum deposition bath
comprising platinum ions, thereby depositing platinum at the
surface of the catalyst precursor structure by displacement of
copper from one or more of the regions; and heating the surface of
the catalyst precursor having platinum at the surface of the one
or more copper regions to a temperature of at least about 500 C in
a non-oxidizing environment.
[0036] The present invention is also directed to methods for
preparing catalysts comprising iron, platinum, and a porous carbon
support.
[0037] In one embodiment, the method comprises contacting the
support with an iron deposition bath comprising iron ions and a
coordinating agent in the absence of an externally applied
voltage, thereby depositing iron at the surface of the porous
carbon support to form a catalyst precursor structure having one
or more regions of deposited iron at the surface of the support;
and contacting the catalyst precursor structure and a platinum
deposition bath comprising platinum ions, thereby depositing
platinum at the surface of the catalyst precursor structure by
displacement of iron from one or more of the regions.
[0038] In another embodiment, the method comprises contacting
the support and an iron deposition bath comprising iron ions in
the absence of an externally applied voltage, thereby depositing
iron at the surface of the carbon support to form a catalyst
precursor structure having one or more regions of deposited iron
at the surface of the support, wherein the carbon support has a
Langmuir surface area of at least about 500 m2/g prior to
deposition of iron thereon; and contacting the catalyst precursor
structure and a platinum deposition bath comprising platinum ions,
thereby depositing platinum at the surface of the catalyst
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precursor structure by displacement of iron from one or more of
the regions.
[0039] In a further embodiment, the method comprises
contacting the support and an iron deposition bath comprising iron
ions in the absence of an externally applied voltage, thereby
depositing iron at the surface of the carbon support to form a
catalyst precursor structure having one or more regions of
deposited iron at the surface of the support; contacting the
catalyst precursor structure and a platinum deposition bath
comprising platinum ions, thereby depositing platinum at the
surface of the catalyst precursor structure by displacement of
iron from one or more of the regions; and heating the surface of
the catalyst precursor having platinum at the surface of the one
or more iron regions in a non-oxidizing environment.
[0040] The present invention is also directed to methods for
treating a porous substrate to prepare a modified porous substrate
having a reduced surface area attributable to pores having a
nominal diameter within a predefined range.
[0041] In one embodiment, the method comprises disposing a
pore blocking agent within pores of the porous substrate having a
nominal diameter within the predefined range, the pore blocking
agent having at least one dimension relative to the opening of the
pores having a nominal diameter within the predefined range
sufficient such that the pore blocking agent is preferentially
retained within the pores.
[0042] In another embodiment, the method comprises
introducing a pore blocking compound into the pores of the porous
substrate, the pore blocking compound being susceptible to a
conformational change such that the pore blocking compound is
retained within pores of the porous substrate having a diameter
within the predefined range.
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[0043] In a further embodiment, the method comprises
introducing into the pores having a nominal diameter within a
predefined range compounds capable of forming a pore blocking
compound having at least one dimension such that the pore blocking
compound is retained within the pores having a nominal diameter
within a predefined range.
[0044] The present invention is also directed to methods for
treating porous substrates having micropores and larger diameter
pores to prepare a modified porous substrate having a reduced
micropore surface area.
[0045] In one embodiment, the method comprises disposing a
pore blocking agent within micropores of the porous substrate, the
pore blocking agent having at least one dimension relative to the
micropore openings such that the pore blocking agent is
preferentially retained within the pores.
[0046] In another embodiment, the method comprises
introducing a pore blocking compound into the micropores of the
porous substrate, the pore blocking compound being susceptible to
a conformational change such that the pore blocking compound is
retained within micropores of the porous substrate.
[0047] In a further embodiment, the method comprises
introducing into the micropores of the substrate compounds capable
of forming a pore blocking compound having at least one dimension
such that the pore blocking compound is retained within the
micropores.
[0048] In a still further embodiment, the method comprises
introducing a pore blocking composition into the micropores of the
porous substrate, the pore blocking composition comprising a
substituted cyclohexane derivative.
[0049] The present invention is also directed to methods for
preparing a catalyst comprising a metal at the surface of a porous
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substrate wherein the metal is preferentially excluded from pores
of the porous substrate having a nominal diameter within a
predefined range. In one embodiment, the method comprises (i)
introducing one or more precursors of a pore blocking compound
into pores of the porous substrate, wherein: at least one of the
pore blocking compound precursors is susceptible to a
conformational change to form a pore blocking compound that is
retained within pores of the porous substrate having a nominal
diameter within the predefined range, or at least two pore
blocking compound precursors are capable of forming a pore
blocking compound having at least one dimension such that the pore
blocking compound is retained within pores of the porous substrate
having a nominal diameter within a predefined range; (ii)
preferentially removing the pore blocking compound from the pores
of the porous substrate having a nominal diameter outside the
predefined range to prepare a modified porous substrate having a
reduced surface area attributable to pores having a nominal
diameter within the predefined range; and (iii) contacting the
surface of the modified porous substrate with a solution
containing the metal.
[0050] In another embodiment, the present invention is
directed to a porous substrate having a pore blocking compound
within pores of the porous substrate having a nominal diameter
within a predefined range. The pore blocking compound is retained
within the pores having a nominal diameter within a predefined
range due to the pore blocking compound having at least one
dimension that is greater than openings of the pores having a
nominal diameter within a predefined range, or the pore blocking
compound exhibiting a conformation that prevents the pore blocking
compound from exiting through openings of pores having a nominal
diameter within the predefined range.
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[0051] The present invention is directed to treated porous
substrates having a pore blocking compound within micropores of
the porous substrate. In one embodiment, the micropore surface
area of the treated substrate is no more than about 70% of the
micropore surface area of the porous substrate prior to treatment.
In another embodiment, the pore blocking compound is selected from
the group consisting of the condensation product of a substituted
cyclohexane derivative and a glycol, the condensation product of a
di-substituted cyclohexane derivative and a glycol, and
combinations thereof.
[0052] Other objects and features will be in part apparent
and in part pointed out hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] Figs. 1A-1C are graphical representations of pore
blockers in accordance with the present invention.
[0054] Fig. 1D illustrates a conformational change of a pore
blocker in accordance with the present invention.
[0055] Fig. 2 depicts heat treatment of a first and second
metal-impregnated support in accordance with the present
invention.
[0056] Figs. 3A/5A and 3B/5B transmission electron microscopy
(TEM) results as described in Example 3.
[0057] Figs. 4A and 4B provide pore volume and surface area
for treated and untreated substrates as described in Example 4.
[0058] Fig. 5C provides porosity data for catalysts analyzed
as described in Example 19.
[0059] Fig. 5D provides pore volume results for catalysts
analyzed as described in Example 20.
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[0060] Figs. 6-13 are micrographs generated by scanning
transmission electron microscopy (STEM) analysis for a carbon
support and metal-impregnated supports as described in Example 21.
[0061] Fig. 14 provides results of line scan analysis for a
metal-impregnated support as described in Example 21.
[0062] Figs. 15 and 16 are STEM micrographs for catalysts as
described in Example 21.
[0063] Figs. 17 and 18 are results of energy dispersive
spectroscopy (EDS) analysis of catalysts as described in Example
21.
[0064] Figs. 19-21 are STEM micrographs for reaction-tested
catalysts as described in Example 21.
[0065] Fig. 22 provides results of line scan analysis for a
reaction-tested catalyst as described in Example 21.
[0066] Figs. 23 and 24 are STEM micrographs for reaction-
tested catalysts as described in Example 21.
[0067] Fig 25 provides results of line scan analysis for a
reaction tested catalyst as described in Example 21.
[0068] Figs. 26 and 27 are EDS spectra for reaction-tested
catalysts as described in Example 21.
[0069] Figs. 28 and 29 are TEM and STEM images for metal-
impregnated supports as described in Example 22.
[0070] Figs. 30-31, 32-33, 34-35, and 36-37 are TEM images
and corresponding line scan analysis results for metal-impregnated
supports as described in Example 22.
[0071] Figs. 38 and 39 are TEM and STEM images for catalysts
as described in Example 22.
[0072] Fig. 40 indicates the portion of catalyst analyzed by
line scan analysis as described in Example 22.
[0073] Fig. 41 provides line scan analysis for the portion of
the support identified in Fig. 40.
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[0074] Fig. 42 indicates the portion of catalyst analyzed by
line scan analysis as described in Example 22.
[0075] Fig. 43 provides line scan analysis for the portion of
the support identified in Fig. 40.
[0076] Figs. 44 and 45 are TEM images utilized in particle
size analysis as described in Example 23.
[0077] Fig. 46 provides particle size distribution data for
catalyst analyzed as described in Example 23.
[0078] Figs. 47 and 48 are TEM images utilized in particle
size analysis as described in Example 23.
[0079] Fig. 49 provides particle size distribution data for
catalyst analyzed as described in Example 23.
[0080] Figs. 50 and 51 are X-ray diffraction results for a
catalyst analyzed as described in Example 24.
[0081] Figs. 52-55 are nano-diffraction results for a metal
particle analyzed as described in Example 24.
[0082] Fig. 56 and 57 provide reaction testing data as
described in Example 25.
[0083] Fig. 58 provides reaction testing data of Example 26.
[0084] Figs. 59-62 provide reaction testing data of Example
27.
[0085] Figs. 63-65 provide reaction testing data of Example
28.
[0086] Figs. 66-68 provide reaction testing data of Example
29.
[0087] Figs. 69-71 provide reaction testing data of Example
30.
[0088] Figs. 72-78 provide reaction testing data of Example
31.
[0089] Figs. 79-84 provide reaction testing data of Example
32.
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[0090] Fig. 85 provides reaction testing data of Example 33.
[0091] Figs. 86-90 provide reaction testing data of Example
34.
[0092] Figs. 91-95 provide reaction testing data of Example
35.
[0093] Figs. 96-98 provide reaction testing data of Example
36.
[0094] Fig. 99 provides reaction testing data of Example 37.
[0095] Fig. 100 provides reaction testing data of Example 38.
[0096] Figs. 101 and 102 provide reaction testing data of
Example 39.
[0097] Fig. 103 provides platinum site density data as
described in Example 20.
[0098] Fig. 104 provides reaction testing data of Example 41.
[0099] Figs. 105 and 106 provide reaction testing data of
Example 42.
[00100] Fig. 107 provides reaction testing data of Example 43.
[00101] Fig. 108 provides reaction testing data of Example 44.
[00102] Fig. 109 provides X-Ray Diffraction (XRD) results for
the catalyst described in Example 45.
[00103] Figs. 110 and 111 provide XRD results for the catalyst
described in Example 46.
[00104] Fig. 111A provides platinum leaching data for
catalysts described in Examples 46 and 48.
[00105] Figs. 112-115 provide XRD results for the catalysts
described in Example 50.
[00106] Fig. 116 is a scanning transmission electron
microscopy (STEM) micrograph described in Example 55.
[00107] Figs. 117 and 118 are energy dispersive x-ray (EDX)
spectroscopy line scan results described in Example 55.
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[00108] Figs. 119 and 120 are STEM photomicrographs described
in Example 55.
[00109] Fig. 121 is an STEM micrograph described in Example
55.
[00110] Fig. 122 provides electron energy loss spectroscopy
(EELS) line scan results described in Example 55.
[00111] Fig. 123 is an STEM micrograph described in Example
55.
[00112] Fig. 124 provides EELS line scan results described in
Example 55.
[00113] Fig. 125 is an STEM micrograph described in Example
55.
[00114] Fig. 126 provides EELS line scan results described in
Example 55.
[00115] Fig. 127 provides high resolution electron microscopy
(HREM) photomicrographs described in Example 57.
[00116] Fig. 128 provides STEM micrographs described in
Example 57.
[00117] Fig. 129 is an STEM micrograph described in Example
57.
[00118] Fig. 130 provides EDX line scan analysis results
described in Example 57.
[00119] Fig. 131 is an STEM micrograph described in Example
57.
[00120] Fig. 132 provides EDX line scan analysis results
described in Example 57.
[00121] Fig. 133 is an STEM photomicrograph described in
Example 57.
[00122] Fig. 134 provides results of EELS line scan analysis
described in Example 57.
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[00123] Figs. 135-137 are HREM photomicrographs described in
Example 57.
[00124] Fig. 138 provides XRD results described in Example 57.
[00125] Fig. 139 is an STEM micrograph described in Example
60.
[00126] Fig. 140 provides results of EELS line scan analysis
described in Example 60.
[00127] Fig. 141 is an STEM micrograph described in Example
60.
[00128] Fig. 142 provides EDX line scan analysis results
described in Example 60.
[00129] Fig. 143 is an STEM micrograph described in Example
60.
[00130] Fig. 144 provides results of EELS line scan analysis
described in Example 60.
[00131] Fig. 145 provides EDX line scan analysis results
described in Example 60.
[00132] Fig. 146 is an STEM micrograph described in Example
60.
[00133] Fig. 147 provides EDX line scan analysis results
described in Example 60.
[00134] Fig. 148 provides XRD results described in Example 60.
[00135] Figs. 149 and 150 are STEM micrographs described in
Example 60.
[00136] Fig. 151 provides EDX line scan analysis results
described in Example 60.
[00137] Fig. 152 is an STEM micrograph described in Example
60.
[00138] Fig. 153 provides EDX line scan analysis described in
Example 60.
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[00139] Figs. 154 and 155 provide XRD results described in
Example 61.
[00140] Figs. 155A and 155B provide microscopy results for a
finished catalyst as described in Example 65.
[00141] Figs. 155C - 155F provide microscopy results for a
finished catalyst described in Example 65.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[00142] Described herein are catalyst preparation methods
providing improvements in metal utilization in supported, metal-
containing catalysts. Generally, various embodiments of the
present invention include controlling and/or directing metal
deposition onto the surface of a porous substrate. Controlling or
directing metal deposition can be used to address one or more
problems associated with the preparation of conventional
supported, metal-containing catalysts.
[00143] For example, one potential drawback associated with
conventional platinum on carbon catalysts is the susceptibility of
relatively small platinum-containing particles to leaching during
liquid phase catalytic oxidation reactions as compared to larger
metal-containing particles. Excessive leaching of metal particles
results in metal loss and represents inefficient metal usage.
Furthermore, in the case of PMIDA oxidation, these relatively
small platinum-containing crystallites are believed to contribute
to undesired by-product formation (e.g., IDA). Relatively small
platinum-containing crystallites are also believed to be more
susceptible to deactivation than larger particles (e.g., by
deactivation of metal-containing active sites in the presence of
the reaction medium and/or by coking of the catalyst). It is
believed that a significant portion of the relatively small metal
particles are at the surface of the carbon support within
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relatively small pores and that the small pores may act to trap
and prevent these relatively small platinum crystallites from
agglomerating into larger particles that are generally more
resistant to leaching and generally do not promote IDA formation.
In addition, metal deposited at the surface of a porous substrate
within the relatively small pores is believed to be less
accessible to reactants than metal deposited within larger pores,
and thereby contributes less to catalyst activity.
[00144] Various methods described herein for directing and/or
controlling metal deposition generally involve treating porous
substrates by disposing or introducing one or more pore blocking
compounds within pores of a predefined size range. The methods
described herein may be used to selectively block pores within a
certain size domain without significantly affecting other pores of
the substrate so as to provide advantageous catalytic surface
area. As detailed herein, including the Examples, various
embodiments of the present invention provide a porous substrate
including a pore blocking compound disposed and preferentially
retained within relatively small pores (e.g., micropores, or pores
having a nominal diameter of less than about 20A). The presence
of the pore blocking compound within the pores of the substrate
may be indicated by a reduced proportion of surface area
attributable to the relatively small pores (e.g., a reduced
proportion of micropore surface area) and/or by a reduced
contribution to the porosity of the substrate by the relatively
small pores. It is believed that the presence of the pore
blocking compound within the micropores of the treated substrate
reduces, and preferably substantially prevents, metal deposition
at the substrate surfaces within these pores, thereby directing
metal deposition to other surfaces of the substrate and within
larger pores. The presence of the pore blocker is thus currently
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believed to reduce formation of small metal crystallites within
the micropores that are resistant to agglomeration, readily
leached and/or deactivated, and represent inefficient metal usage.
[00145] In addition to or separate from the effect of
controlling or directing the location of metal deposition (e.g.,
by disposing within or introducing a pore blocking compound into
pores of a substrate), the manner of metal deposition may promote
more efficient metal usage as well. For example, various
catalysts described herein include and/or are prepared from a
support having one or more regions of a first metal at the surface
of the support, and a second metal at the surface of the one or
more regions of the first metal.
[00146] The first metal is selected to have a greater
electropositivity than the second metal and the second metal is
deposited at the surface of the one or more regions of the first
metal by displacement of the first metal from the one or more
regions at the surface of the support. More particularly, the
second metal may be deposited by near atom-for-atom replacement of
the first metal by the second metal. It is currently believed
that metal deposition in this manner promotes formation of a
relatively thin layer comprising second metal atoms and may in
fact form a near monolayer of second metal atoms deposited at the
surface of the first metal regions (e.g., a layer of second metal
atoms at the surface of the one or more regions of first metal no
more than about 3 atoms thick). Heating the carbon support having
the first and second metals thereon forms metal particles
comprising the first and second metal. The metal particles formed
contain the second metal in a form that represents more efficient
second metal utilization. For example, the composition of a
significant fraction of the metal particles is generally rich in
first metal content, thereby providing a relatively low proportion
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of unexposed second metal throughout the particles (e.g., a first
metal-rich bimetallic alloy). Additionally or alternatively,
metal particles formed upon subsequent heating may have a
relatively thin shell comprising the second metal (e.g., a layer
no more than about 3 atoms thick) at least partially surrounding a
core predominantly comprising the first metal.
I. Porous Substrate Treatment
[00147] Disposing within and/or introducing a pore blocking
agent or compound (also referred to herein as a pore blocker) into
pores of a porous substrate generally comprises contacting the
substrate with the agent or compound, or a precursor (or
precursors) thereof. In one embodiment, the pore blocking
compound is preferentially retained within pores of the substrate
within a selected size domain (e.g., micropores) by virtue of
having at least one dimension larger than the openings of the
pores, thereby inhibiting the agent from exiting the selected
pores. In various embodiments, the pore blocking agent may be
formed from one or more pore blocking agent precursors introduced
into the substrate pores. Additionally or alternatively, and
regardless of whether the pore blocking agent is introduced into
the pores or formed in situ (i.e., formed from one or more agent
precursors introduced into the pores), the agent may be retained
within pores of the substrate within a selected size domain by
virtue of an induced conformational change in the pore blocking
agent such that the pore blocking agent is dimensionally inhibited
from exiting the selected pores. A conformational change in the
pore blocking agent may be induced within selected pores by virtue
of interactions between the pore blocking agent and the walls of
the pores. In accordance with one embodiment, a pore blocking
agent is disposed within and preferentially retained within
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micropores of the porous substrate to produce a treated substrate
for metal deposition exhibiting a reduced proportion of micropore
surface area.
[00148] It is to be understood that reference to one or more
precursors contemplates compositions that ultimately function as a
pore blocking agent upon entry into pores (e.g., by virtue of at
least one dimension of the compound and/or by virtue of a
conformational change in the compound after entry into the pores).
Additionally or alternatively, reference to one or more precursors
may refer to one or more compounds that combine or react to form
the pore blocking agent once disposed within and/or introduced
into the pores of the substrate. Regardless of whether a compound
that ultimately functions as the pore blocker is introduced into
or disposed within the pores of the substrate, or whether
components that combine to form the pore blocker are introduced
into or disposed within the pores, the mechanism by which the pore
blocker is believed to function (i.e., by virtue of having at
least one dimension larger than pore openings, either initially or
following a conformational change) is the same.
[00149] In various embodiments the pore blocker comprises a
compound having at least one dimension such that, after entry into
pores, the pore blocker is preferentially retained within those
pores falling within a selected size domain. Of course, it is to
be understood that the pore blocker likewise typically has at
least one dimension that permits entry into the pores, but it is
currently believed that the pore blocker typically assumes an
orientation and/or conformation within the pores such that the
dimension greater than the pore opening prevents the pore blocking
compound from exiting the pore.
[00150] As noted above, in accordance with one embodiment, the
pore blocker is preferentially retained within substrate
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micropores. However, this does not exclude the pore blocker or
precursor(s) thereof from also entering pores of a size that are
not within this predefined range upon contact with the porous
substrate. For example, pore blocker may enter pores having a
nominal diameter greater than about 20A (e.g., pores having a
nominal diameter of from about 20A to about 3000A, commonly
referred as meso- and macropores), but the pore blacker tends to
subsequently exit and not be preferentially retained within these
pores, although the pore blocking agent may remain in a minor
portion of pores outside the micropore range.
A. Porous Substrate
[00151] Generally, the porous substrate or supporting
structure for the catalytic metal-containing active phase may
comprise any material suitable for deposition of one or more
metals thereon. Preferably, the porous substrate is in the form
of a carbon support. In general, the carbon supports used in the
present invention are well known in the art including, for
example, those detailed in U.S. Patent No. 6,417,133 to Ebner at
al. and by Wan et al. in WO 2006/031938.
Activated, non-graphitized carbon supports are
preferred for noble metal on carbon catalysts used for PMIDA
oxidation and provide the catalyst with robust mechanical
integrity and high surface area for the metal-containing active
phase. However, activated, non-graphitized carbon supports are
not necessarily preferred in all instances and it should be
understood that suitable catalysts for various other applications
may be prepared utilizing carbon supports that are not activated
and/or non-graphitized. In various particularly preferred
=
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embodiments, the supports are in the form of particulates (e.g.,
powders).
[00152] In various preferred embodiments (e.g., catalysts used
for PMIDA oxidation), the carbon support contains a relatively low
proportion of oxygen-containing functional groups (e.g.,
carboxylic acids, ethers, alcohols, aldehydes, lactones, ketones,
esters, amine oxides, and amides). These functional groups may
increase noble metal leaching and potentially increase noble metal
agglomeration and particle growth during liquid phase oxidation
reactions and thus reduce the ability of the catalyst to oxidize
oxidizable substrates (e.g., PMIDA and/or formaldehyde). As used
herein, an oxygen-containing functional group is "at the surface
of the carbon support" if it is bound to an atom of the carbon
support and is able to chemically or physically interact with
compositions within the reaction mixture or with the metal atoms
deposited on the carbon support. As described in U.S. Patent No.
6,417,133 and by Wan et al. in WO 2006/031938, many of the oxygen-
containing functional groups that reduce noble metal resistance to
leaching and sintering and reduce the activity of the catalyst
desorb from the carbon support as carbon monoxide when the
catalyst is heated at a high temperature (e.g., 900 C) in an inert
atmosphere (e.g., helium or argon). Thus, measuring the amount of
CO desorption from a fresh catalyst (i.e., a catalyst that has not
previously been used in a liquid phase oxidation reaction) under
high temperatures is one method that may be used to analyze the
surface of the catalyst to predict noble metal retention and
maintenance of catalyst activity. One way to measure CO
desorption is by using thermogravimetric analysis with in-line
mass spectroscopy ("TGA-MS"). Preferably, no more than about 1.2
mmole of carbon monoxide per gram of catalyst desorb from the
catalyst of the present invention when a dry, fresh sample of the
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catalyst, after being heated at a temperature of about 500 C for
about 1 hour in a hydrogen atmosphere and before being exposed to
an oxidant following the heating in the hydrogen atmosphere, is
heated in a helium atmosphere is subjected to a temperature which
is increased from about 20 C to about 900 C at about 10 C per
minute, and then held constant at about 900 C for about 30 minutes.
More preferably, no more than about 0.7 mmole of carbon monoxide
per gram of fresh catalyst desorb under those conditions, even
more preferably no more than about 0.5 mmole of carbon monoxide
per gram of fresh catalyst desorb, and most preferably no more
than about 0.3 mmole of carbon monoxide per gram of fresh catalyst
desorb. A catalyst is considered "dry" when the catalyst has a
moisture content of less than about 1% by weight. Typically, a
catalyst may be dried by placing it into a N2 purged vacuum of
about 25 inches of Hg and a temperature of about 120 C for about 16
hours.
[00153] As further described in U.S. Patent No. 6,417,133 and
by Wan et al. in WO 2006/031938, measuring the number of oxygen
atoms at the surface of a fresh catalyst support is another method
to analyze the catalyst to predict noble metal retention and
maintenance of catalytic activity. Using, for example, x-ray
photoelectron spectroscopy, a surface layer of the support which
is about 50 A in thickness is analyzed. Preferably, this analysis
for a support suitable for use in connection with the oxidation
catalysts described herein indicates a ratio of carbon atoms to
oxygen atoms at the surface of the support of at least about 20:1.
More preferably, the ratio is at least about 30:1, even more
preferably at least about 40:1, even more preferably at least
about 50:1, and most preferably at least about 60:1. In addition,
the ratio of oxygen atoms to metal atoms at the surface preferably
is less than about 8:1. More preferably, the ratio is less than
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about 7:1, even more preferably less than about 6:1, and most
preferably less than about 5:1.
[00154] Typically, a support that is in particulate form may
comprise a broad size distribution of particles. For powders,
preferably at least about 95% of the particles are from about 2 to
about 300 m in their largest dimension, more preferably at least
about 98% of the particles are from about 2 to about 200 m in
their largest dimension, and most preferably about 99% of the
particles are from about 2 to about 150 m in their largest
dimension with about 95% of the particles being from about 3 to
about 100 m in their largest dimension. Particles greater than
about 200 m in their largest dimension tend to fracture into
super-fine particles (i.e., less than 2 m in their largest
dimension), which may be more difficult to recover.
[00155] In the following discussion, specific surface areas of
carbon supports and catalysts are typically provided in terms of
the well-known Langmuir method using N2. It is to be understood
that these values generally correspond to those measured by the
likewise well-known Brunauer-Emmett-Teller (B.E.T.) method using
N2 =
[00156] The specific surface area of the carbon support prior
to any treatment (e.g., disposing or introducing a pore blocking
compound within pores of a substrate) in accordance with the
present invention is generally at least about 500 m2/g, at least
about 750 m2/g, at least about 1000 m2/g, or at least about 1250
m2/g. Typically, the specific surface area of the carbon support
is from about 10 to about 3000 m2/g, more typically from about 500
to about 2100 m2/g, and still more typically from about 750 to
about 1900 m2/g or from about 1000 to about 1900 m2/g. In certain
embodiments, the preferred specific surface area is from about
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1000 to about 1700 m2/g, 1000 to about 1500 m2/g, from about 1100
to about 1500 m2/g, from about 1250 to about 1500 m2/g, from about
1200 to about 1400 m2/g, or about 1400 m2/g. Further in accordance
with the present invention, the porous carbon support generally
has a pore volume of at least about 0.1 ml/g, at least about 0.2
ml/g, or at least about 0.4 ml/g. Typically, the porous carbon
support has a pore volume of from about 0.1 to about 2.5 ml/g,
more typically from about 0.2 to about 2.0 ml/g and, still more
typically, of from about 0.4 to about 1.5 ml/g.
[00157] It is to be noted that the present discussion focuses
on pore blocking treatment to reduce micropore surface area of
porous carbon substrates or supports for use in noble metal-
containing catalysts suitable for use in PMIDA oxidation.
However, it is to be understood that methods for treating a porous
substrate by introduction of a pore blocking compound as described
herein are generally applicable to preferentially blocking other
pore size domains, other types of porous catalyst supports and/or
porous carbon substrates used as supports for metals other than
noble metals. For example, the methods of the present invention
are suitable for treatment of porous Raney metals or alloys often
referred to as sponges, such as those described in U.S. Patent No.
7,329,778 to Morgenstern et al. and used as supports for copper-
containing catalysts used in the dehydrogenation of primary amino
alcohols. By way of further example, the methods of the present
invention are also suitable for treatment of other non-carbon
porous supports such as, for example, silicon dioxide (Si02),
aluminum oxide (A1203), zirconium oxide (Zr03), titanium oxide
(Ti02), and combinations thereof.
B. Pore Blocking
[00158] In accordance with the present invention, the pore
blocker used to selectively block micropores may be selected from
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a variety of compounds including, for example, various sugars
(e.g., sucrose), 5- or 6-member ring-containing compounds (e.g.,
1,3- and 1,4-disubstituted cyclohexanes), and combinations
thereof. Compounds suitable for use in connection with selective
blocking of micropores include 1,4-cyclohexanedimethanol (1,4-
CHDM), 1,4-cyclohexanedione bis(ethylene ketal), 1,3- or 1,4-
cyclohexanedicarboxylic acid, 1,4-cyclohexane dione monoethylene
acetal, and combinations thereof.
[00159] In various embodiments, the pore blocker may comprise
the product of a reaction (e.g., a condensation reaction) between
one or more pore blocking compound precursors. Once formed, the
resulting pore blocking compound may be preferentially retained
within selected pores of the substrate by virtue of having at
least one dimension that prevents the pore blocking compound from
exiting the pores.
[00160] For example, it has been observed that the coupling
product of a cyclohexane derivative and a glycol may be utilized
as a micropore pore blocking agent for particulate carbon
substrates used to support a noble metal or other metal catalyst.
More particularly, the pore blocking agent may be the coupling
product of a di-substititued, tri-substituted, or tetra-
substituted cyclohexane derivative and a glycol. In particular,
the cyclohexane derivative may be selected from the group
consisting of 1,4-cyclohexanedione, 1,3-cyclohexanedione, 1,4-
cyclohexanebis(methylamine), and combinations thereof. The glycol
is generally selected from the group consisting of ethylene
glycol, propylene glycol, and combinations thereof.
[00161] Generally, the substrate is contacted with a liquid
comprising the pore blocking agent or one or more precursor(s) of
the pore blocking agent. Typically, the substrate to be treated
is contacted with a mixture or solution comprising one or more
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pore blocking compounds or precursor(s) dispersed or dissolved in
a liquid contacting medium (e.g., deionized water). For example,
the substrate may be contacted with a mixture or solution
including a cyclohexane derivative and a glycol, or a liquid
contacting medium consisting essentially of the cyclohexane
derivative and glycol. The substrate may also be sequentially
contacted with liquids or liquid media comprising one or more of
the precursors. The composition of the liquid including the pore
blocking agent or a precursor(s) thereof contacted with the porous
substrate is not narrowly critical and may be readily selected
and/or optimized by one skilled in the art.
[00162] As noted, regardless of whether a compound that
ultimately functions as a pore blocker is introduced into pores of
the substrate or precursors that form the blocking compound are
introduced into the substrate, pore blockers may be preferentially
retained within selected substrate pores (e.g., micropores) by
virtue of the conformational arrangement assumed by the pore
blocking agent once disposed or formed within the pores. For
example, it is currently believed that various pore blocker
molecules transform from a more linear chair conformation to a
bulkier boat conformation, which conduces trapping of the compound
within the micropores. In particular, it is currently believed
that various pore blocking agents including a hydrophilic end
group will favor a boat conformation within the micropore(s) of a
porous carbon support because of the nature of the carbon support
(i.e., the boat conformation will be favored by a pore blocking
compound having hydrophilic end groups because of the relatively
hydrophobic nature of the carbon support surface). Examples of
pore blocking compounds including a hydrophilic end group include
1,4-cyclohexanedicarboxylic acid and 1,4-cyclohexanedimethanol
(CHDM).
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[00163] A conformational change of a pore blocker also may be
promoted or induced by manipulating the liquid medium comprising
the pore blocking agent in contact with the substrate including,
for example, adjusting the pH and/or adjusting the temperature of
the liquid medium.
[00164] Figs. 1A-1C provide graphical representations of pre-
formed pore blockers and pore blocker molecules formed from
precursors within the pore (i.e., in situ coupling) that undergo a
conformational change within the pore to selectively block or plug
smaller pores. Conformational change of a cyclohexane pore
blocker is shown generally in Fig. 1D. These depictions are for
illustrative purposes and are not intended to limit the present
invention.
[00165] As noted, it is believed that contacting the substrate
with the pore blocking agent or precursors results in pore
blocking agent being introduced into or disposed within substrate
micropores, and within larger pores outside this predefined range.
In order to provide a treated substrate in which the micropores
within the predefined range are preferentially blocked, the
substrate is subsequently contacted with a washing liquid to
remove the blocking agent from pores outside the micropore domain
(i.e., those pores in which the pore blocking agent will not be
preferentially retained by virtue of the agent having at least one
dimension larger than the pore opening). The precise composition
of the washing liquid and manner of its contact with the substrate
are not narrowly critical, but the substrate may suitably be
contacted with deionized water for this purpose.
C. Treated Substrates
[00166] As noted, the substrate treatment method of the
present invention is suitable for introducing a pore blocking
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agent into the micropores of porous substrates (e.g., a
particulate carbon support) and preferentially retaining the pore
blocking agent in the micropores. Preferential retention of the
pore blocking agent within micropores may be represented by the
proportion of micropores in which the agent is retained.
Typically, the pore blocking compound remains in at least about
2%, at least about 5%, at least about 10%, or at least about 20%
of the micropores, basis the total number of substrate micropores.
[00167] Preferential retention of the pore blocking compound
within micropores may also be indicated by the treated substrate
surface area provided by micropores and provided by larger pores.
It is believed that the presence of the pore blocking compound
within micropores will cause at least a portion of these "blocked"
pores to appear as a non-porous portion of the treated substrate
during surface area measurement methods (e.g., the well-known
Langmuir surface area measuring method), thereby reducing the
proportion of surface area that would otherwise be attributable to
the micropores if they were not blocked. This preferential
blocking of the targeted pores results in a reduction in the
surface area provided by the micropores (i.e., micropore surface
area). For example, in various embodiments, the micropore surface
area of the treated substrate is generally no more than about 70%,
no more than about 60%, or no more than about 50% of the micropore
surface area of the substrate prior to treatment by contact with
the pore blocker. Preferably, the micropore surface area of the
treated substrate is no more than about 40%, more preferably no
more than about 30% and, still more preferably, no more than about
20% of the micropore surface area of the substrate prior to
treatment.
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D. Methods for Preparing Catalysts Using Treated
Substrates
[00168] As detailed herein, catalysts may be prepared by a
process generally comprising depositing one or more noble metals
and optionally one or more promoter metals at the surface of a
treated (i.e., pore blocked) substrate such as a porous carbon
support and heating the carbon support having the noble metal and
optional promoter(s) deposited thereon in a non-oxidizing
environment.
[00169] The noble metal is generally selected from the group
consisting of platinum, palladium, ruthenium, rhodium, iridium,
silver, osmium, gold, and combinations thereof. In various
preferred embodiments, the noble metal comprises platinum and/or
palladium. In still further preferred embodiments, the noble
metal is platinum. One or more promoter metals is generally
selected from the group consisting of tin, cadmium, magnesium,
manganese, nickel, aluminum, cobalt, bismuth, lead, titanium,
antimony, selenium, iron, rhenium, zinc, cerium, zirconium,
tellurium, germanium, and combinations thereof at a surface of the
porous substrate and/or a surface of the noble metal.
[00170] The noble metal may be deposited in accordance with
conventional methods known in the art including, for example,
liquid phase deposition methods such as reactive deposition
techniques (e.g., deposition via reduction of noble metal
compounds and deposition via hydrolysis of noble metal compounds),
ion exchange techniques, excess solution impregnation, and
incipient wetness impregnation; vapor phase methods such as
physical deposition and chemical deposition; precipitation;
electrochemical deposition; and electroless deposition as
described in U.S. Patent No. 6,417,133 and by Wan et al. in
International Publication No. WO 2006/031938. In various
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preferred embodiments, the noble metal is deposited via a reactive
deposition technique comprising contacting the carbon support with
a solution comprising a salt of the noble metal, and then
hydrolyzing the salt. An example of a relatively inexpensive
suitable platinum salt is hexachloroplatinic acid (H2PtC16).
[00171] A promoter(s) may be deposited onto the surface of the
treated carbon support before, simultaneously with, or after
deposition of the noble metal onto the surface. Methods to deposit
a promoter metal are generally known in the art, and include the
methods noted above regarding noble metal deposition.
[00172] After the carbon support has been impregnated with the
noble metal(s) and optional promoter(s), the surface of the
catalyst is preferably heated to elevated temperatures, for
example, in a heat treatment or calcining operation. For example,
calcining may be carried out by placing the catalyst in a kiln
(e.g., rotary kilns, tunnel kilns, and vertical calciners) through
which a heat treatment atmosphere is passed.
[00173] Generally, the surface of the treated support
impregnated with one or more metals is heated to a temperature of
at least about 700 C, at least about 800 C, at least about 850 C,
at least about 900 C, or at least about 950 C. Typically, the
metal-impregnated support is heated to a temperature of from about
800 C to about 1200 C, preferably from about 850 C to about 1200 C,
more preferably from about 900 C to about 1200 C, even more
preferably from about 900 C to about 1000 C and especially from
about 925 C to about 975 C.
[00174] The period of time that the impregnated support is
subjected to elevated temperatures (including the time at which
the support is heated at the maximum temperature) is not narrowly
critical. Typically, in commercial scale apparatus, the metal-
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impregnated support is heated at the maximum heat treatment
temperature for at least about 10 minutes (e.g., at least about 30
minutes).
[00175] Preferably, the metal-impregnated support is heated in
a non-oxidizing environment. The non-oxidizing environment may
comprise or consist essentially of inert gases such as N2, noble
gases (e.g., argon, helium) or mixtures thereof. In certain
embodiments, the non-oxidizing environment comprises a reducing
environment and includes a gas-phase reducing agent such as, for
example, hydrogen, carbon monoxide, or combinations thereof. The
non-oxidizing environment in which the catalyst is heated may
include other components such as ammonia, water vapor, and/or an
oxygen-containing compound as described, for example, by Wan et
al. in International Publication No. WO 2006/031938. In one
embodiment, heat treatment following metal deposition preferably
comprises high-temperature gas-phase reduction to remove oxygen-
containing functional groups from the surface of the catalyst,
thereby attaining a catalyst exhibiting the carbon monoxide
desorption and/or carbon atom to oxygen atom surface ratio
characteristics as described in Ebner et al. U.S. Patent No.
6,417,133.
[00176] In various preferred embodiments, the noble metal is
alloyed with at least one promoter to form alloyed metal
particles. For example, noble metal particles at a surface of the
carbon support may comprise noble metal atoms alloyed with
promoter metal atoms. In various other preferred embodiments, the
noble metal is alloyed with two promoters (e.g., iron and cobalt).
Catalysts comprising a noble metal alloyed with one or more
promoters often exhibit greater resistance to metal leaching and
further stability (e.g., from cycle to cycle) with respect to
formaldehyde and formic acid oxidation. It is to be understood
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that the term alloy as used herein generally encompasses any metal
particle comprising a noble metal and at least one promoter (e.g.,
intermetallic compounds, substitutional alloys, multiphasic
alloys, segregated alloys, and interstitial alloys as described by
Wan et al. in International Publication No. WO 2006/031938).
[00177] Subjecting the metal-impregnated support to heat
treatment generally provides agglomeration and/or sintering of
metal particles at the surface of the support. Utilizing treated
substrates having blocked micropores results in impregnated
supports having a reduced proportion of relatively small metal-
containing particles at the support surface within the micropore
domain, which are generally more susceptible to leaching and/or
deactivation, as compared to larger-sized noble metal-containing
particles. Additionally or alternatively, metal-containing
particles at the substrate surface outside the micropore domain
are generally more accessible to reactants. By virtue of either
or both of these effects, treated substrates of the present
invention are believed to provide more efficient metal usage
(e.g., an increase in effective catalytic metal surface area per
unit weight) in the catalyst.
[00178] It is to be noted that persistence of the pore blocker
in the treated substrate following post-metal deposition heat
treatment is not critical to provide the above-noted advantages.
In fact, it is currently believed that the pore blocker is most
likely decomposed and/or otherwise removed from the substrate
surface during calcining. But it is further currently believed
that one or more of the above-noted advantages are achieved so
long as the pore blocker is preferentially retained with the
selected pores at the support surface during metal deposition in
order to promote the desired metal dispersion.
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E. Catalysts Prepared Using Treated Substrates
[00179] Substrates treated in accordance with the present
method (i.e., pore blocked substrates) may be utilized as supports
for metal-containing catalysts including, for example, catalysts
including one or more noble metals (e.g., a noble metal such as
platinum) deposited on a particulate carbon support. In addition,
noble metal-containing catalysts prepared using substrates treated
by the present invention may include one or more promoter(s) and
may be prepared in a manner to exhibit one or more of the
properties as described, for example, in U.S. Patent No.
6,417,133, International Publication No. WO 2006/031938, and U.S.
Patent No. 6,956,005.
[00180] Generally, the noble metal constitutes less than about
8% by weight of the catalyst, typically less than about 7% by
weight of the catalyst, more typically less than about 6% by
weight of the catalyst. In various embodiments, the noble metal
typically constitutes from about 1% to about 8% by weight of the
catalyst, more typically from about 2% to about 7% by weight of
the catalyst and, still more typically, from about 3% to about 6%
by weight of the catalyst.
[00181] As noted, particulate carbon supports treated in
accordance with the present invention to preferentially block
= micropores provide more efficient metal usage. Accordingly,
effective catalysts may be prepared that contain noble metal in an
amount below the above-noted limits and/or at or near the lower
limits of one or more of the above-noted ranges. For example, in
various embodiments, the noble metal constitutes less than about
5% by weight of the catalyst, less than about 4% by weight of the
catalyst, or even less than about 3% by weight of the catalyst.
By way of further example, in various embodiments the noble metal
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typically constitutes from about 1% to about 5% by weight of the
catalyst, more typically from about 1.5% to about 4% by weight of
the catalyst and, still more typically, from about 2% to about 3%
by weight of the catalyst. However, it should be understood that
the present invention does not require that a treated substrate be
used for preparation of a noble metal-containing catalyst
including a reduced proportion of noble metal as compared to
conventional catalysts. Namely, preparation of a catalyst
including a treated porous substrate that provides more efficient
metal usage at conventional noble metal loadings likewise
represents an advance in the art (e.g., treated substrates of the
present invention are currently believed to provide a reduced
proportion of relatively small metal particles that are
susceptible to leaching and represent inefficient metal usage,
thereby contributing to improvements in catalytic activity and
reduced undesired by-product (e.g., IDA) formation).
[00182] Generally, in accordance with some embodiments, at
least one promoter (e.g., iron) constitutes less than about 2% by
weight of the catalyst, less than about 1.5% by weight of the
catalyst, less than about 1% by weight of the catalyst, less than
about 0.5% by weight of the catalyst, or about 0.4% by weight of
the catalyst. Typically, at least one promoter constitutes less
than about 1% by weight of the catalyst, preferably from about
0.25% to about 0.75% by weight of the catalyst and, more
preferably, from about 0.25% to about 0.6% by weight of the
catalyst. In various preferred embodiments, the catalyst includes
iron as a promoter. Additionally or alternatively, the catalyst
includes cobalt as a promoter.
[00183] In various particularly preferred embodiments, the
catalyst comprises both iron and cobalt promoters. Use of iron
and cobalt generally provides benefits associated with use of iron
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(e.g., activity and stability with respect to formaldehyde and
formic acid oxidation). However, as compared to the presence of
iron alone as a promoter, the presence of cobalt tends to reduce
formation of certain by-products during oxidation of a PMIDA
substrate (e.g., IDA). Moreover, IDA formation is believed to be
directly related to total iron content of the catalyst. Thus, in
various iron/cobalt co-promoter embodiments, iron content is
essentially replaced by cobalt to reduce formation of IDA and
other by-products while nevertheless providing sufficient activity
towards oxidation of formaldehyde and formic acid. For example,
as compared to a platinum on carbon catalyst containing 0.5% by
weight iron in the absence of cobalt, a similar catalyst
containing 0.25% by weight iron and 0.25% by weight cobalt
typically provides comparable activity for PMIDA, formaldehyde and
formic acid oxidation, while minimizing by-product formation.
[00184] In iron/cobalt co-promoter embodiments, the amount of
each promoter at the surface of the carbon support (whether
associated with the carbon surface itself, noble metal, or a
combination thereof) is typically at least about 0.05% by weight,
at least about 0.1% by weight or at least about 0.2% by weight.
Furthermore, the amount of iron at the surface of the carbon
support is typically from about 0.1 to about 4% by weight of the
catalyst, preferably from about 0.1 to about 2% by weight of the
catalyst, more preferably from about 0.1 to about 1% by weight of
the catalyst and, even more preferably, from about 0.1 to about
0.5% by weight of the catalyst. Similarly, the amount of cobalt
at the surface of the carbon support is typically from about 0.1
to about 4% by weight of the catalyst, preferably from about 0.1
to about 2% by weight of the catalyst, more preferably from about
0.2 to about 1% by weight of the catalyst and, even more
preferably, from about 0.2 to about 0.5% by weight of the
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catalyst. In such an embodiment, the weight ratio of iron to
cobalt in the catalyst is generally from about 0.1:1 to about
1.5:1 and preferably from about 0.2:1 to about 1:1. For example,
the catalyst may comprise about 0.1% by weight iron and about 0.4%
by weight cobalt or about 0.2% by weight and about 0.2% by weight
cobalt.
[00185] As understood by those skilled in the art, the metal
content of the catalysts can be freely controlled within the
ranges described herein (e.g., by adjusting the concentration and
relative proportions of the metal source(s) used in a liquid phase
reactive deposition bath).
II. First and Second Metal-Containing Catalysts
[00186] Various preferred embodiments of the present invention
are directed to catalysts that comprise and/or are prepared from a
porous substrate or support having one or more regions of a first
metal at its surface, and a second metal at the surface of the one
or more regions of the first metal. In such embodiments, the
first metal is selected to have an electropositivity greater than
the electropositivity of the second metal (i.e., the first metal
is higher than the second metal in the electromotive series).
Oxidation of the first metal provides electrons for reduction of
second metal ions present in the deposition bath to thereby
deposit second metal atoms at the surface of the one or more
regions of the first metal. The first metal oxidation and second
metal reduction and deposition occur substantially simultaneously
and second metal atoms are deposited at the surface of the one or
more regions of the first metal by displacement of first metal
ions from the one or more regions into the deposition bath. Metal
deposition in this manner may be referred to as spontaneous, or
redox displacement deposition. (See, for example, U.S. Patent No.
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6,670,301 to Adzic et al. and U.S. Patent Nos. 6,376,708,
6,706,662 and 7,329,778 to Morgenstern et al.) Preferably, the
sacrificial first metal is less expensive than the second metal.
[00187] As detailed herein, deposition of the second metal by
displacement deposition is preferably conducted and controlled in
a manner that provides preferential deposition of the second metal
at the surface of the one or more regions of the first metal.
That is, the second metal is preferentially deposited at the
surface of the first metal region(s) by displacement deposition
over deposition of the second metal at the support surface and/or
deposition of the second metal at the surface of already-deposited
second metal.
[00188] Without being bound to a particular theory, it is
currently believed that the source of second metal ions may
promote preferential deposition of the second metal onto the one
or more regions of first metal. More particularly, it is
currently believed that second metal sources that provide second
metal ions at lower oxidation numbers (e.g., +2) provide slower,
more controlled metal deposition as compared to sources that
provide noble metal ions at higher oxidation numbers (e.g., +4).
Second metal ions at such higher oxidation numbers are believed to
be more readily reduced in the presence of electrons generated by
oxidation of the first metal which provides a greater driving
force for deposition of the second metal. This greater driving
force is believed to increase the rate of second metal deposition
which, in turn, is believed to promote less discriminate
deposition of the second metal. More particularly, the greater
driving force for deposition of second metal ions is believed to
promote deposition of second metal atoms onto the support and/or
onto the surface of already-deposited second metal atoms.
Accordingly, it is currently believed that as the oxidation state
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of second metal ions decreases, preferential (e.g., selective)
deposition of the noble metal directed onto one or more regions of
first metal by displacement of first metal atoms over deposition
onto the carbon support and/or already-deposited second metal
atoms generally increases.
[00189] In addition, it is currently believed that deposition
of second metal atoms utilizing sources that provide ions at
relatively low oxidation numbers proceeds in a manner that
generally reduces the complexity of the displacement deposition
process to promote the desired preferential deposition of the
second metal directed onto the first metal regions. For example,
displacement deposition utilizing sources that provide second
metal ions at relatively low oxidation numbers proceeds readily in
the absence of precise control of concentration of the second
metal source and/or deposition time.
[00190] In accordance with the present invention, it is
currently believed that a significant fraction, if not
substantially all, of the second metal deposited by controlled
displacement of a first metal provides domains or regions at the
surface of one or more regions of the first metal characterized as
comprising a relatively thin layer of second metal atoms (e.g., no
more than about 5 atoms thick, or no more than about 3 atoms
thick), rather than agglomerating to form metal-containing
particles. In certain preferred embodiments, preparation of the
catalyst by the present method may provide a near monolayer of
second metal (e.g., a layer of second metal atoms no more than
about 3 atoms in thickness, no more than about 2 atoms in
thickness, and preferably from about one to about two atoms in
thickness).
[00191] Further in accordance with the present invention, it
is currently believed that deposition of the second metal by
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displacement of first metal atoms from one or more regions of
first metal provides a structure (e.g., a catalyst precursor
structure) that, upon heat treatment at elevated temperatures,
provides metal particles that include the second metal in a form
that represents more efficient second metal utilization. In
various embodiments, the metal particles are typically first
metal-rich (i.e., contain an excess of first metal atoms over
second metal atoms) and it is currently believed that the
particles include one or more bimetallic alloys. In contrast,
conventional noble metal-containing catalysts typically include
particles comprising an atomic excess of noble metal atoms. In
this manner, the first metal-rich particles are believed to
include the noble (i.e., second) metal in a form that represents a
reduced proportion of noble metal distributed throughout the
particle and, accordingly, represents reduced unexposed, and
potentially unutilized noble metal atoms throughout the particle
structure. But an excess of first metal is not required to
provide an improvement in metal utilization. However, to the
extent that the proportion of first metal to second metal is
increased, improvements in second metal utilization may be
realized. Accordingly, various embodiments of the present
invention contemplate selecting first and second metal
combinations that are amenable to forming alloys that include at
least an equivalent atomic proportion of first metal (MI) to second
metal (M2). More particularly, in various embodiments there is a
preference for selecting first and second metal combinations that
provide bimetallic alloys of first and second metal,m m
-1x-2yr where
the atomic ratio of x:y is greater than or equal to 1. Further in
accordance with these and various other preferred embodiments, the
metal particles include bimetallic alloys in which the atomic
ratio of x:y is greater than about 2, or greater than about 3.
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For example, in the case of copper and platinum first and second
metals, respectively, the metal particles at the surface of the
support may include CuPt and/or Cu3Pt bimetallic alloys. By way of
further example, in the case of tin and platinum first and second
metals, respectively, at least some of the metal particles may
include Pt2Sn3, PtSn2, and/or PtSn4 bimetallic alloys. In the case
of iron and platinum first and second metals, respectively, the
metal particles at the surface of the support may include, for
example, Fe3Pt, FePt, Fe0.25Pt0.25.
[00192] Additionally or alternatively, it is also currently
believed that at least some of the supported metal particles
produced upon calcination of a catalyst precursor structure
prepared by displacement deposition of a noble (i.e., second)
metal as detailed herein include a relatively thin layer or shell
comprising second metal atoms (e.g., a layer of second metal atoms
no more than about 3 atoms thick) at least partially surrounding a
core comprising the first metal. The core generally comprises a
relatively high concentration of first metal (e.g., greater than
about 50 atom percent). The combination of a first metal-rich
core and second metal-containing shell provides a relatively low
proportion of unexposed second metal and, thus, provides
improvements in exposed metal surface area per unit metal weight.
It is currently believed that particles exhibiting such a core-
shell arrangement may generally provide a greater improvement in
second metal utilization over conventional supported noble metal
catalysts as compared to particles generally characterized as
first metal-rich (i.e., a greater increase in exposed second metal
surface area per unit second metal weight). Thus, as the fraction
of core-shell particles at the surface of the support increases,
metal utilization in the catalyst likewise increases.
Accordingly, in various preferred embodiments, the catalyst
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includes a predominant fraction of metal particles exhibiting a
core-shell arrangement. However, it is to be noted that
improvements in metal utilization are nonetheless provided by
virtue of the presence of metal particles generally rich in first
metal content, regardless of the presence of any particles
characterized as exhibiting a core-shell arrangement.
[00193] It is to be noted that reference to a porous substrate
such as a carbon support having first and second metals deposited
thereon (i.e., a first and second metal-containing support) as a
catalyst precursor structure does not exclude catalytic activity
of these impregnated supports in the absence of subsequent heat
treatment. In fact, experimental evidence indicates that metal-
impregnated supports prepared in this manner may function as
effective catalysts. Accordingly, elsewhere herein (including the
claims) porous substrates having a first metal deposited thereon
(e.g., a first metal-impregnated support) are likewise referred to
as catalyst precursor structures. But in various preferred
embodiments, the first and second metal-impregnated support is
heated at elevated temperatures to provide the catalyst (sometimes
referred to herein as a finished catalyst).
[00194] Experimental evidence indicates that catalysts (i.e.,
both catalyst precursor structures and finished catalysts)
prepared as detailed herein utilizing a noble metal and a first,
sacrificial metal layer are at least as active as conventional
noble metal on carbon catalysts on a per unit metal weight basis.
Without being bound to a particular theory, it is currently
believed that active sites or domains of second metal provided by
the method of the present invention provide an increase in
catalytic surface area per unit metal weight as compared to
conventional metal-containing catalysts prepared by methods that
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do not include displacement deposition of the second metal onto
one or more regions of a first, sacrificial metal.
[00195] Conventional noble metal on carbon catalysts generally
include noble metal-containing particles at the surface of the
support formed by agglomeration and/or sintering of noble metal
atoms and/or noble metal-containing particles. This agglomeration
typically occurs during post-deposition heat treatment of a noble
metal-impregnated support at relatively high temperatures. Metal
particles of conventional noble metal catalysts formed by
agglomeration of deposited metal at the surface of a support,
typically include the noble metal distributed throughout the
entire particle (e.g., the particles exhibit a composition profile
of relatively constant noble metal concentration throughout).
Particle stability (e.g., resistance to leaching and/or
deactivation under reaction conditions) generally increases with
increased particle size, but exposed metal catalytic surface area
per unit metal weight typically decreases in larger particles.
Thus, despite the increased stability, an abundance of relatively
large noble metal-containing particles and the attendant lower
catalytic metal surface area per unit metal weight represents less
efficient metal usage. Advantageously, first metal-rich particles
and/or metal particles comprising a noble (i.e., second) metal-
containing shell and first metal-containing core prepared in
accordance with various embodiments of the present invention
generally represent more efficient metal usage. For example, as
noted, the first metal-rich particles are believed to include the
second metal in a form (e.g., a bimetallic alloy including an
atomic excess of first metal) that provides a reduced proportion
of unexposed second metal.
[00196] Additionally or alternatively, and as detailed
elsewhere herein, larger, more stable metal particles in
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accordance with the present invention are not associated with an
unacceptable decrease in effective catalytic second metal surface
area since an increase in particle size is generally associated
with an increase in the size of the first metal-rich core. For
example, experimental evidence indicates relatively constant
thickness of the second metal-containing shell over a range of
particle sizes. Accordingly, as particle size increases, the
fraction (atom and/or weight) of the particle provided by the
first metal-rich core generally increases while the fraction of
the particle provided by the second metal-containing shell
generally decreases. However, the exposed second metal surface
area increases with increased particle size. For example, as
compared to a particle including a core 1 nm in diameter, at
constant second metal shell thickness, a particle including a core
nm in diameter may provide up to a 100-fold increase in exposed
surface area of the second metal-containing shell.
[00197] One mechanism for deactivation of conventional noble
metal on carbon catalysts prepared by deposition of noble metal in
the absence of a sacrificial metal involves over-oxidation of
platinum as a result of charge build-up among the active sites
comprising particles of agglomerated noble metal atoms. It is
currently believed that metal-containing particles in which a
second metal-containing shell at least partially surrounds a first
metal-containing core result in reduced over-oxidation of the
catalyst. In this manner, the form of the catalyst provides an
improvement in activity. With regard to a catalyst precursor
structure, it is currently believed that preferential deposition
of second metal by displacement of first metal to form domains or
active sites less prone to agglomeration to form metal-containing
particles than metal deposited in the absence of a sacrificial
metal provides greater dispersion of charge among the active sites
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and, thus, reduced catalyst deactivation by over-oxidation of the
metal.
[00198] It is to be noted that a certain degree of
agglomeration of second metal to form primarily second metal-
containing particles may occur in first and second metal-
containing catalysts prepared in accordance with the present
invention. However, it is currently believed that any such
agglomeration occurs to a lesser extent than observed in catalysts
prepared without a first, sacrificial metal and, in any event,
second metal agglomeration is not believed to occur to any
significant degree that prevents achieving the above-noted
benefits of improved metal utilization.
[00199] It is also currently believed that the above-described
methods utilizing a first, sacrificial metal layer may be utilized
in conjunction with the methods for treating porous substrates
detailed elsewhere herein. For example, a first metal may be
deposited onto a porous support first treated in accordance with
the methods detailed herein (e.g., a substrate having a pore
blocking compound disposed and/or preferentially retained within
its micropores), followed by deposition of a second metal onto one
or more regions of the deposited first metal. In this manner, it
is currently believed that deposition of both the one or more
regions of the first metal, and subsequent deposition of the
second metal thereon are preferentially directed outside the
relatively small pore (e.g., micropore) domain of the substrate,
thereby providing advantageous dispersion of the first and second
metals and contributing to one or more of the above-noted benefits
with respect to metal utilization.
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A. First Metal
[00200] In those embodiments of the present invention in which
the catalyst or precursor includes one or more regions of a first
metal at the surface of the support, the first metal is generally
selected from the group consisting of vanadium, tungsten,
molybdenum, gold, osmium, iridium, tantalum, palladium, ruthenium,
antimony, bismuth, arsenic, mercury, silver, copper, titanium,
tin, lead, germanium, zirconium, cerium, nickel, cobalt, iron,
chromium, zinc, manganese, aluminum, beryllium, magnesium,
lithium, barium, cesium, and combinations thereof. In various
preferred embodiments, the first metal is selected from the group
consisting of copper, iron, tin, nickel, cobalt, and combinations
thereof. In various other preferred embodiments, the first metal
comprises copper, tin, nickel, or a combination thereof. In
various other preferred embodiments, the first metal is tin or the
first metal is copper. In still further embodiments, the first
metal comprises cobalt, copper, iron and combinations thereof. In
various preferred embodiments, the first metal is copper. In
various other preferred embodiments, the first metal is iron. In
still further preferred embodiments, the first metal is cobalt.
[00201] Generally, the support is contacted with a deposition
bath comprising ions of the first metal and one or more other
components to deposit the first metal at the surface of the
support. At least two events occur during deposition of the first
metal at the surface of the support: (1) nucleation (i.e.,
deposition of first metal atoms at the surface of the support) and
(2) particle growth (i.e., agglomeration of deposited first metal
atoms). As used herein, the term region(s) of first metal refers
to a group of agglomerated first metal atoms at the surface of the
support. It is currently believed that the sizes, or dimensions of
these regions (i.e., the proportion of support surface area over
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which a region of first metal is deposited) may directly impact
the effectiveness/suitability of the catalyst.
[00202] For example, the proportion of deposition, or exchange
sites for second metal deposition decreases along with decreasing
dimensions of first metal regions. In addition, resistance to
leaching and/or deactivation under reaction conditions generally
decreases as one or more dimensions of the first metal region size
decrease. Thus, it is preferred that the dimensions of the first
metal regions are sufficiently resistant to metal leaching and
provide a sufficient proportion of sites for second metal
deposition. Accordingly, one or more conditions of first metal
deposition are preferably controlled to provide a suitable balance
between nucleation and agglomeration (i.e., particle growth) and,
thus, provide first metal regions of suitable dimensions that
provide sufficient exchange sites for deposition of second metal,
are stable themselves and, thus, promote deposition of stable
domains, or regions of second metal. For example, as detailed
elsewhere herein, first and second metal-containing supports
preferably include an excess of first metal, which contributes to
providing the second metal in a form that promotes more efficient
metal utilization.
[00203] In addition to achieving a desirable balance between
nucleation and agglomeration, the location, or dispersion of the
one or more regions of first metal at the support surface may
impact metal utilization. That is, the considerations noted above
generally concerning deposition of metal among relatively small
pores generally likewise apply to deposition of one or more first
metal regions and the dispersion of these regions among the pores
of porous substrates is currently believed to affect catalyst
performance. Accordingly, one or more conditions of first metal
deposition are generally controlled and/or selected to provide a
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desired dispersion of first metal regions. Thus, generally,
conditions of first metal deposition preferably promote deposition
of the first metal at the support surface to provide regions of
first metal at the support having one or more dimensions that
provide a suitable proportion of exchange sites for deposition of
second metal at the surface of the first metal regions. More
particularly, it is currently believed that the dimensions of the
first metal regions preferably provide a suitable excess of
deposited first metal with respect to the desired proportion of
second metal to be deposited. For example, as detailed elsewhere
herein, supports having first and second metals deposited thereon
in accordance with the present invention may be characterized by a
minimum atom ratio of first metal to second metal.
1. Coordinating Agents / Pore Blocking
[00204] In various preferred embodiments, preferential
deposition of the first metal outside relatively small pores
(e.g., the micropore domain) of the substrate may be promoted by
the presence of one or more components of the first metal
deposition bath. More particularly, dispersion of first metal in
this manner may be promoted by the presence of one or more
components of the deposition bath referred to herein as
coordinating agent (s)
[00205] It is currently believed that a component of the first
metal deposition bath may function as a coordinating agent by
forming one or more coordination bonds with the first metal and
that the thus formed coordination compound may be unable to enter
certain relatively small pores of the substrate, thereby
preventing coordinated first metal from depositing among those
portions of the substrate surface. It is to be understood that
the precise form of any coordination bond(s) between the compound
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and metal, or the precise form of any coordination compound thus
formed are not narrowly critical. However, it is currently
believed that a coordination compound generally includes an
association or bond between the first metal ion and one or more
binding sites of one or more ligands. The coordination number of
a metal ion of a coordination compound generally corresponds to
the number of other ligand atoms linked thereto. Ligands may be
attached to the central metal ion by one or more coordinate
covalent bonds in which the electrons involved in the covalent
bonds are provided by the ligands (i.e., the central metal ion can
be regarded as an electron acceptor and the ligand can be regarded
as an electron donor). The typical donor atoms of the ligand
include, for example, oxygen, nitrogen, and sulfur. The ligands
can provide one or more potential binding sites; ligands offering
two, three, four, etc., potential binding sites are termed
bidendate, tridendate, tetradentate, etc., respectively. Just as
one central atom can coordinate with more than one ligand, a
ligand with multiple donor atoms can bind with more than one
central atom. Coordinating compounds including a metal ion bonded
to two or more binding sites of a particular ligand are typically
referred to as chelates.
[00206] Additionally or alternatively, a coordinating agent as
described herein may promote dispersion of the first metal at the
support surface by virtue of the coordination bonds between the
coordinating agent and metal to be deposited retarding or delaying
reduction of the metal ions and metal deposition at the support
surface while promoting dispersion of the first metal over the
support surface. The strength of coordination between the
coordinating agent and metal generally influences the
effectiveness of the agent for promoting dispersion of the first
metal over the support surface. Unless the strength of
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coordination reaches a minimum threshold, the effect of the agent
on dispersion will not be noticeable to any significant degree and
the degree of coordination that prevails in the deposition bath
will essentially mimic water solvation. As the strength of
coordination between the agent and metal increases, a greater
concentration of reducing agent may be utilized and/or a
relatively strong reducing agent (e.g., metal hydride) may be
included in the deposition bath to promote reduction of the
coordination complex and/or first metal reduction and deposition.
Coordinating agent and/or ligand(s) derived therefrom present in
the deposition bath may effectively function as a pore blocking
compound during and/or after first metal deposition. For example,
once the coordination bond(s) between the first metal and the
coordinating agent have been broken, the agent or ligand(s) may be
disposed within micropores of the support.
[00207] In accordance with the foregoing regarding deposition
bath components that may function as coordinating agents, in these
and various other preferred embodiments, such components of the
first metal deposition bath may promote desirable dispersion of
the one or more regions of first metal by virtue of a pore
blocking function. That is, in addition to preventing entry of
coordinated first metal into certain pores of the substrate,
components of the first metal deposition bath described as
coordinating agents may themselves be deposited among certain,
relatively small pores of the porous substrate, thereby
inhibiting, and preferably substantially preventing, deposition of
first metal within the relatively small pores. Generally, these
compounds are believed to function as pore blocking compounds
during first metal deposition and that preferential deposition of
first metal and pore blocking may occur substantially
simultaneously to provide a first metal-impregnated substrate.
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[00208] But it is to be understood that treating a porous
substrate in accordance with the methods detailed above to dispose
within and/or introduce a pore blocking compound into pores of the
substrate, followed by metal deposition, likewise provides
suitable substrates.
[00209] A variety of compounds that function as coordinating
agents and/or pore blocking compounds may be included in the first
metal deposition bath to provide one or more of the above-noted
effects. Generally, these compounds are selected from the group
consisting of various sugars, 5- or 6-member ring-containing
compounds (e.g., 1,3- and 1,4-disubstituted cyclohexanes),
polyols, Rochelle salts, acids, amines, citrates, and combinations
thereof. For example, the compound may be selected from the group
consisting of sucrose, sorbitol, mannitol, xylitol, Rochelle salts
(potassium sodium tartrates), ethylenediaminetetraacetic acid
(EDTA), N-hydroxyethylethylenediaminetetraacetic acid (HEDTA),
nitrilotriacetic acid (NIA), N,N,N',N'- tetrakis(2-
hydroxypropyl)ethylenediamine, and combinations thereof.
[00210] It is to be noted that the advantageous effects
provided by the presence of these compounds referred to herein as
coordinating agents or pore blockers are based in part on
experimental evidence. While it is currently believed that one or
more of these compounds provide either or both of the coordinating
and pore blocking functions, it should be understood that the
present invention is not dependent on either or both of these
theories and does not require one or more compounds providing
either or both of these functions.
[00211] In various preferred embodiments (e.g., those in which
the first metal is copper or iron), the deposition bath comprises
sucrose that is believed to function as a coordinating agent
and/or pore blocking compound. In addition to these effect(s) in
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accordance with the preceding discussion, its presence may offer
other advantages. For example, as detailed elsewhere herein,
first metal deposition may proceed more readily at higher pH. The
coordinating effect of sucrose allows for deposition of the first
metal at higher pH since the coordinating effect reduces the risk
of excessive first metal precipitation at higher pH.
[00212] Generally, the coordinating agent/pore blocker, or a
combination of agents/blockers, is present in the first metal
deposition bath at a concentration of at least about 10 g/L, at
least about 20 g/L, or at least about 30 g/L. Preferably, this
component of the first metal deposition bath is present at a
concentration of from about 10 g/L to about 115 g/L, from about 25
g/L to about 100 g/L, or from about 40 g/L to about 85 g/L.
Further in accordance with these and various other preferred
embodiments, the weight ratio of coordinating agent to first metal
in the deposition bath is generally at least about 3:1, typically
at least about 5:1 and, more typically, at least about 8:1. For
example, generally the weight ratio of coordinating agent to first
metal in the deposition bath is generally from about 3:1 to about
20:1, typically from about 5:1 to about 15:1 and, more typically,
from about 8:1 to about 12:1.
2. Electroless Plating of First Metal
[00213] Generally and in accordance with the foregoing,
deposition of first metal at the surface of the support may be
conducted in accordance with conventional methods known in the
art. Thus, typically first metal deposition is conducted by
electroless plating in which the support is contacted with a
deposition bath generally comprising a source of the first metal
in the absence of an externally applied voltage. The deposition
bath generally comprises a reducing agent that reduces ions of the
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first metal to form metal atoms that are deposited at the surface
of the support.
[00214] Generally, the source of the first metal is a first
metal salt including, for example, first metal sulfates, first
metal nitrates, first metal chlorides, first metal tartrates,
first metal phosphates, and combinations thereof. The
concentration of first metal in the deposition bath is generally
selected in view of the desired first metal content. Typically,
the source of first metal is present in the deposition bath at a
concentration of at least about 0.25 g/L, at least about 1 g/L, at
least about 2.5 g/L, or at least about 4 g/L. For example, the
first metal source may be present in the deposition bath at a
concentration of from about 1 to about 20 g/L, from about 2.5 to
about 12.5 g/L, or from about 4 to about 10 g/L.
3. Copper Deposition
[00215] The following discussion focuses on deposition of
copper as the first metal onto a porous carbon support. However,
as detailed elsewhere herein, it should be understood that the
present invention likewise contemplates deposition of first metals
other than copper onto carbon supports, and deposition of copper
and other first metals onto non-carbon supports.
(a) Sources of Copper
[00216] Sources of copper ions suitable for use in the methods
of the present invention include copper salts such as the nitrate,
sulfate, chloride, acetate, oxalate, and formate salts of copper,
and combinations thereof. Salts containing copper in the divalent
state (i.e., Cu(II)) are generally preferred including, for
example, copper sulfate.
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(b) Copper Loading in Deposition Bath
[00217] First metal loading in the deposition bath may affect
the quality (e.g., resistance to leaching) and/or suitability
(e.g., dispersion of first metal over a sufficient portion of
support surface) of first metal deposition. More particularly,
the relative proportions of first metal and support are currently
believed to impact first metal deposition. Agglomeration, or
particle growth, and the dimensions of the resulting regions of
first metal may increase with increased copper loading. As noted
above, the dimensions of the first metal regions are preferably
controlled to promote a suitable balance between dispersion and
stability of the first and second metals. Accordingly, the
concentration of copper in the deposition bath satisfies the
above-noted limits and/or is within the above-noted ranges.
[00218] For example, typically copper is present in the first
metal deposition bath at a concentration of at least about 0.25
g/L, more typically at least about 1 g/L, still more typically at
least about 2 g/L, and even more typically at least about 3 g/L
(e.g., at least about 5 g/L). Preferably, copper is present in
the first metal deposition bath at a concentration of from about
0.25 to about 15 g/L, more preferably from about 1 to about 12 g/L
and, still more preferably, from about 2 to about 10 g/L.
(c) Reducing Agents
[00219] Suitable reducing agents include those generally known
in the art including, for example, sodium hypophosphite (NaH2P02),
formaldehyde (CH20) and other aldehydes, formic acid (HCOOH), salts
of formic acid, salts of borohydride (e.g., sodium borohydride
(NaBH4)), salts of substituted borohydrides (e.g., sodium
triacetoxyborohydride (Na(CH3CO2)3BH)), sodium alkoxides, hydrazine
(H2NNH2), and ethylene glycol. In various preferred embodiments,
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formaldehyde is the preferred reducing agent. For copper
deposition in non-aqueous deposition baths, gaseous hydrogen is
often the preferred reducing agent since it is generally readily
soluble in organic solvents.
[00220] The manner of addition of reducing agent to the
deposition bath is not narrowly critical, but in various
embodiments the reducing agent is added at a relatively slow rate
(e.g., over a period of from about 5 minutes to 3 hours, or over a
period of from about 15 minutes to about 1 hour) to a slurry of
the support and first metal in water or an alcohol and under an
inert atmosphere (e.g., N2). If the reducing agent is instead
first added to the copper salt, it preferably may be added to a
solution which contains the copper salt and also a coordinating
agent (e.g., chelator). The presence of the chelator inhibits the
reduction of the copper ions before the copper-salt solution is
combined with the support and which, as detailed herein, may
likewise promote advantageous deposition of first metal throughout
the surface of the support.
[00221] Typically, in the case of formaldehyde as the reducing
agent, the reducing agent is present in the first metal deposition
bath at a concentration of at least about 1 g/L, more typically at
least about 2 g/L and, still more typically, at least about 5 g/L.
For example, in the case of formaldehyde as the reducing agent,
preferably formaldehyde is present in the deposition bath at a
concentration of from about 1 to about 20 g/L, more preferably
from about 2 to about 15 g/L and, still more preferably, from
about 5 to about 10 g/L.
[00222] Additionally or alternatively, in the case of a
formaldehyde reducing agent, generally formaldehyde and the first
metal (e.g., copper) are present in the deposition bath at a
weight ratio of formaldehyde to first metal of at least about
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0.5:1, and typically at least about 1:1. For example, in various
embodiments, the weight ratio of formaldehyde to first metal in
the deposition bath is from about 0.5:1 to about 5:1, from about
1:1 to about 3:1, or from about 1:1 to about 2:1.
(d) Temperature
[00223] The temperature of the deposition bath may affect
nucleation and agglomeration (e.g., particle growth) that occur
during first metal deposition. For example, generally nucleation
(i.e., metal deposition) and agglomeration increase with
increasing deposition bath temperature.
[00224] Thus, preferably the temperature of the deposition
bath does not reach a level that promotes metal agglomeration
and/or metal leaching under reaction conditions to an undesired
degree. Reducing the temperature of the plating bath generally
suppresses nucleation to a greater degree than agglomeration.
Accordingly, the temperature of the plating bath is preferably
high enough so that nucleation is not retarded to an unacceptable
degree. In accordance with the present invention, it is currently
believed that first metal deposition baths having a temperature of
from about 5 C to about 60 C generally address these concerns and
provide suitable deposition of the first metal. Preferably, the
temperature of the first metal deposition bath is from about 10 C
to about 50 C; more preferably, the temperature of the first metal
deposition bath is from about 20 C to about 45 C. It is to be
noted that reference to the temperature of the first metal
deposition bath may refer to the temperature of the bath prior to
and/or during contact of the deposition bath and the support.
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(e) Agitation
[00225] Preferably the first metal deposition bath is agitated
to promote dispersion of the first metal over the surface of the
support. Agitation may also promote diffusion of the reducing
agent throughout the support. Experimental evidence indicates
that sufficient agitation may contribute to improvements in
catalytic activity. However, excessive agitation of the
deposition bath may cause dispersion of copper to a degree that
provides first metal regions that may be less resistant to
leaching than less dispersed regions. For example, undesirably
high dispersion may result in deposition of a portion of first
metal within the relatively small pores of the support that is
less prone to agglomeration to form first metal regions generally
resistant to leaching.
[00226] In addition, it is currently believed that the type of
agitator may impact deposition of the first metal. Experimental
evidence indicates that the first metal (e.g., copper) may deposit
onto the agitator surface resulting in reduced first metal
deposition onto the carbon support and, therefore, reduced sites
for deposition of second metal. For example, first metal may
deposit onto the surface of agitators that include or are
constructed of metal (e.g., coated metal agitators). Thus, in
various preferred embodiments, the agitator is constructed of
material that generally prevents, and preferably substantially
completely prevents first metal deposition at the surface of the
agitator. For example, the agitator may preferably be constructed
of glass, or various other materials that preferably avoid first
metal deposition at the agitator surface.
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(f) Deposition pH
[00227] Copper deposition is generally more effective at
higher pH (e.g., greater than about 8, greater than about 9, or
greater than about 10). In fact, as deposition bath pH increases,
copper deposition through reduction and precipitation onto the
support may proceed at a rate that may hinder sufficient
dispersion of the first metal over the support surface. In
addition to the above-noted benefits, the presence of a
coordinating agent such as sucrose is currently believed to retard
copper precipitation at high pH and thereby promote sufficient
dispersion of the metal over the surface of the support.
Formation of a coordination complex between the first metal and a
coordinating agent is generally enhanced at the above-noted pH
levels. However, at certain levels the pH of the deposition bath
may negatively impact solvation of first metal ions and first
metal reduction and deposition. Accordingly, in various preferred
embodiments in which a coordinating agent is present in the
deposition bath, the pH of the deposition bath is from about 8 to
about 13, or from about 9 to about 12.
4. Iron Deposition
[00228] In various preferred embodiments, the first metal is
iron. Generally, deposition of iron at the surface of the support
may be conducted in accordance with conventional methods known in
the art (e.g., electroless plating). Thus, typically iron
deposition is conducted by a process comprising contacting the
support with a deposition bath comprising a source of the first
metal in the absence of an externally applied voltage. For
example, iron may be deposited via electroless deposition using
methods generally known in the art including, for example, those
described in U.S. Patent No. 6,417,133 and by Wan et al. in
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International Publication No. WO 2006/031938. In various
embodiments, as detailed below, the deposition bath comprises a
reducing agent that reduces ions of the first metal that are
deposited at the surface of the support.
(a) Sources of Iron
[00229] Suitable sources of iron include iron salts such as
the nitrate, sulfate, chloride, acetate, oxalate, and formate
salts, and combinations thereof. In various preferred
embodiments, the source of iron comprises iron chloride (i.e.,
FeC13), iron sulfate (i.e., Fe2(504)3), or a combination thereof.
[00230] The concentration of iron source in the deposition
bath is not narrowly critical and is generally selected in view of
the desired metal content and/or the composition of the source.
Often, the source of iron is present in the deposition bath at a
concentration of at least about 5 g/L and more typically from
about 5 to about 20 g/L. In various embodiments, the entire
proportion of the source of iron is introduced into the deposition
bath prior to, during, or after addition of the carbon support to
the deposition bath and/or the vessel containing deposition bath.
Additionally or alternatively (including as described in the
working Examples), the source of iron may be metered, or pumped
into the deposition bath and/or a vessel containing the carbon
support. In this regard it is to be understood that metered
addition of the source of iron is controlled to provide deposition
of a suitable proportion of iron at the support surface,
regardless of the concentration of iron source in the deposition
bath at any point(s) during iron deposition.
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(b) Iron Loading in Deposition Bath
[00231] As with other first metals (e.g., copper as described
above), iron loading in the deposition bath may affect the quality
and/or dispersion of iron deposition over a sufficient portion of
the support surface. The concentration of iron in the deposition
bath is generally controlled to address these concerns and others
(e.g., agglomeration of first metal). For example, typically iron
is present in the first metal deposition bath at a concentration
of at least about 2 g/L, more typically at least about 3 g/L and,
still more typically, at least about 4 g/L. Preferably, iron is
present in the deposition bath at a concentration of from about 2
to about 8 g/L, more preferably from about 3 to about 6 g/L and,
still more preferably, from about 4 to about 5 g/L.
(c) Reducing Agents
[00232] To provide a driving force for deposition of a second
metal thereon, preferably iron is deposited in an at least
partially reduced state, e.g., as Fe+2 and/or its fully reduced
state as Fe . Thus, in various embodiments, the iron first metal
deposition bath comprises a reducing agent. Any reducing agent is
generally utilized under the conditions set forth above regarding
copper deposition (e.g., concentration of reducing agent, etc.).
Suitable reducing agents include sodium hypophosphite (NaH2P02),
formaldehyde (CH20), formic acid (HCOOH), salts of formic acid,
sodium borohydride (NaBH4), sodium triacetoxyborohydride
(Na(CH3002)3BH)), sodium alkoxides, hydrazine (H2NNH2), and ethylene
glycol. In view of the greater electropositivity of iron as
compared to copper, stronger reducing agents for iron first metal
deposition may be preferred as compared to those preferred for
copper first metal deposition. Thus, in various preferred
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embodiments the reducing agent is sodium borohydride or ethylene
glycol.
[00233] In those embodiments in which the reducing agent is
sodium borohydride and/or ethylene glycol, the molar ratio of
reducing agent to iron deposited is generally at least 1,
typically at least about 2, and more typically at least about 3.
Typically in accordance with these embodiments, the molar ratio of
sodium borohydride to iron deposited is form about 1 to about 5
and, more typically, from about 2 to about 4.
(d) Temperature
[00234] As with copper deposition, the temperature of the
deposition bath affects iron nucleation and agglomeration.
Generally, the temperature of the deposition bath is sufficient to
provide suitable nucleation and agglomeration, but preferably not
at a level that promotes first metal agglomeration to an undesired
degree. Generally, iron deposition bath temperatures ranging from
about 5 C to about 60 C may be utilized to provide suitable
catalysts. Often, the temperature of the iron deposition bath is
above ambient conditions in order to provide sufficient nucleation
and, more particularly, suitable dispersion of first metal over
the support surface. Thus, typically the temperature of the iron
deposition bath is from about 25 C to about 60 C and, more
typically, from about 25 C to about 45 C.
(e) Agitation
[00235] The iron first metal deposition bath is typically
agitated to promote dispersion of iron over the surface of the
support. As in copper deposition, agitation may also promote
diffusion of the reducing agent throughout the support. Any
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agitation during first metal deposition is generally conducted in
accordance with the above description regarding copper deposition.
(f) Deposition pH
[00236] As with copper deposition, iron deposition generally
proceeds more readily as deposition pH increases. Thus, typically
the iron deposition pH is at least about 8, at least about 9, or
at least about 10. Also as with iron deposition, the presence of
a coordinating agent (e.g., sucrose) is currently believed to
retard iron precipitation at high pH and thereby promote
sufficient dispersion of the metal over the surface of the
support. As noted, formation of a coordination complex between
the first metal and a coordinating agent is generally enhanced at
the above-noted pH levels. But at certain pH levels, deposition
bath pH may negatively impact solvation or iron ions and first
metal reduction and deposition. Thus, in various preferred
embodiments the pH of the iron deposition bath is from about 8 to
about 13, or from about 9 to about 12.
5. First Metal Deposition Atmosphere
[00237] Regardless of the precise conditions of first metal
deposition and the dispersion of first metal deposited at the
support surface, oxidation of deposited first metal may reduce the
proportion of first metal exchange sites available for second
metal deposition. Accordingly, in various preferred embodiments,
the first metal is deposited onto the support in the presence of a
non-oxidizing environment (e.g., a nitrogen atmosphere).
Additionally or alternatively, water and/or other deposition bath
components are degassed to remove dissolved oxygen using methods
known to those skilled in the art.
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B. Second Metal
[00238] Conventional noble metal-containing catalysts are
generally prepared by depositing a noble metal at the surface of a
support, typically a porous carbon support. Agglomeration of
noble metal into particles, thereby reducing exposed metal
catalytic surface area, has been observed with these methods. In
particular, an abundance of relatively large metal-containing
particles may represent inefficient usage of the metal by virtue
of these particles providing a relatively low exposed catalytic
surface area per unit metal.
[00239] In accordance with various embodiments of the present
invention, noble metal-containing catalysts are prepared by a
method in which the noble metal is deposited in a manner that
increases the exposed metal catalytic surface area per unit weight
of metal. More particularly, the noble metal is deposited at the
surface of one or more regions of first metal by displacement of
first metal from the regions. It is currently believed that
deposition of the noble metal utilizing a first, sacrificial metal
results in reduced noble metal agglomeration. For example, as
noted elsewhere herein, deposition of the noble metal in this
manner provides a catalyst precursor structure in which the noble
metal deposited at the surface of one or more regions of a first
metal is less prone to agglomeration than noble metal deposited
directly onto the surface of a porous support. It is further
currently believed that, upon heat treatment of supports having
thereon noble metal deposited in this manner, metal particles are
formed that provide improved noble (second) metal utilization
(e.g., greater exposed metal catalytic surface area per unit metal
weight).
[00240] Generally, the second metal is deposited onto a first
metal-impregnated support by contact of the metal-impregnated
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support and a second metal deposition bath. More particularly,
the second metal is generally deposited via electroless deposition
in which the first metal-impregnated support and second metal
deposition bath are contacted in the absence of an externally
applied voltage.
[00241] As noted, in various embodiments, the second metal is
a noble metal. Typically, the noble metal is selected from the
group consisting of platinum, palladium, ruthenium, rhodium,
iridium, silver, osmium, gold, and combinations thereof. In
various preferred embodiments, the noble metal comprises platinum.
In still other preferred embodiments, the noble metal comprises
more than one metal (e.g., platinum and palladium or platinum and
gold).
[00242] The following discussion focuses on deposition of
platinum as the second metal, but it is to be understood that the
present invention likewise contemplates utilizing any or all of
the above-noted noble metals as the second metal. In addition,
suitability of a combination of metals for use in displacement
deposition of a second metal onto one or more regions of a first
metal generally depends on their relative electropositivities.
Thus, the present invention is not limited to deposition of noble
metals as the second metal. For example, two metals designated as
candidate first metals elsewhere herein may provide the first and
second metals so long as their relative electropositivities allow
displacement deposition of the second metal onto one or more
regions of the first metal.
[00243] Suitable sources of platinum include those generally
known in the art for use in liquid phase deposition of platinum
and include, for example, H2P tC1 4 f H 2P tC1 6 f K2P tC1 4 f N a 2P tC1 6 f
and
combinations thereof. Thus, in various embodiments, the second
metal deposition bath comprises a source of platinum including a
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platinum salt comprising platinum at an oxidation state of +2
and/or +4. As noted, in various preferred embodiments, the source
of platinum provides platinum ions exhibiting an oxidation state
of +2. However, it is to be understood that effective catalysts
may be prepared utilizing sources of platinum that provide
platinum ions having other oxidation states (e.g., +4), and
sources of platinum that provide platinum ions that comprise
platinum ions exhibiting oxidation states other than +2.
Similarly, sources of noble metals other than platinum and second
metal sources generally that provide metal ions at lower oxidation
states are likewise preferred. For example, it is currently
believed that palladium provided by Na2PdC14 and PdC12 may be
utilized to prepare active catalyst comprising palladium as the
second metal.
[00244] Generally, the source of platinum is present in the
second metal deposition bath in a proportion that provides a molar
concentration of second metal ions less than the concentration of
first metal ions in the first metal deposition bath. Typically,
the molar ratio of copper ions in the first metal deposition bath
to noble metal ions in the second metal deposition bath is greater
than 1, more typically at least about 2 and, even more typically
at least about 3 (e.g., at least about 5). In various preferred
embodiments, the molar ratio of copper ions in the first metal
deposition bath to noble metal ions in the second noble metal
deposition bath is typically greater than 1 to about 20, more
typically from about 2 to about 15, still more typically from
about 3 to about 10 and, even more typically, from about 5 to
about 7.5.
[00245] Generally, the first metal-impregnated support is not
subjected to elevated temperatures prior to contact with the
second metal deposition bath. That is, the catalyst precursor
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structure is preferably not subjected to temperatures that would
promote formation of metal-containing particles (e.g., through
agglomeration of first metal particles). For example, the first
and second metal-impregnated support is generally subjected to
temperatures of no more than about 200 C, no more than about 150 C,
and preferably no more than about 120 C prior to contact with the
second metal deposition bath.
[00246] Typically, the metal-impregnated support and second
metal deposition bath are contacted at a temperature of at least
about 5 C, typically at least about 10 C and, more typically, at
least about 15 C. Preferably, the first metal-impregnated support
and the second metal deposition bath are contacted at a
temperature of from about 10 C to about 60 C, from about 20 C to
about 50 C, or from about 25 C to about 45 C.
[00247] Often, the second metal deposition bath has a pH less
than the pH of the first metal deposition bath and is from about
1 to about 12 or from about 1.5 to about 10. In accordance with
various embodiments, the pH of the deposition bath is from about 2
to about 7 or from about 3 to about 5. Such pH conditions have
been observed to be suitable for deposition of a noble (second)
metal onto one or more regions of copper first metal. In various
preferred embodiments, the first metal is iron. As compared to
copper, iron may be more readily leached from the surface of the
support as the pH of the deposition bath decreases. Thus, in
accordance with those embodiments in which the first metal is
iron, the pH of the noble (second) metal deposition bath is
typically from about 4 to about 9, and preferably from about 5 to
about 8 (e.g., about 7).
[00248] As noted above, preferably the first metal is
deposited in an environment that avoids oxidation of deposited
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first metal that may reduce the proportion of first metal exchange
sites available for second metal deposition. Likewise, in various
preferred embodiments, the second metal is also deposited onto the
first metal-impregnated support in a non-oxidizing environment
(e.g., a nitrogen atmosphere) to avoid oxidation of deposited
first and second metal.
C. First and Second Metal-Impregnated Support
[00249] As noted, preferably the first metal deposited at the
support surface provides suitable exchange sites for deposition of
second metal at the surface of one or more regions of first metal
and, more particularly, an excess of exchange sites for second
metal deposition. Accordingly, typically the atom ratio of first
metal to second metal of the first and second metal-impregnated
support (i.e., catalyst precursor structure) is at least about
1.5, more typically at least about 2 and, still more typically, at
least about 3 (e.g., at least about 4 or at least about 5).
Preferably, the atom ratio of first metal to second metal of the
first and second metal-impregnated support is from about 1.5 to
about 15 more preferably from about 2 to about 15, still more
preferably from about 3 to about 10 and, even more preferably,
from about 4 to about 8.
[00250] As noted, heat treatment of the impregnated support
provides first and noble (second) metal-containing particles at
the support surface including the noble (second) metal in a form
that provides advantageous metal utilization. An excess of first
metal atoms to second metal atoms on the impregnated support is
believed to result in formation of such particles. For example,
the excess of first metal to second metal atoms on the impregnated
support provides first metal-rich particles that include a
relatively low proportion of unexposed noble (second) metal
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throughout the particles (e.g., a bimetallic alloy having an
excess of first metal atoms).
[00251] Additionally or alternatively, and as generally
depicted in Fig. 2, heat treatment of the first and second metal-
impregnated support may form metal particles comprising a core and
a shell at least partially surrounding the core. It is currently
believed that the composition of the core and shell indicate
improvements in metal utilization and, more particularly,
improvements in second metal (e.g., noble metal) utilization. For
example, the core of these particles is generally first metal-
rich, thereby providing a relatively low proportion of unexposed
second metal throughout the particles.
[00252] As the atom ratio of first metal to second metal in
the catalyst precursor increases, the extent to which the first
metal-rich core is surrounded by a second metal-containing shell
may decrease. For example, a relatively high excess of first
metal exchange sites for second metal deposition may result in a
portion of exchange sites that do not participate in displacement
deposition of noble (second) metal. Such particles may be
prepared from catalyst precursors in which the atom ratio is near
or above the above-noted upper limit of first metal to second
metal atom ratios (e.g., about 10 or higher). Although less
preferred, it should be understood that a decrease in the degree
to which the core is surrounded by a second metal-containing shell
does not necessarily indicate a lack of improved second metal
utilization. These particles may nonetheless provide improved
metal utilization based on, for example, a first metal-rich core
that provides a relatively low proportion of unexposed, and
potentially unutilized noble (second) metal. However, it is
currently believed that the structure of the particles may shift
toward increased coverage of the first metal-rich core by the
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second metal-containing shell. More particularly, this shift in
form of the particles may comprise leaching of first metal from
the metal particle at the support surface during use of the
catalyst in liquid phase reactions. Second metal may likewise be
removed or leached from the particles, but it is currently
believed that first metal is removed from the particles to a
greater degree than second metal. Accordingly, the atom ratio of
first metal to second metal approaches more preferred ranges and
it is currently believed that as a result of this removal the
structure of particles shifts to more preferred (i.e., more
extensive) coverage of the first metal-rich core by the second
metal-containing shell. After a period of use, the leaching of
first metal from the metal particles on the support surface
generally decreases. Following such a period of use, it is
currently believed that catalysts comprising particles having a
more preferred ratio of first metal to second metal atoms with the
attendant shift in structure, thereafter exhibit performance
characteristics comparable to catalysts prepared using the more
preferred ratios of first metal to second metal atoms. This
"self-correcting" behavior has been observed, for example, in
connection with catalysts in which the first metal is copper and
the second metal is platinum.
D. Heat Treatment of First and Second Metal-Impregnated
Supports
[00253] As noted, it is to be understood that the metal-
impregnated support of the present invention is a suitable
catalyst as described in the working examples detailed herein.
However, typically in accordance with various preferred
embodiments, the metal-impregnated support is treated at elevated
temperatures generally as detailed elsewhere herein (e.g., in the
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presence of a non-oxidizing environment at temperatures in excess
of about 800 C) to form a finished catalyst. Typically, the metal-
impregnated support is heated to temperatures from about 400 C to
about 1000 C, more typically from about 500 C to about 950 C, still
more typically from about 600 C to about 950 C and, even more
typically, from about 700 C to about 900 C. Subjecting metal-
impregnated supports to such temperatures provides finished
catalysts exhibiting reduced metal leaching and improved metal
utilization as detailed elsewhere herein (e.g., catalysts
comprising first metal-rich particles and/or particles including a
first metal-rich core at least partially surrounded by a second
metal-rich shell).
[00254] Stable metal particles (i.e., resistant to leaching)
are currently believed to be readily formed in the case of first
and second metal-impregnated supports in which the first metal is
iron and the second metal is platinum. Iron and platinum-
impregnated supports (i.e., iron-platinum catalyst precursors)
have been observed to exhibit suitable stability during reaction
testing. Preferably, however, the iron-platinum catalyst
precursor is subjected to elevated temperatures to prepare a
finished catalyst. It is currently believed that heating the
iron-platinum impregnated support improves activity. But, in view
of the advantageous stability of the iron and platinum-impregnated
supports, suitable catalysts may be prepared therefrom by heating
the catalyst precursor to temperatures within, but at or near the
lower limits of the above-noted ranges. Thus, in accordance with
certain embodiments, platinum-iron impregnated supports are
subjected to a maximum temperature of from about 400 C to about
750 C, or from about 500 C to about 650 C to prepare a finished
catalyst.
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[00255] As noted, the degree of first and second metal
alloying generally increases with increasing temperature to which
the metal-impregnated support is subjected. Accordingly,
subjecting the iron/platinum-impregnated support to a relatively
low maximum temperature is currently believed to provide a
relatively low degree of iron and platinum alloying. Although
catalysts of the present invention include the first and second
metals in a form that represents efficient metal utilization
(e.g., a first metal-rich alloy), alloy formation unavoidably
results in unexposed noble (second) metal. Thus, preparing iron
and platinum-containing catalysts by subjecting the metal-
impregnated support to relatively low temperature may contribute
to improved metal utilization. However, in this regard it is to
be noted that preparing iron and platinum-containing catalysts by
subjecting the supports to higher temperatures, e.g., in the
ranges noted above such as 700 C or higher, is likewise currently
believed to provide catalysts that represent more efficient metal
utilization.
E. Iron and Platinum Deposition Protocols
[00256] Suitable iron and platinum-containing catalysts
generally may be prepared in accordance with the above discussion
regarding iron (first metal) and platinum (second metal)
deposition, both in accordance with the above discussions
concerning first and second metals generally, and specifically
iron and platinum. However, in accordance with the present
invention it has been discovered that advantageous catalysts are
provided by combinations of particular features of iron (first
metal) and platinum (second metal) deposition.
[00257] For example, in various preferred embodiments, the
iron (first metal) deposition bath comprises ethylene glycol as a
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reducing agent, but does not comprise a separate coordinating
agent (e.g., sucrose). However, it is to be understood that the
ethylene glycol reducing agent may, in fact, function as a
coordinating agent to a certain degree.
[00258] In still other preferred embodiments, the iron
deposition bath comprises both a reducing agent and a coordinating
agent. In various such embodiments, ethylene glycol is the
reducing agent and sucrose is the coordinating agent. In further
such embodiments, ethylene glycol and sodium borohydride are
utilized as reducing agents for iron deposition, and the iron
deposition bath also comprises sucrose as a coordinating agent.
[00259] In various other preferred embodiments, the iron
(first metal) deposition bath comprises sodium borohydride as a
reducing agent generally in accordance with the above discussion.
The iron deposition bath does not comprise a separate coordinating
agent (e.g., sucrose).
F. First and Second Metal-Containing Catalysts
[00260] As noted, first and noble (second) metal-impregnated
supports typically contain an excess of first metal atoms over
second metal atoms. In accordance with these and various other
embodiments, generally the first metal constitutes at least about
1% by weight, at least about 1.5% by weight, or at least about 2%
by weight of the catalyst. Typically the first metal constitutes
at least about 3% by weight, at least about 4% by weight, or at
least about 5% by weight of the catalyst. For example, preferably
the first metal constitutes from about 3% to about 25% by weight
of the catalyst, more preferably from about 4% to about 20% by
weight of the catalyst and, still more preferably, from about 5%
to about 15% by weight of the catalyst. In various other
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embodiments (e.g., those in which iron is the first metal), the
first metal constitutes from about 1% to about 10% by weight, more
preferably from about 1.5% to about 8% by weight and, still more
preferably, from about 2% to about 5% (e.g., about 4%) by weight
of the catalyst.
[00261] In accordance with the foregoing, catalysts of various
embodiments of the present invention generally contain at least
about 1% by weight noble (second) metal, at least about 2% by
weight noble metal, or at least about 3% by weight noble metal.
Typically, the catalysts contain less than about 8% by weight
noble metal, more typically less than about 7% by weight noble
metal and, still more typically, less than about 6% by weight
noble metal. In accordance with various preferred embodiments,
the catalysts contain less than about 5% or less than about 4% by
weight noble metal (e.g., from about 1% to about 3% by weight
noble metal). Catalysts prepared as detailed herein more
efficiently utilize the noble (second) metal as compared to
conventional catalysts, thereby providing catalysts at least as
active or even more active than conventional noble metal-
containing catalysts. For example, catalysts can be prepared that
include metal loadings similar to conventional noble metal-
containing catalysts, but are generally more active and, in
various preferred embodiments, much more active than conventional
noble metal-containing catalysts. In this manner, catalytic
activity can be increased without an increase in noble metal
loading, which may be undesired due to processing limitations. In
various embodiments, active catalysts can be prepared that contain
from about 3% to about 6% by weight noble metal, or from about 4%
to about 5% by weight noble metal.
[00262] By way of further example, more efficient metal usage
by catalysts of the present invention allows preparation of
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catalysts that include a reduced proportion of second metal as
compared to conventional noble metal-containing catalysts, but
that are at least as active and, in various preferred embodiments,
more active than conventional noble metal-containing catalysts.
In this manner, catalysts of the present invention can provide
activities equivalent to those provided by conventional noble
metal-containing catalysts at lower noble metal loadings, or
greater catalytic activities at equivalent noble metal loadings.
For example, in various embodiments, active catalysts may be
prepared that contain from about 1% to about 5% by weight, from
about 1.5% to about 4% by weight, or from about 2% to about 3% by
weight noble metal.
[00263] In various embodiments, first metal to second metal
atom ratio in metal particles at the surface of the catalyst
support generally increases with increasing particle size. It is
currently believed that as particle size increases the portion of
the particle constituting the first metal-rich core increases,
while the portion (i.e., weight fraction) of the particles
constituting the second metal-containing shell decreases. As
previously noted, larger metal-containing particles are generally
more resistant to leaching from the surface of the catalyst
support. However, a significant fraction of larger particles is
generally undesired in conventional noble metal-containing
catalysts because as particle size increases the proportion of
noble metal distributed within the particle that does not
contribute to effective catalytic surface area increases. . Thus,
a relatively high proportion of large particles comprising a
second metal-rich shell in accordance with the present invention
provides improved stability, without the sacrifice in exposed
noble (second) metal catalytic surface area associated with
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relatively large particles in conventional noble metal-containing
catalysts.
[00264] For example, in various embodiments, the catalyst
includes metal-containing particles characterized by a particle
size, as determined using electron microscopy, such that a
significant fraction (e.g., at least about 80%, at least about
90%, or at least about 95%, number basis) of the particles are
from about 5 to about 60 nm, or from about 5 to about 40 nm in
their largest dimension. In addition, the thickness of the second
metal-containing shells of the particles within these size
distributions nm is typically less than about 3 nm, more typically
less than about 2 nm, and preferably less than about 1 nm (e.g.,
less than about 0.8 nm or less than about 0.6 nm).
[00265] Improvements in metal utilization may be characterized
by an increase in the proportion of exposed noble (second) metal
of the catalyst. More particularly, improvements in metal
utilization may be indicated by an increase in the surface area of
exposed noble metal per unit weight catalyst per unit weight noble
metal. The total exposed noble metal surface area of catalysts of
the present invention may be determined using static carbon
monoxide chemisorption analysis, including Protocol A described in
Example 67. The carbon monoxide chemisorption analysis described
in Example 67 includes first and second cycles. Catalysts of the
present invention subjected to such analysis are generally
characterized as chemisorbing at least about 500 moles of carbon
monoxide per gram catalyst per gram noble metal and, more
generally, at least about 600 moles of carbon monoxide per gram
catalyst per gram noble metal. Typically, catalysts of the
present invention are characterized as chemisorbing at least about
700, at least about 800, at least about 900, at least about 975,
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at least about 1000, or at least about 1100 moles of carbon
monoxide per gram catalyst per gram noble metal.
[00266] An alternative or additional indicator of efficient
metal utilization is the proportion of the noble (second) metal of
the catalyst that may be found within a shell at least partially
surrounding a first metal-rich core. Generally, at least about
10%, at least about 20%, at least about 30%, at least about 40%,
or at least about 50% of the noble metal is present within the
shell of the metal particles. Typically, at least about 60% and,
more typically, at least about 70% (e.g., at least about 80% or at
least about 90%) of the noble metal is present within the shell of
the metal particles.
[00267] Additionally or alternatively, efficient metal
utilization may be indicated by the proportion of noble (second)
metal at the surface of metal particles. That is, efficient metal
utilization may be indicated by the proportion of noble metal at
the surface of first metal-rich particles, e.g., second metal
present in an alloy and/or within a second metal-rich shell at
least partially surrounding a first metal-rich core. Generally,
the atom percent of noble metal at the surface of first and noble
(second) metal-containing particles is at least about 2%, or at
least about 5%. Typically, the atom percent of noble metal at the
surface of first and noble metal-containing particles is at least
about 10%, more typically at least about 20%, even more typically
at least about 30%, and preferably at least about 40% (e.g., at
least about 50%).
[00268] Energy dispersive x-ray spectroscopy (EDX) line scan
analysis results for catalysts of the present invention (e.g., as
described in Protocol B in Example 68) also indicate efficient
metal utilization. More particularly, line scan analysis results
for metal particles of catalysts of the present invention indicate
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a distribution of noble (second) metal in which a significant
fraction of the noble (second) metal is present within a shell at
least partially surrounding a first metal-rich core. Additionally
or alternatively, line scan analysis results for metal particles
of catalysts of the present invention indicate a noble metal
distribution in which a significant fraction of the noble metal is
disposed at or near the surface of a metal particle (s)
[00269] Efficient metal utilization in particles of catalysts
of the present invention is indicated by a second metal
distribution that produces an EDX line scan signal that does not
vary significantly over a scanning region. As used herein, the
term scanning region refers to the portion of the largest
dimension of the particle analyzed over which a relatively low
degree of variation in second metal signal indicates improved
metal utilization. A relatively constant second metal line scan
signal over a scanning region corresponding to a significant
portion of the largest dimension of the particle indicates that a
significant fraction of the second metal is distributed near the
surface of the particle rather than throughout the metal particle.
By contrast, the latter type of distribution would cause the
second metal signal to increase (decrease) significantly in that
portion of the scanning region where the probe is directed to a
thicker (thinner) dimension of the particle. For example, in
various embodiments, the second metal signal generated during EDX
line scan analysis of a particle at the surface of a catalyst in
accordance with the present invention varies by no more than about
25%, no more than about 20%, no more than about 15%, no more than
about 10%, or no more than about 5% across a scanning region that
is a least about 70% of the largest dimension of at least one
particle. In further embodiments, the second metal signal varies
by no more than about 20%, no more than about 15%, no more than
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about 10%, or no more than about 5% across a scanning region that
is at least about 60% of the largest dimension of at least one
particle. In still further embodiments, the second metal signal
varies by no more than about 15%, no more than about 10%, or no
more than about 5% across a scanning region that is at least about
50% of the largest dimension of at least one particle.
[00270] The particles having metal distributions characterized
by EDX line scan analysis as detailed above are typically first
metal-rich and, more particularly, typically include the second
metal and first metal at an atomic ratio of second metal to first
metal in a particle(s) analyzed of less than 1:1. Typically, the
second metal to first metal atomic ratio of the particle(s) is
less than about 0.8:1 and, more typically, less than about 0.6:1
(e.g., less than about 0.5:1).
[00271] Generally, the first and second metal particle(s) of
catalysts of the present invention having a second metal
distribution characterized by EDX line scan analysis indicating
efficient metal utilization have a largest dimension of at least
about 6 nm, typically at least about 8 nm, more typically at least
about 10 nm and, still more typically, at least about 12 nm.
[00272] The relative magnitudes of first and second metal
signals across the scanning region may also indicate first and
second metal distributions in a form that indicates efficient
metal utilization. More particularly, generally in accordance
with various embodiments, the ratio of the maximum first metal
signal to the maximum second metal signal across the scanning
region is at least about 1.5:1, at least about 2:1, or at least
about 2.5:1. Typically, the ratio of the maximum first metal
signal to the maximum second metal signal across the scanning
region is at least about 3:1, at least about 4:1, or at least
about 5:1.
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[00273] It is to be understood that efficient metal
utilization may be indicated by identification of at least one
particle at the surface of the catalyst support having a noble
(second) metal distribution characterized as described above.
That is, the population of metal particles at the surface of the
catalyst support may include both particles satisfying one or more
of the noble metal distribution characteristics and those that do
not. However, metal utilization is enhanced as the proportion of
metal particles exhibiting these preferred noble metal
distribution characteristics increases and typically a plurality
of metal particles will possess these characteristics. More
typically, the second metal distribution of each of a portion
(number basis) of the particles at the surface of the support
indicates efficient metal utilization. Generally, at least about
1%, at least about 5%, at least about 10%, at least about 15%, at
least about 20%, or at least about 25% of the metal particles
satisfy the second metal distribution characteristics. Typically,
at least about 30%, at least about 35%, at least about 40%, at
least about 45%, at least about 50%, at least about 55%, at least
about 60%, or at least about 65% of the metal particles satisfy
the second metal distribution characteristics. The proportion of
metal particles satisfying one or more of the noble metal
distribution characteristics is somewhat dependent upon the
particular first metal and second metal combination. For example,
catalysts prepared with copper and platinum as the first and
second metals, respectively, have been observed to produce
catalysts in which a large portion of metal particles at the
surface thereof possess these preferred noble metal distribution
characteristics. Accordingly, in these and other preferred
embodiments, at least about 70%, at least about 75%, at least
about 85%, or at least about 90% of the metal particles at the
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surface of the support satisfy one or more of the second metal
distribution characteristics determined by EDX line scan analysis.
[00274] As previously noted, in various embodiments of the
present invention (e.g., in which copper is the first metal and
platinum is the second metal) the second metal-rich shell may
provide relatively low coverage of the first metal-rich core and,
during subsequent use of the catalyst, the structure of the
particles may shift toward increased coverage of the first metal-
rich core by the second metal-containing shell. This shift
generally comprises leaching of the first metal from the metal
particles at the support surface. Second metal may be removed or
leached from the particles, but to a lesser degree than first
metal is removed from the particles. This behavior has been
observed to provide a shift toward preferred first metal to second
metal atomic ratios.
[00275] Platinum-iron catalysts of the present invention have
been observed to behave as described. That is, during use, iron
and platinum may be leached from the metal particles at the
surface of the catalyst and, more particularly, iron is leached
from the particles to a greater degree than platinum. Leaching in
this manner may proceed in accordance with the "self-correcting"
mechanism described above in connection with platinum-copper
catalysts. However, leaching may also proceed to form platinum-
iron particles of advantageous structures. Rather than
compensating for a relatively low excess of first metal to second
metal to provide a structure in which the atomic ratio of first
metal to second metal is at a suitable excess, leaching of first
metal predominates over any leaching of second metal to such a
degree that one or more particles are provided that exhibit
minimal, if any, excess of first metal to second metal. In fact,
in various embodiments, a catalyst structure exhibiting an excess
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of second metal to first metal is achieved. Although these
particles may not include a first metal-rich alloy or a first
metal-rich core at least partially surrounded by a second metal-
rich shell, they do nonetheless provide improved metal
utilization.
[00276] In various such embodiments, the metal particles at
the surface of the catalyst are in the form of a structure
comprising a discontinuous shell comprising a layer of first metal
atoms and a layer (e.g., monolayer) of second metal atoms at the
surface of the first metal atoms. Reference to a shell in
connection with these embodiments does not indicate the presence
of a continuous or discontinuous shell surrounding a relatively
continuous core. Rather, shell refers to the overall structure of
the resulting particle. The shell structure may surround an inner
region including first metal, but the inner regions of the shell
structure are not in the form of a relatively continuous first
metal-rich core surrounded by the outer regions of the shell
structure. The discontinuous porous shell generally comprises
pores and, more particularly, nanopores (i.e., pores having a size
in their largest dimension of from about 1 to about 6 nanometers
(nm), or from about 2 to about 5 nm). In this manner, the shell
structure may be referred to as a discontinuous nanoporous shell.
In accordance with such embodiments, the atomic ratio of iron
(first metal) to platinum (second metal) is generally less than
1:1, typically from about 0.25:1 to about 0.9:1, more typically
from about 0.4:1 to about 0.75:1 and, more typically, from about
0.4:1 to about 0.6:1 (e.g., about 0.5:1). Further in accordance
with these embodiments, the layer or regions of first metal
generally have a thickness of no more than about 5 first metal
atoms, typically no more than about 3 first metal atoms and, still
more typically, no more than about 2 first metal atoms.
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Additionally or alternatively, the layer or regions of second
metal atoms generally have a thickness of no more than about 5
second metal atoms, typically no more than about 4 second metal
atoms, more typically no more than about 3 second metal atoms and,
more typically, no more than about 2 second metal atoms.
[00277] Extensive leaching of metal from catalyst particles to
form platinum-iron "shell" particles has been observed to occur
during use under certain conditions (e.g., acidic conditions
prevailing during oxidation of PMIDA). Experimental evidence
indicates that catalysts including platinum-iron shell particles
are effective for use in, for example, the liquid phase oxidation
of PMIDA. Thus, rather than simply relying on formation of the
shell structure during use, catalysts including platinum-iron
shell particles may be prepared by a process generally as
described above for preparation of platinum-iron catalysts further
including treatment for leaching of metals from one or more
particles of the catalyst prior to or during use of the catalyst.
Generally, treatment for metal leaching to form platinum-iron
shell particles comprises contacting a platinum-iron catalyst with
a suitable liquid medium. Typically, the liquid medium is acidic
and the catalyst is contacted with the liquid medium at a
temperature of at least about 5 C, or at least about 15 C.
III. Use of Oxidation Catalysts
[00278] Oxidation catalysts of the present invention may be
used for liquid phase oxidation reactions. Examples of such
reactions include the oxidation of alcohols and polyols to form
aldehydes, ketones, and acids (e.g., the oxidation of 2-propanol to
form acetone, and the oxidation of glycerol to form glyceraldehyde,
dihydroxyacetone, or glyceric acid); the oxidation of aldehydes to
form acids (e.g., the oxidation of formaldehyde to form formic
acid, and the oxidation of furfural to form 2-furan carboxylic
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acid); the oxidation of tertiary amines to form secondary amines
(e.g., the oxidation of nitrilotriacetic acid (NTA) to form
iminodiacetic acid (IDA)); the oxidation of secondary amines to
form primary amines (e.g., the oxidation of IDA to form glycine);
and the oxidation of various acids (e.g., formic acid or acetic
acid) to form carbon dioxide and water.
[00279] The above-described catalysts are especially useful in
liquid phase oxidation reactions at pH levels less than 7, and in
particular, at pH levels less than 3. One such reaction is the
oxidation of PMIDA or a salt thereof to form an N-
(phosphonomethyl)glycine product in an environment having pH levels
in the range of from about 1 to about 2. This reaction is often
carried out in the presence of solvents which solubilize noble
metals and, in addition, the reactants, intermediates, or products
often solubilize noble metals.
[00280] The oxidation catalyst disclosed herein is
particularly suited for catalyzing the liquid phase oxidation of a
tertiary amine to a secondary amine, for example in the preparation
of glyphosate and related compounds and derivatives. For example,
the tertiary amine substrate may correspond to a compound of
Formula I having the structure
0 R11
R3 11 __
i2
P
A /
R-0 N¨R1
(Formula I)
wherein R2 is selected from the group consisting of R50C(0)CH2- and
R5OCH2CH2-, R2is selected from the group consisting of R50C(0)CH2-,
R5OCH2CH2-, hydrocarbyl, substituted hydrocarbyl, acyl, -CHR5PO3R2R5,
and -CHR5SO3R25, R% R9 andRil are selected from the group consisting
of hydrogen, alkyl, halogen and -NO2, and R3, R4, R5, R% R5and are
independently selected from the group consisting of hydrogen,
hydrocarbyl, substituted hydrocarbyl and a metal ion. Preferably,
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R2 comprises R50C(0)CH2-, Ril is hydrogen, R5is selected from
hydrogen and an agronomically acceptable cation and R2 isselected
from the group consisting of R50C(0)CH2-, acyl, hydrocarbyl and
substituted hydrocarbyl.
[00281]As noted above, the oxidation catalyst of the present
invention is particularly suited for catalyzing the oxidative
cleavage of a PMIDA substrate to form N-(phosphonomethyl)glycine
product. In such an embodiment, the catalyst is effective for
oxidation of by-product formaldehyde to formic acid, carbon dioxide
and/or water. More particularly, it is currently believed that
catalysts of the present invention may provide improvements in
activity for PMIDA, formaldehyde, and/or formic acid oxidation as
compared to conventional noble metal-containing catalysts, either
generally or on a per unit metal weight basis.
[00282]As is recognized in the art, the liquid phase
oxidation of N-(phosphonomethyl)iminodiacetic acid substrates may
be carried out in a batch, semi-batch or continuous reactor system
containing one or more oxidation reaction zones. The oxidation
reaction zone(s) may be suitably provided by various reactor
configurations, including those that have back-mixed
characteristics, in the liquid phase and optionally in the gas
phase as well, and those that have plug flow characteristics.
Suitable reactor configurations having back-mixed characteristics
include, for example, stirred tank reactors, ejector nozzle loop
reactors (also known as venturi-loop reactors) and fluidized bed
reactors. Suitable reactor configurations having plug flow
characteristics include those having a packed or fixed catalyst bed
(e.g., trickle bed reactors and packed bubble column reactors) and
bubble slurry column reactors. Fluidized bed reactors may also be
operated in a manner exhibiting plug flow characteristics. The
configuration of the oxidation reactor system, including the number
of oxidation reaction zones and the oxidation reaction conditions
are not critical to the practice of the present invention.
Suitable oxidation reactor systems and oxidation reaction
conditions for liquid phase catalytic oxidation of an N-
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(phosphonomethyl)iminodiacetic acid substrate are well-known in the
art and described, for example, by Ebner et al., U.S. Patent No.
6,417,133, by Leiber et al., U.S. Patent No. 6,586,621, and by
Haupf ear et al., U.S. Patent No. 7,015,351.
[00283] The description below discloses with particularity the
use of catalysts described above acting as the catalyst to effect
the oxidative cleavage of a PMIDA substrate to form an N-
(phosphonomethyl)glycine product. It should be recognized,
however, that the principles disclosed below are generally
applicable to other liquid phase oxidative reactions, especially
those at pH levels less than 7 and those involving solvents,
reactants, intermediates, or products which solubilize noble
metals.
[00284] To begin the PMIDA oxidation reaction, it is
preferable to charge the reactor with the PMIDA substrate,
catalyst, and a solvent in the presence of oxygen. The solvent is
most preferably water, although other solvents (e.g., glacial
acetic acid) are suitable as well.
[00285] The reaction may be carried out in a wide variety of
batch, semi-batch, and continuous reactor systems. The
configuration of the reactor is not critical. Suitable
conventional reactor configurations include, for example, stirred
tank reactors, fixed bed reactors, trickle bed reactors, fluidized
bed reactors, bubble flow reactors, plug flow reactors, and
parallel flow reactors.
[00286] When conducted in a continuous reactor system, the
residence time in the reaction zone can vary widely depending on
the specific catalyst and conditions employed. Typically, the
residence time can vary over the range of from about 3 to about 120
minutes. Preferably, the residence time is from about 5 to about
90 minutes, and more preferably from about 5 to about 60 minutes.
When conducted in a batch reactor, the reaction time typically
varies over the range of from about 15 to about 120 minutes.
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Preferably, the reaction time is from about 20 to about 90 minutes,
and more preferably from about 30 to about 60 minutes.
[00287] In a broad sense, the oxidation reaction may be
practiced in accordance with the present invention at a wide range
of temperatures, and at pressures ranging from sub-atmospheric to
super-atmospheric. Use of mild conditions (e.g., room temperature
and atmospheric pressure) have obvious commercial advantages in
that less expensive equipment may be used. However, operating at
higher temperatures and super-atmospheric pressures, while
increasing capital requirements, tends to improve phase transfer
between the liquid and gas phase and increase the PMIDA oxidation
reaction rate.
[00288] Preferably, the PMIDA oxidation reaction is conducted
at a temperature of from about 20 to about 180 C, more preferably
from about 50 to about 140 C, and most preferably from about 80 to
about 110 C. At temperatures greater than about 180 C, the raw
materials tend to begin to slowly decompose.
[00289] The pressure used during the PMIDA oxidation generally
depends on the temperature used. Preferably, the pressure is
sufficient to prevent the reaction mixture from boiling. If an
oxygen-containing gas is used as the oxygen source, the pressure
also preferably is adequate to cause the oxygen to dissolve into
the reaction mixture at a rate sufficient such that the PMIDA
oxidation is not limited due to an inadequate oxygen supply. The
pressure preferably is at least equal to atmospheric pressure.
More preferably, the pressure is from about 30 to about 500 psig,
and most preferably from about 30 to about 130 psig.
[00290] The concentration of the catalyst prepared in
accordance with the present invention in the reaction mixture is
preferably is from about 0.1 to about 10% by weight ([mass of
catalyst
total reaction mass] x 100%). More preferably, the
catalyst concentration preferably is from about 0.1 to about 5% by
weight, still more preferably from about 0.2 to about 5% by weight
and, most preferably, from about 0.3 to about 1.5% by weight.
Concentrations greater than about 10% by weight are difficult to
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filter. On the other hand, concentrations less than about 0.1% by
weight tend to produce unacceptably low reaction rates.
[00291]As noted, catalysts prepared in accordance with the
methods of the present invention provide for efficient metal
utilization. Thus, catalysts of the present invention may provide
sufficient activity at lower catalyst loadings as compared to
loadings associated with conventional noble metal-containing
catalysts. Accordingly, catalysts loadings in accordance with the
present invention may suitably be at or near the lower limits of
the above-noted ranges. However, it is to be understood that
utilizing a lower catalyst loading is not a critical aspect of the
present invention. In fact, a further aspect of the present
invention involves utilizing the catalysts of the present invention
at loadings similar to those associated with conventional noble
metal-containing catalysts while providing improved catalytic
activity based on the improvements in metal utilization.
[00292] The concentration of PMIDA substrate in the feed
stream is not critical. Use of a saturated solution of PMIDA
substrate in water is preferred, although for ease of operation,
the process is also operable at lesser or greater PMIDA substrate
concentrations in the feed stream. If the catalyst is present in
the reaction mixture in a finely divided form, it is preferred to
use a concentration of reactants such that all reactants and the N-
(phosphonomethyl)glycine product remain in solution so that the
catalyst can be recovered for re-use, for example, by filtration.
On the other hand, greater concentrations tend to increase reactor
through-put. Alternatively, if the catalyst is present as a
stationary phase through which the reaction medium and oxygen
source are passed, it may be possible to use greater concentrations
of reactants such that a portion of the N-(phosphonomethyl)glycine
product precipitates.
[00293] Normally, a PMIDA substrate concentration of up to
about 50% by weight ([mass of PMIDA substrate
total reaction
mass] x 100%) may be used (especially at a reaction temperature of
from about 20 to about 180 C). Preferably, a PMIDA substrate
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concentration of up to about 25% by weight is used (particularly at
a reaction temperature of from about 60 to about 150 C). More
preferably, a PMIDA substrate concentration of from about 12 to
about 18% by weight is used (particularly at a reaction temperature
of from about 100 to about 130 C). PMIDA substrate concentrations
below 12% by weight may be used, but are less economical because a
relatively low payload of N-(phosphonomethyl)glycine product is
produced in each reactor cycle and more water must be removed and
energy used per unit of N-(phosphonomethyl)glycine product
produced. Relatively low reaction temperatures (i.e., temperatures
less than 100 C) often tend to be less advantageous because the
solubility of the PMIDA substrate and N-(phosphonomethyl)glycine
product are both relatively low at such temperatures.
[00294] The oxygen source for the PMIDA oxidation reaction may
be any oxygen-containing gas or a liquid comprising dissolved
oxygen. Preferably, the oxygen source is an oxygen-containing gas.
As used herein, an oxygen-containing gas is any gaseous mixture
comprising molecular oxygen which optionally may comprise one or
more diluents which are non-reactive with the oxygen or with the
reactant or product under the reaction conditions.
[00295] Examples of such gases are air, pure molecular oxygen,
or molecular oxygen diluted with helium, argon, nitrogen, or other
non-oxidizing gases. For economic reasons, the oxygen source most
preferably is air, oxygen-enriched air, or pure molecular oxygen.
[00296] Oxygen may be introduced by any conventional means
into the reaction medium in a manner which maintains the dissolved
oxygen concentration in the reaction mixture at a desired level.
If an oxygen-containing gas is used, it preferably is introduced
into the reaction medium in a manner which maximizes the contact of
the gas with the reaction solution. Such contact may be obtained,
for example, by dispersing the gas through a diffuser such as a
porous frit or by stirring, shaking, or other methods known to
those skilled in the art.
[00297] The oxygen feed rate preferably is such that the PMIDA
oxidation reaction rate is not limited by oxygen supply. If the
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dissolved oxygen concentration is too high, however, the catalyst
surface tends to become detrimentally oxidized, which, in turn,
tends to lead to more leaching of noble metal present in the
catalyst and decreased formaldehyde activity (which, in turn, leads
to more NMG being produced). Generally, it is preferred to use an
oxygen feed rate such that at least about 40% of the oxygen is
utilized. More preferably, the oxygen feed rate is such that at
least about 60% of the oxygen is utilized. Even more preferably,
the oxygen feed rate is such that at least about 80% of the oxygen
is utilized. Most preferably, the rate is such that at least about
90% of the oxygen is utilized. As used herein, the percentage of
oxygen utilized equals: (the total oxygen consumption rate oxygen
feed rate) x 100%. The term "total oxygen consumption rate" means
the sum of: (i) the oxygen consumption rate ("Rr") of the oxidation
reaction of the PMIDA substrate to form the N-
(phosphonomethyl)glycine product and formaldehyde, (ii) the oxygen
consumption rate ("R_") of the oxidation reaction of formaldehyde
to form formic acid, and (iii) the oxygen consumption rate ("R_")
of the oxidation reaction of formic acid to form carbon dioxide and
water.
[00298] In various embodiments of this invention, oxygen is
fed into the reactor as described above until the bulk of PMIDA
substrate has been oxidized, and then a reduced oxygen feed rate is
used. This reduced feed rate preferably is used after about 75% of
the PMIDA substrate has been consumed. More preferably, the
reduced feed rate is used after about 80% of the PMIDA substrate
has been consumed. Where oxygen is supplied as pure oxygen or
oxygen-enriched air, a reduced feed rate may be achieved by purging
the reactor with (non-enriched) air, preferably at a volumetric
feed rate which is no greater than the volumetric rate at which the
pure molecular oxygen or oxygen-enriched air was fed before the air
purge. The reduced oxygen feed rate preferably is maintained for
from about 2 to about 40 minutes, more preferably from about 5 to
about 20 minutes, and most preferably from about 5 to about 15
minutes. While the oxygen is being fed at the reduced rate, the
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temperature preferably is maintained at the same temperature or at
a temperature less than the temperature at which the reaction was
conducted before the air purge. Likewise, the pressure is
maintained at the same or at a pressure less than the pressure at
which the reaction was conducted before the air purge. Use of a
reduced oxygen feed rate near the end of the PMIDA reaction allows
the amount of residual formaldehyde present in the reaction
solution to be reduced without producing detrimental amounts of
AMPA by oxidizing the N-(phosphonomethyl)glycine product.
[00299] Reduced losses of noble metal may be observed with
this invention if a sacrificial reducing agent is maintained or
introduced into the reaction solution. Suitable reducing agents
include formaldehyde, formic acid, and acetaldehyde. Most
preferably, formic acid, formaldehyde, or mixtures thereof are
used. Experiments conducted in accordance with this invention
indicate that if small amounts of formic acid, formaldehyde, or a
combination thereof are added to the reaction solution, the
catalyst will preferentially effect the oxidation of the formic
acid or formaldehyde before it effects the oxidation of the PMIDA
substrate, and subsequently will be more active in effecting the
oxidation of formic acid and formaldehyde during the PMIDA
oxidation. Preferably from about 0.01 to about 5% by weight ([mass
of formic acid, formaldehyde, or a combination thereof total
reaction mass] x 100%) of sacrificial reducing agent is added, more
preferably from about 0.01 to about 3% by weight of sacrificial
reducing agent is added, and most preferably from about 0.01 to
about 1% by weight of sacrificial reducing agent is added.
[00300] In certain embodiments, unreacted formaldehyde and
formic acid are recycled back into the reaction mixture for use in
subsequent cycles. In this instance, an aqueous recycle stream
comprising formaldehyde and/or formic acid also may be used to
solubilize the PMIDA substrate in the subsequent cycles. Such a
recycle stream may be generated by evaporation of water,
formaldehyde, and formic acid from the oxidation reaction mixture
in order to concentrate and/or crystallize product
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N-(phosphonomethyl)glycine. Overheads condensate containing
formaldehyde and formic acid may be suitable for recycle.
[00301] Typically, the concentration of
N-(phosphonomethyl)glycine in the product mixture may be as great
as 40% by weight, or greater. Preferably, the
N-(phosphonomethyl)glycine concentration is from about 5 to about
40%, more preferably from about 8 to about 30%, and still more
preferably from about 9 to about 15%. Concentrations of
formaldehyde in the product mixture are typically less than about
0.5% by weight, more preferably less than about 0.3%, and still
more preferably less than about 0.15%.
[00302] Following the oxidation, the catalyst preferably is
subsequently separated by filtration. The
N-(phosphonomethyl)glycine product may then be isolated by
precipitation, for example, by evaporation of a portion of the
water and cooling.
[00303] In certain embodiments, it should be recognized that
the catalyst of this invention has the ability to be reused over
several cycles, depending on how oxidized its surface becomes with
use. Even after the catalyst becomes heavily oxidized, it may be
reused by being reactivated. To reactivate a catalyst having a
heavily oxidized surface, the surface preferably is first washed to
remove the organics from the surface. It then preferably is
reduced in the same manner that a catalyst is reduced after the
noble metal is deposited onto the surface of the support, as
described above.
[00304]Noble metal-containing catalysts including a treated
porous substrate prepared by the present method may also be used
in combination with a supplemental promoter as described, for
example, in U.S. Patent No. 6,586,621, U.S. Patent No. 6,963,009.
(00305]N-(phosphonomethyl)glycine product prepared in
accordance with the present invention may be further processed in
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accordance with many well-known methods in the art to produce
agronomically acceptable salts of N-(phosphonomethyl)glycine
commonly used in herbicidal glyphosate compositions. As used
herein, an "agronomically acceptable salt" is defined as a salt
which contains a cation(s) that allows agriculturally and
economically useful herbicidal activity of an N-
(phosphonomethyl)glycine anion. Such a cation may be, for example,
an alkali metal cation (e.g., a sodium or potassium ion), an
ammonium ion, an isopropyl ammonium ion, a tetra-alkylammonium ion,
a trialkyl sulfonium ion, a protonated primary amine, a protonated
secondary amine, or a protonated tertiary amine.
IV. Additional Embodiments
A. Pore Blocking
[00306] With regard to disposing or depositing a pore blocking
compound within substrate pores as detailed elsewhere herein, it
is to be noted that the present invention is not limited to
disposing or depositing a pore blocking compound within the
smallest substrate pores (e.g., micropores). That is, various
embodiments of the present invention are directed to disposing or
depositing a pore blocker within pores of an intermediate or
larger size range. In this manner, various embodiments of the
present invention provide further opportunities for controlling
the sizes of pores that are blocked (i.e., further opportunities
for controlling, or tuning blocking of pores). For example, in
addition to micropores, porous carbon supports that may be treated
by the present method have pores of larger dimensions (e.g., pores
having a largest dimension of from about 20A to about 3000A).
[00307] Disposing or depositing a pore blocking agent within
pores of a size above the micropore size range proceeds generally
in accordance with the above-described method. For example, the
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substrate may be contacted with the pore blocking compound and/or
one or more precursors. Further in accordance with the above-
described method, the pore blocker may be retained within the
targeted pores by virtue of exhibiting at least one dimension
larger than the openings of the targeted pores. And regardless of
whether the pore blocking agent is introduced into the targeted
pores or formed in situ, the pore blocker may be retained within
the targeted pores by virtue of a conformational arrangement of
the pore blocker.
[00308] As noted above, when relatively small pores are
targeted by the pore blocker, the pore blocker may enter the non-
targeted pores and subsequently exit therefrom (e.g., by virtue of
contacting with a liquid washing medium). It is to be noted that
a pore blocker targeting intermediate and/or larger size may not
enter the pores smaller than the targeted pores. However, this
does not impact the goal of blocking of intermediate and/or larger
sized pores.
[00309] It is currently believed that a variety of compounds
are suitable as pore blocking compounds for the purpose of
blocking pores above the micropore size range. For example, the
pore blocker may be selected from the group consisting of various
hydrophilic polymers (e.g., various polyethylene glycols), and
combinations thereof.
[00310] In various embodiments, the intermediate and/or larger
size pore blocker may comprise the product of a reaction between
one or more pore blocking compound precursors. For example, it
has been observed that the coupling product of a ketone and a
dihydric alcohol may be utilized as a pore blocker.
[00311] As with micropores as noted above, it is believed that
the presence of the pore blocking compound within targeted pores
outside the micropore domain will cause at least a portion of the
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"blocked" pores to appear as a non-porous portion of the substrate
during surface area measurements, thereby reducing the proportion
of surface area that would otherwise be provided by the targeted
pores if they were not blocked. This blocking of the targeted
pores is currently believed to provide a reduction in the surface
area of the treated substrate provided by the targeted pores. For
example, in various embodiments, the surface area of the treated
substrate provided by the pores outside (i.e., above) the
micropore size range is generally no more than about 80% or no
more than about 70% of the surface area of the substrate provided
by these pores prior to treatment. Typically, the surface area of
the treated substrate provided by the targeted pores is no more
than about 60% and more typically no more than about 50% of the
surface area of the substrate provided by these pores prior to
treatment.
B. Pore Blocking of Catalyst Pores
[00312] As noted, persistence of the pore blocker in treated
substrates of the present invention is not critical to provide the
advantages described above (e.g., a reduced proportion of metal
crystallites at the surface of a porous carbon support among
relatively small pores of the substrate surface). And it is
currently believed that the pore blocker is most likely decomposed
and/or otherwise removed from the substrate surface before
calcining. In various alternative embodiments, the methods for
treating porous substrates may be applied to treatment of finished
catalysts. For example, catalysts comprising a noble metal
deposited onto a carbon support may be treated by depositing a
pore blocker at the surface of the catalyst within its relatively
small pores. It is currently believed that the presence of the
pore blocker within the relatively small pores may promote
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preferential contact of reactants with the deposited metal among
the intermediate and larger-sized porous regions within which the
deposited metal is more accessible to the reactants. In this
manner, conversion of reactants to products may be promoted by
reducing the proportion of reactants that contact deposited metal
among the relatively small porous regions in which the deposited
metal may be relatively inaccessible to the reactants. By way of
further example, treating carbon-supported catalysts suitable for
in preparation of DSIDA from DEA in accordance with the methods
detailed are currently believed to provide catalysts including a
reduced proportion of exposed noble metal and, accordingly,
reduced by-product (e.g., glycine and/or oxalate). However, it is
to be understood that treatment of finished catalyst (i.e., carbon
or metal-containing having one or more metals deposited thereon)
is not a critical aspect of the invention and that catalysts
prepared using substrates treated by the present methods have
proven to be effective catalysts.
C. Non-carbon supports
[00313] In addition to treatment of porous carbon supports as
detailed herein, the method of the present invention for blocking
certain pores of a substrate may be used to treat non-carbonaceous
supports. More particularly, the methods detailed herein may be
used for treatment of porous metal alloys often referred to as
metal sponges. Metal sponge alloys that may be treated by the
present method are described, for example, in U.S. Patent No.
5,627,125, U.S. Patent No. 5,916,840, U.S. Patent No. 6,376,708,
and U.S. Patent No. 6,706,662 = It is
currently believed that treated metal-containing substrates may
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exhibit one or more of the above-noted properties concerning
treated porous carbon substrates.
D. Preparation of Carboxylic Acids
[00314] In addition to PMIDA oxidation as detailed elsewhere
herein, catalysts including treated substrates prepared by the
present method are currently believed to be suitable for use in
other reactions. For example, catalysts including treated
substrates prepared by the present method may be used in the
preparation of carboxylic acids including, for example, the
preparation of disodiumiminodiacetic acid (DSIDA) by
dehydrogenation of diethanolamine (DEA). More particularly,
catalysts including treated substrates of the present invention
may address one or more issues that may be observed with
conventional catalysts utilized in preparation of carboxylic acids
such as DSIDA. For example, suitable catalysts often include
copper deposited over the surface of a carbon support having a
noble metal (e.g., platinum or palladium) at its surface. It is
currently believed that at least a portion, and possibly a
significant fraction of the noble metal may remain exposed after
deposition of the copper. Excessive exposed noble metal is
undesired since it is believed to promote formation of various
undesired by-products (e.g., glycine and oxalate). A substantial
portion, if not nearly all the exposed noble metal is believed to
be at the surface of the support within relatively small pores
that are inaccessible to copper during its deposition. Other
catalysts suitable for preparation of carboxylic acids include
copper deposited at the surface of metal-containing (e.g., nickel-
containing) sponges. As with exposed noble metal at the surface
of carbon-supported catalysts, metal support surface that is not
coated by the copper within relatively small pores of the metal
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sponge support are believed to contribute to formation of
undesired by-products. It is currently believed that selective
blocking of relatively small pores of substrates in accordance
with the methods detailed herein may be used to prepare effective
carbon- and metal-supported catalysts that may address one or more
of the above-noted issues.
[00315] Preparation of DSIDA from DEA using a catalyst
comprising a substrate treated as detailed herein generally
proceeds in accordance with methods known in the art including,
for example, U.S. Patent Nos. 5,627,125, U.S. Patent No.
5,916,840, U.S. Patent No. 6,376,708, and U.S. Patent No.
6,706,662.
[00316] The present invention is illustrated by the following
examples which are merely for the purpose of illustration and not
to be regarded as limiting the scope of the invention or the
manner in which it may be practiced.
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EXAMPLES
[00317] The following non-limiting examples are provided to
further illustrate the present invention.
I. Pore Plugging
Example 1
[00318] Three carbon supports were treated to determine the
effectiveness of candidate pore blocking compounds. Support A had
a total Langmuir surface area of approximately 1500 m2/g (including
total micropore surface area of approximately 1279 m2/g and total
macropore surface area of approximately 231 m2/g). Support B had a
total Langmuir surface area of approximately 2700 m2/g (including
total micropore surface area of approximately 1987 m2/g and total
macropore surface area of approximately 723 m2/g). Support C had a
total Langmuir surface area of approximately 1100 m2/g (including
total micropore surface area of approximately 876 m2/g and total
macropore surface area of approximately 332 m2/g).
[00319] The candidate pore blocking compounds were 1,4-
cyclohexanedione, ethylene glycol, and the diketal product of a
coupling reaction between 1,4-cyclohexanedione and ethylene glycol
(i.e., 1,4-cyclohexanedione bis(ethylene ketal)).
[00320] Support samples (30 g) were contacted with a solution
of 1,4-cyclohexanedione in ethylene glycol (6g/40g) at
approximately 25 C for approximately 60 minutes. The pH of the
slurry was adjusted to approximately 1 by addition of concentrated
hydrochloric acid and agitated by stirring for approximately 60
minutes. The pH of the slurry was then adjusted to approximately
8.5 by addition of 50 wt.% sodium hydroxide solution. The slurry
was then filtered to isolate the treated support, which was washed
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using deionized water at a temperature of approximately 90 C.
(mechanism one)
[00321] Support samples (2 g) were also contacted with a
solution of 1,4-cyclohexanedione bis(ethylene ketal) in water
(0.6g/40g) at approximately 25 C for approximately 60 minutes.
(mechanism two)
[00322] As controls, samples of carbon A were also separately
treated by contact with (1) ethylene glycol and (2) 1,4-
cyclohexanedione.
[00323] The treated supports were analyzed by the well-known
Langmuir method to determine their surface area (SA) profiles
(e.g., total surface area, surface area attributed to micropores,
and surface area attributed to macropores). The results are shown
in Table 1.
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Table 1
% of original % of original
Support Mechanism micropore SA macropore SA
Carbon A One 24.2 74.9
Carbon A Two 34.4 70.9
Carbon A Control One 93.7 98.7
Carbon A Control Two 68.9 94.4
Carbon B One 55.6 78.7
Carbon B Two 65.4 81.5
Carbon C One 17.9 76.8
Carbon C Two 22 72.3
[00324] As shown, both mechanism one and mechanism two
provided a reduction in micropore and macropore surface areas for
each of supports A-C, and more particularly a greater reduction in
micropore surface area as compared to the reduction in macropore
surface area (e.g., a three times greater reduction in micropore
surface area). The percentage reduction in surface area for
carbon B is believed to be lower than that observed for the other
two carbons because of its higher surface area. However, it
should be noted that the percentage of micropore surface area
reduction for carbon B nonetheless corresponds to an absolute
reduction of approximately 900 m2/g.
[00325] The control testing of carbon A with ethylene glycol
provided minimal reduction in micropore and macropore surface
areas, while the control testing with 1,4-cyclohexanedione
provided a greater reduction in micropore and macropore surface
areas, but to a much lesser degree than associated with both
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mechanism one and mechanism two. Thus, it is believed that the
components combine to form the pore blocking compound that
provides greater reduction in surface area than either component
alone or the cumulative reduction provided by each.
Example 2
[00326] Carbons A, B, and C (30 g) described in Example 1 were
each treated by contacting with solutions of
1,4-cyclohexanedione in ethylene glycol (6 g/40 g) at
approximately 25 C for approximately 60 minutes. Each carbon was
also treated by contacting with solutions of 1,3-cyclohexanedione
in ethylene glycol (1 g/50 g) at approximately 25 C for
approximately 120 minutes. Carbon C was also treated by contacting
with a solution of 1,4-cyclohexanedione in 1,2-propanediol (1 g/50
g) at approximately 25 C for approximately 60 minutes. Surface area
analysis results are shown in Table 2. As shown, each combination
of dione and diol provided reduction of micropore and macropore
surface areas, and more particularly preferential reduction in
micropore surface area.
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Table 2
% of original % of original
Sample Diane Dial micropore SA macropore SA
1,4- Ethylene
Carbon A disubstituted Glycol 22.6 75.8
1,3- Ethylene
Carbon A disubstituted Glycol 58.4 84
1,4- Ethylene
Carbon B disubstituted Glycol 55.6 78.7
1,3- Ethylene
Carbon B disubstituted Glycol 32.2 39.8
1,4- Ethylene
Carbon C disubstituted Glycol 17.9 76.8
1,3- Ethylene
Carbon C disubstituted Glycol 45 75.6
1,4- 1,2-
Carbon C disubstituted Propanediol 14.4 67.5
1,3- 1,2-
Carbon C disubstituted Propanediol 56.1 80.7
Example 3
[00327] This example provides transmission electron microscopy
results (TEM) for a platinum on carbon catalyst prepared using
Carbon B treated as described in Example 1 (mechanism one). The
catalyst contained approximately 5 wt.% platinum and was prepared
generally as detailed herein (e.g., by liquid phase deposition of
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platinum onto the treated carbon support), followed by treatment
at elevated temperatures in a non-oxidizing environment. For
comparison purposes, a catalyst including 5 wt.% platinum on
Carbon B that was not treated was also analyzed. The TEM analysis
was conducted generally as described by Wan et al. in
International Publication No. WO 2006/031198.
[00328] The results for the catalyst including the untreated
and treated carbons are shown in Figs. 3A/5A and 3B/5B,
respectively. These results suggest a reduction in relatively
small platinum-containing particles (e.g., having a particle size
less than 4 nm) for the catalyst prepared using the treated
support.
[00329] The TEM results generally correspond to high density
regions of the substrates including primarily micropores and these
results indicate higher platinum density among these regions for
the catalyst including the untreated support.
Example 4
[00330] This example provides surface area analysis results
for a carbon support of the type described in U.S. Patent Nos.
4,624,937 and 4,696,771 to Chou et al. (designated MC-10) treated
in accordance with the present invention. Support samples were
treated in accordance with both mechanism one and mechanism two
described above in Example 1. The support had an initial
micropore Langmuir surface area of approximately 1987 m2/g and an
initial macropore Langmuir surface area of approximately 723 m2/g.
Micropore and macropore surface area retention results for the
treated supports are shown in Table 3.
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Table 3
% of original % of original
Support Plugging Mechanism micropore SA macropore SA
MC-10 One 55.6 78.7
MC-10 Two 65.4 81.5
_
[00331] Figs. 4A and 4B provide pore volume data for untreated
and treated MC-10 supports.
Example 5
[00332] This example provides results of carbon monoxide (CO)
chemisorption analysis for the platinum-containing catalysts of
Example 4. CO chemisorption is an analysis method suitable for
estimating the proportion of exposed metal, and the analysis was
conducted generally in accordance with "Protocol A" described in
Example 67 herein and Example 23 of WO 2006/031938.
[00333] The results are shown in Table 4. The lower CO
chemisorption for the catalyst including a treated carbon support
(38.6 and 43.3 mol CO/gram versus 54.7 mol CO/gram catalyst)
indicate a reduced proportion of exposed noble metal for the
platinum-containing catalyst prepared using the treated carbon
support.
Table 4
Cycle 2
CO gmol/
Catalyst g catalyst
Pt on regular MC-10 54.7
Pt on modified MC-10 38.6/43.3
=
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Example 6
[00334] Catalysts containing approximately 5 wt.% Pt and
approximately 0.5 wt.% Fe were prepared generally as detailed
herein using untreated MC-10 carbon supports, and MC-10 carbon
supports treated in accordance with both mechanism one and
mechanism two described in Example 1. These catalysts were tested
in PMIDA oxidation generally under the conditions set forth in
Example 7; the results are shown in Table 5. The Catalyst (1)
included an untreated support. Catalysts (2) and (3) each
included supports treated in accordance with mechanism two
detailed above in Example 1. Catalyst (2) was prepared by a
method that included filtration of the copper-impregnated support
prior to platinum deposition. Catalyst (3) was prepared by a
method that did not include filtration of the copper-impregnated
support prior to platinum deposition (i.e., a one-pot method as
described in Example 16).
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Table 5
Catalyst (1)
Run Number 1 2 3 4 5 6
Run Time,
min 43.0 46.2 47.8 50.6 50.8 52.0
GLY wt.% 5.413 5.600 5.620 5.678 5.556 5.748
PMIDA wt.% 0.034 0.034 0.094 0.134 0.075 0.149
CH20 wt.% 0.150 0.182 0.199 0.211 0.190 0.209
FORMIC wt.
% 0.384 0.455 0.521 0.516 0.505 0.512
IDA wt.% 0.074 0.046 0.031 0.030 0.030 0.027
Pt in
soln.
(Pim) 0.03 0.07 0.07 0.09 0.08 0.12
Fe in
soln.(ppm) 5.4 1.9 2.3 2.3 2.0 1.6
Catalyst (2)
Run Number 1 2 3 4 5 6
Run Time,
min 43.0 45.1 48.8 47.2 47.6 48.3
GLY wt.% 5.363 5.543 5.541 5.592 5.557 5.604
PMIDA wt.% 0.036 0.097 0.022 0.129 0.154 0.177
CH20 wt.% 0.125 0.143 0.105 0.139 0.144 0.169
FORMIC wt.
% 0.389 0.456 0.435 0.479 0.484 0.508
IDA wt.% 0.086 0.052 0.041 0.033 0.031 0.028
Pt in
soln.(ppm) 0.05 0.14
Fe in 6.3 1.9
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soln.(ppm)
Catalyst (3)
Run Number 1 2 3 4 5 6
Run Time,
min 43.0 46.3 46.7 48.5 48.5 49.8
GLY wt.% 5.475 5.596 5.543 5.649 5.790 5.980
PMIDA wt.% 0.058 0.141 0.167 0.136
CH20 wt.% 0.175 0.171 0.192 0.191 0.208 0.222
FORMIC wt.
% 0.466 0.505 0.547 0.565
IDA wt.% 0.073 0.044 0.030 0.026 0.025 0.022
Pt in
soln.(ppm)
Fe in
soln.(ppm)
GLY = Glyphosate IDA = Iminodiacetic Acid
FORMIC = Formic Acid ppm = Parts Per Million
II. Catalyst Precursors; First and Second Metal-Containing
Catalysts; Catalyst Precursor Structures
[00335] The following Examples describe preparation of
catalysts as detailed herein, their testing by various
characterization methods, and their testing in PMIDA oxidation.
The following Examples also provide comparisons of catalysts
prepared as detailed herein, and various other metal-containing
carbon-supported catalysts. For example, the following Examples
provide comparisons to carbon-supported catalysts including 5 wt.%
Pt, 0.1 wt.% Fe, and 0.4 wt.% Co, and carbon-supported catalysts
including 5 wt.% Pt and 0.5 wt.% Fe. These catalysts were
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prepared generally as described by Wan et al. in International
Publication No. WO 2006/031938.
Example 7
[00336] Catalysts prepared as described herein and comparison
samples were tested in PMIDA oxidation conditions also generally
described by Wan et al. in International Publication No. WO
2006/031938. For example, PMIDA oxidation cycles were conducted
in a glass reactor (200 ml commercially available from Ace Glass
Inc.) containing a reaction mass (approx. 140 g) which included
water (approx. 128 g), approximately 8.2 wt.% PMIDA (approx. 11.48
g), and a catalyst loading of approximately 0.18 wt.% (0.25 g).
The oxidations were generally conducted at a temperature of
approximately 100 C, under a pressure of approximately 60 psig, and
an oxygen flow rate of approximately 100 cc/min. Unless noted
otherwise, reaction cycles were conducted to an endpoint
determined by generation of approximately 1600 cm3 of carbon
dioxide.
[00337] As described in the following Examples and
accompanying figures, various data were collected, including cycle
time, metal leaching, residual formaldehyde (HCHO) content,
residual formic acid (HCOOH) content, iminodiacetic acid (IDA)
formation, N-methyl-N-(phosphonomethyl)glycine (NMG) formation,
total carbon dioxide (CO2) generation, etc.
Example 8
[00338] This example details preparation of a catalyst
containing a nominal Pt content of approximately 2.5 wt.% and a
nominal Cu content of approximately 5 wt.% Cu on an activated
carbon support having a Langmuir surface area of approximately
1500 m2/g.
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[00339] Activated carbon (approx. 10g), CuS0405H20 solution
(approx. 2.07 g), sucrose (approx. 5.67 g), degassed deionized
water (approx. 30g), and degassed 1M NaOH (70 g) were mixed in a
baffled beaker. The mixture was agitated at ambient conditions
(approx. 25 C) for approx. 20 minutes. Formaldehyde (approx. 2.25
g of 37 wt.% solution) was added to the mixture and the resulting
slurry was heated to approx. 30 C and agitated for approx. 60
minutes.
[00340] The resulting slurry was filtered, washed with
degassed deionized water, re-slurried in deionized water, and 1M
HC1 was added to provide a pH of approx. 1.5.
[00341] A solution of K2PtC14 (approx. 0.557 g) in degassed
water (15 g) was added to the slurry, followed by continued
stirring for 60 minutes at ambient conditions. The slurry was
filtered, and the recovered metal-impregnated support was washed
with water, and dried under vacuum at approx. 110 C. A total of
12.12 g of dried metal-impregnated support was recovered.
Elemental analysis indicated a composition of approx. 2.04wt.%. Pt
and approx. 1.93 wt.% Cu on carbon.
[00342] The catalyst precursor was then heated at elevated
temperatures up to approximately 815 C in the presence of a
hydrogen/argon stream (2%/98%; v/v) for approximately 60 minutes.
Elemental analysis indicated final metal contents of approx. 2.34%
wt. Pt and approx. 2.22 wt.% Cu.
[00343] As detailed below, catalysts prepared by heating the
metal-impregnated support at varying temperatures were also
tested. In addition, various metal-impregnated supports were also
tested for their catalytic activity.
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Example 9 (copper plating at ambient temperature)
[00344] Preparation of nominal 2%Pt3.45%Cu on activated carbon
catalyst: The following were added to a baffled beaker including
approx. lOg of activated carbon: CuS0405H20 solution (1.410 g),
3.866 g of sucrose, 90 g of degassed deionized water, and 5.974 g
of 50 wt.% NaOH. The mixture was stirred at approx. 22 C for
approx. 10 minutes using a mechanical agitator. Following
stirring, approx. 1.468g of 37 wt.% formaldehyde solution was
added and the resulting slurry was stirred at approx. 22 C for 60
minutes. The slurry was then filtered and washed twice in the
filter, and then re-slurried in water to pH of approx. 2.0 by
addition of 1.5M degassed HC1. To this slurry was added a
solution of K2PtC14 (0.444 g) in 15 g of degassed water, followed
by stirring for approximately 60 minutes under ambient conditions.
The slurry was then heated to approx. 65 C, followed by stirring
for an additional 30 minutes. The resulting slurry was then
filtered and washed with water and dried under vacuum at approx.
110 C. A total of 11.389g of dried material was recovered.
Example 10
[00345] Preparation of nominal 2.5%Pt5%Cu on activated carbon:
The following was added to approx. lOg of activated carbon in a
baffled beaker: 2.072g of a CuS0405H20 solution, 5.694 g of
sucrose, 30g of degassed deionized water, and 70g of degassed 1M
NaOH was added. The mixture was heated to approx. 35 C using a
mechanical agitator. To this mixture was added 2.249g of 37 wt.%
formaldehyde solution and the resulting slurry was heated to
approx. 33-35 C, followed by continued stirring for 60 minutes.
The slurry was filtered and washed with degassed deionized water
in the filter, and then re-slurried in water at pH of approx. 1.5
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by adding 0.5M HC1. A solution of 0.557g of K2PtC14 in 15g of
degassed water was then added to the slurry, followed by continued
stirring for 60 minutes under ambient conditions. Then the slurry
was heated to approx. 60 C and stirred for an additional 30
minutes. The resulting slurry was filtered and washed with water,
and dried under vacuum at approx. 110 C. A total of 11.701g of
dried material was recovered. Upon heat treatment to a maximum
temperature of approx. 950 C in the presence of an argon/hydrogen
atmosphere (2%/98%) (v/v) for 120 minutes, a final catalyst
composition indicating a weight loss of approximately 12.1 wt.%
during heating was recovered.
Example 11 (no washing after copper deposition)
[00346] Preparation of nominal 2%Pt4%Cu on activated carbon:
The following was added to a baffled beaker including approx. 10g
of activated carbon: 1.643g of CuS0405H20 solution, 4.509 g of
sucrose, 90g of degassed deionized water, and 4.625g of 50wt.%
NaOH. The mixture was heated to approx. 30 C for approx. 10
minutes with a mechanical agitator. To this slurry was added
1.706g of 37 wt.% formaldehyde solution and the resulting slurry
was heated to approx. 30-35 C, followed by continued stirring for
approx. 90 minutes. Then the slurry was filtered, and then without
washing re-slurried in water to pH 2.02 by adding 1M degassed HC1.
A solution of 0.454g of K2PtC14 in 10g of degassed water was then
added to the slurry, followed by continued stirring for 60 minutes
at ambient conditions. The resulting slurry was then heated to
approx. 60 C and stirred for an additional 30 minutes. This slurry
was then filtered and washed with water, and dried under vacuum at
approx. 110 C. A total of 11.720 g of dried material was
recovered. During heat treatment to a maximum temperature of
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approximately 950 C in the presence of an argon/hydrogen atmosphere
(2%/98%) (v/v) for approximately 120 minutes, the sample lost
approximately 13.5% weight.
Example 12
[00347] Preparation of nominal 2%Pt3.75%Cu on activated
carbon: The following was added to a baffled beaker including
approx. 10 g of activated carbon 1.533g of CuS0405H20 solution,
4.210 g of sucrose, 90g of degassed deionized water, and 4.300g of
50 wt.% NaOH was added. This mixture was heated to approx. 30 C
and stirred for approx. 10 minutes using a mechanical agitator.
To this mixture was added 1.507g of 37 wt.% formaldehyde and the
slurry was heated to approx. 30-35 C, followed by continued
stirring for 60 minutes. The slurry was filtered and the recovered
solids washed once in the filter, and then re-slurried in water to
a pH of 1.97 by adding 1M degassed HC1. A solution of 0.452g of
K2PtC14 in 10g of degassed water was then added to the slurry,
followed by continued stirring for 60 minutes under ambient
conditions. Then the slurry was heated to approx. 60 C and stirred
for 30 more minutes. The slurry was filtered and washed with
water, dried under vacuum at approx. 110 C. A total of 11.413g of
dried material was recovered. Upon heat treatment to a maximum
temperature of approximately 950 C in the presence of a 2%/98%
(v/v) H2/Ar atmosphere for 120 minutes, the sample lost
approximately 12.5% weight.
Example 13 (platinum deposition at higher temperature)
[00348] Preparation of nominal 2%Pt4%Cu on activated carbon:
The following were added to a baffled beaker including 10g of
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activated carbon: 1.645g of CuS0405H20 solution, 4.502 g of
sucrose, 90g of degassed deionized water, and 4.636g of 50wt.%
NaOH. The mixture was stirred under ambient conditions for
approx. 20 minutes with a mechanical agitator. Then 1.721g of 37%
formaldehyde was added and the slurry was heated to approx. 30-
35 C, followed by continued stirring for 70 minutes. Then the
slurry was filtered and washed once in the filter, and then re-
slurried in water to pH 2.95 by adding 1M degassed HC1. A
solution of 0.455g of K2PtC14 in 10g of degassed water was then
added to the slurry, followed by continued stirring for 45 minutes
at 40-45 C. Then the slurry was heated to 60 C and stirred for 30
more minutes. The slurry was filtered and the recovered solids
washed with water, and dried under vacuum at approx. 110 C. A
total of 12.008g of dried material was recovered. Upon heat
treatment at a maximum temperature of approx. 950 C in the presence
of a (2%/98%)(v/v) H2/Ar atmosphere for approx. 120 minutes, the
sample lost approximately 12.6% weight.
Example 14
[00349] Preparation of nominal 3%Pt6%Cu on activated carbon:
The following were added to a baffled beaker including 10g of
activated carbon: 2.507g of CuS0405H20 solution, 6.878 g of
sucrose, 90g of degassed deionized water, and 6.974g of 50wt.%
NaOH. The mixture was heated to 30 C and stirred for approx. 10
minutes with a mechanical agitator. Then 2.444g of 37%
formaldehyde was added and the slurry was heated to approx. 35-
37 C, followed by continued stirring for 45 minutes. Then the
slurry was filtered and washed twice in the filter, and then re-
slurried in water to pH 1.97 by adding 1M degassed HC1. A solution
of 0.700g of K2PtC14 in 20g of degassed water was then added to the
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slurry, followed by continued stirring for 60 minutes under
ambient conditions. Then the slurry was heated to 60 C and stirred
for an additional 30 minutes. The slurry was then filtered and
washed with water, and dried under vacuum at approx. 110 C. A
total of 11.868g of dried material was recovered. Upon heat
treatment at a maximum temperature of approx. 950 C in the presence
of (2%/98%) (v/v) H2/Ar atmosphere for 120 minutes, the sample lost
approximately 12.5% weight.
Example 15 (higher platinum content and platinum deposition
temperature)
[00350] Preparation of nominal 4%Pt8%Cu on activated carbon:
The following were added to a baffled beaker including approx. lOg
of activated carbon: 3.420g of CuS0405H20 solution, 9.375 g of
sucrose, 100g of degassed deionized water, and 9.675g of 50wt.%
NaOH. The mixture was heated to 30 C and stirred for 10 minutes
with a mechanical agitator. Then 3.331g of 37% formaldehyde was
added and the resulting slurry was heated to approx. 30-35 C,
followed by continued stirring for 90 minutes. Then the slurry
was filtered and washed once in the filter, and then re-slurried
in water to pH 1.97 by adding 1M degassed HC1. A solution of
0.964g of K2PtC14 in 20g of degassed water was then added to the
slurry, followed by continued stirring for 45 minutes at 45 C.
Then the slurry was heated to 60 C and stirred for an additional 45
minutes. The slurry was then filtered and washed with water, and
dried under a vacuum at approx. 110 C. A total of 12.283g of dried
material was recovered. Upon heat treatment to a maximum
temperature of approx. 950 C in the presence of a 2%/98% (v/v)
H2/Ar atmosphere for 120 minutes, the sample lost approximately
12.6% weight.
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Example 16 (one-pot recipe)
[00351] Preparation of nominal 2%Pt4%Cu on activated carbon:
The following were added to baffled beaker including 10g of
activated carbon: 1.644g of CuS0405H20 solution, 4.509 g of
sucrose, 90g of degassed deionized water, and 4.715g of 50 wt.%
NaOH. The mixture was heated to 30 C and stirred for 10 minutes
with a mechanical agitator. Then 1.736g of 37% formaldehyde was
added and the slurry was heated to approx. 30-35 C, followed by
continued stirring for 90 minutes. Then the slurry was acidified
to pH 2.98 by adding 1M degassed HC1. A solution of 0.454g of
K2PtC14 in 10g of degassed water was then added to the slurry,
followed by continued stirring for 60 minutes at ambient
conditions. Then the slurry was heated to 60 C and stirred for 30
more minutes. The slurry was then filtered and washed with water,
and dried under vacuum at approx. 110 C. A total of 11.864g of
dried material was recovered. Upon heat treatment at approx. 950 C
in the presence of a (2%/98%) (v/v) H2/Ar for 120 minutes, the
sample lost approximately 12.2% weight.
Example 17
[00352] Preparation of nominal 2%Pt4%Cu on activated carbon:
The following were added to a baffled beaker including 10g of
activated carbon: 1.645g of CuS0405H20 solution, 4.509 g of
sucrose, 90g of degassed deionized water, and 4.630g of 50wt.%
NaOH. The mixture was heated to 30 C and stirred for 10 minutes
with a mechanical agitator. Then 1.710g of 37% formaldehyde was
added and the slurry was heated to approx. 30-35 C, followed by
continued stirring for 90 minutes. Then the slurry was filtered
and washed once in the filter, and then re-slurried in water to pH
2.01 by adding 1M degassed HC1. A solution of 0.570g of H2PtC16 in
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15g of degassed water was then added to the slurry, followed by
continued stirring for 60 minutes at ambient conditions. Then the
slurry was heated to 60 C and stirred for an additional 30 minutes.
The slurry was then filtered and washed with water, and dried
under vacuum at approx. 110 C.
Example 18
[00353] Preparation of nominal 2%Pt/4%Cu on activated carbon:
The following were added to a baffled beaker including approx. 10g
of activated carbon: 1.644g of CuS0405H20 solution, 4.517 g of
sucrose, 70g of degassed deionized water, and 4.701g of 50wt.%
NaOH. The mixture was heated to 30 C and stirred for approx. 10
minutes with a mechanical agitator. Then 1.705g of 37%
formaldehyde diluted to 17.10g with degassed water was added, and
the slurry was heated at approx. 30-35 C, followed by continued
stirring for 60 minutes. Then the slurry was filtered and washed
once in the filter, and then re-slurried in water to pH 1.99 by
adding 1M degassed HC1. A solution of 0.460g of K2PtC14 in 10g of
degassed water was then added to the slurry, followed by continued
stirring for 60 minutes at ambient conditions. Then the slurry
was heated to 60 C and stirred for 30 more minutes. It was then
filtered and washed with water, and dried under vacuum at approx.
110 C. A total of 11.203g of dried material was recovered.
Example 19
[00354] This Example details surface area (SA) and CO
chemisorption analysis for catalysts of varying platinum and
copper contents prepared generally in accordance with the
conditions detailed herein in Example 7, and tested in PMIDA
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oxidation for 10 cycles generally under the conditions set forth
in Example 7.
MTC 6991.4
39 -21(53610)A/WO
125
Table 6
0
t..)
o
cycle
10 cycle o
10 cycle
spent spent
w
un
955 C-120 10 cycle 10 cycle 10 cycle 10 cycle
955 C-120 955 C-120
vl
(temp/time) 955 C-120 955 C-120 815 C-60
955 C-120 treated treated o
Average 2%Pt/ 396Pt/ 2%Pt/ 2.596Pt/ 2%Pt/
2%Pt/ 2%Pt/
Description C 3.45% Cu/C 6% Cu/C 3.45% Cu/C 7.5% Cu/C
4% Cu/C 4% Cu/C 3.75% Cu/C
Langmuir SA
(m2/g) 1499 1307 1208 1230 970 1236
1240 1254
t-plot micro SA
(m2/g) 1193 1065 984 1002 776 1019
1017 1034 0
o
K.)
Pore diameter
K.)
in
(A) 15.6 19.9 20.0 19.9 20.1 19.7
19.8 19.7 Fl.
w
Fl.
Meso-macro pore
K.)
SA (m2/g) 293.184 235.358 220.629 223.477 189.809 214.329
219.437 216.215 0
H
0
I
20-40 175.666 147.013 137.710 139.592 119.950 133.968
136.617 134.627 H
0
40-80 77.937 60.166 56.648 57.408 48.620 54.628
56.582 55.397 1
K.)
80-150 25.781 18.164 16.873 16.961 13.806 16.522
16.811 16.678
150-400 11.205 7.963 7.469 7.518 5.954 7.177
7.463 7.468
400-1000 2.159 1.736 1.630 1.685 1.251 1.672
1.8'6 1.680
1000-2000 0.396 0.315 0.297 0.313 0.228 0.331
8.23 0.315
2000-3000 0.04 0.001 0.002 0.000 0.000 0.031
. 0.050
Total meso-macro
IV
r)
pore SA (m2/7) 293.184 235.358 220.629 223.477 189.809
214.329 219.437 216.215
C4
w
Pt(0)[umol CO/g] NA 17.2 27.5 14.6 19.3
13.9 14.2 17.8 o
o
Total Pt
.6.
[mmol CO/g] NA 21.9 34.9 20 30.1 19.5
19.2 20.6 w
un
cA
w
MTC 6991.4
39-21(53610)A/WO
126
0
Table 7
t..)
o
o
,-,
cycle
10 cycle w
un
1-,
10 cycle
spent spent un
o
955 C-120 10 cycle 10 cycle 10 cycle 10
cycle 955 C-120 955 C-120
Pore
Average (temp/time) 955 C-120 955 C-120 815 C-60 955 C-
120 treated treated
diameter
C 2%Pt/ 3%Pt/ 2%Pt/ 2.5%Pt/ 2%Pt/
2%Pt/ 2%Pt/
(A) (31ots) 3.45% Cu/C 6% Cu/C 3.45%
Cu/C 7.5% Cu/C 4% Cu/C 4% Cu/C 3.75% Cu/C
<4.0 0.0541 0.0475 0.0475 0.0474 0 0.0478
0.0379 0.0476
4.0-4.6 0.1072 0.0853 0.0758 0.0759 0.0952 0.0765
0.0851 0.0856 n
4.7-5.2 0.063 0.0568 0.0473 0.0567 0.0471 0.0572
0.0565 0.0569 o
K.)
-3
5.3-6.0 0.063 0.0568 0.0566 0.0473 0.0356 0.0476
0.0472 0.0474 K.)
in
Fl.
6.1-7.1 0.0465 0.0369 0.0454 0.0459 0.0329 0.0462
0.0459 0.0458 w
Fl.
7.2-8.0 0.0346 0.0254 0.0241 0.0254 0.0239 0.0254
0.0331 0.025 K.)
0
H
8.1-9.0 0.0235 0.0224 0.0142 0.0221 0.0133 0.0226
0.0207 0.022 o
1
H
9.1-13.4 0.0589 0.0567 0.0538 0.0513 0.0424 0.0533
0.0498 0.0517 o
1
K.)
13.5-16.5 0.0216 0.017 0.016 0.0164 0.0129 0.0159
0.0196 0.0191 -3
16.6-21.4 0.0274 0.0241 0.0248 0.023 0.0211 0.024
0.0214 0.0212
21.5-27.0 0.0254 0.021 0.018 0.02 0.0156 0.0174
0.0179 0.0176
total
micropore
IV
volume
n
1-i
(cc/g) 0.5252 0.4499 0.4235 0.4314 0.34 0.4339
0.4351 0.4399
ci)
n.)
o
o
-a-,
.6.
t,..)
u,
c7,
t,..)
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[00355] Fig. 5C provides porosity data for each of the
catalysts tested.
Example 20
[00356] This example provides surface area (SA) and pore
volume (PV) analysis data for a carbon support treated by
contact with sucrose generally in accordance with the method
described below. Also provided are results for a nominal
2%Pt/3.45%Cu/C catalyst prepared using a carbon support treated
by contact with sucrose generally as described below, along with
copper and platinum deposition generally as described in Example
12. The metal impregnated support was not subjected to elevated
temperatures.
[00357] Carbon support (10 g) was added to a mixture
including degassed H20 (approx. 100 g), sucrose (approx. 3.8 g),
1M NaOH (approx. 6.15 g). To prepare the sucrose mixture, the
sucrose was first added to the water followed by addition of
NaOH, which was followed by addition of approx. 1.9 g of 37 wt.%
formaldehyde solution. After approximately 60 minutes at
approximately 25 C, the mixture was acidified to pH of
approximately 4.8 by addition of 2M HC1. The mixture was then
stirred for approximately 45 minutes at approximately 25 C, then
filtered to isolate the support and the support was dried for
approx. 10 hours in a vacuum oven at a temperature of approx.
110 C in the presence of nitrogen. Approx. 11.5 g of treated
support was recovered.
[00358] Both the catalyst and treated support were analyzed
by surface area and pore volume analyses generally as described
by Wan et al. in International Publication No. WO 2006/031938.
The surface area and pore volume analysis results are shown in
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Tables 8 and 9, respectively. Fig. 5D also provides the pore
volume results.
Table 8
Sucrose
adsorbed
Average Precursor, onto
Description Carbon 2%Pt/3.45%Cu/C Carbon
Langmuir SA (m2/g) 1499 957 954
t-plot micro pore SA
(m2/g) 1193 727 726
meso-macro pore SA
(m2/g) 293.184 222.314 219.061
20-40 175.666 136.964 133.600
40-80 77.937 58.165 58.144
80-150 25.781 17.608 17.651
150-400 11.205 7.676 7.743
400-1000 2.159 1.625 1.672
1000-2000 0.396 0.276 0.251
2000-3000 0.04 0.000 0.000
total meso-macro pore
SA (m2/g) 293.184 222.314 219.061
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Table 9
Pore Average Sucrose
diameter carbon Precursor, adsorbed onto
(A) (3 lots) 2%Pt/3.45%Cu/C carbon
<4.0 0.0541 0.0191 0.0193
4.0-4.6 0.1072 0.0478 0.0483
4.7-5.2 0.063 0.0381 0.0385
5.3-6.0 0.063 0.0475 0.0385
6.1-7.1 0.0465 0.0366 0.0464
7.2-8.0 0.0346 0.0243 0.0171
8.1-9.0 0.0235 0.0197 0.0222
9.1-13.4 0.0589 0.0443 0.0465
13.5-16.5 0.0216 0.0182 0.0149
16.6-21.4 0.0274 0.0207 0.0238
21.5-27.0 0.0254 0.018 0.0177
total
micro PV
(cc/g) 0.5252 0.3343 0.3332
[00359] As shown in these results, reductions in total
surface area, micropore surface area, and meso-/macropopre
surface were approx. equivalent for the catalyst in which
sucrose was present in the copper deposition bath, and for the
carbon support treated by contact with sucrose alone. Based on
these results, it is believed that a significant portion, if not
substantially all, of the surface area reduction for the
finished catalyst as compared to the starting support is based
on the presence of sucrose in the copper deposition bath.
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Example 21
[00360] This example details microscopy results for the
following samples:
(1) a carbon support having a total Langmuir surface of approx.
1500 m2/g (including micropore surface area of approx. 1200 m2/g
and meso-/macropore surface area of approx. 300 m2/g);
(2) the carbon support of (1) containing a nominal copper
content of approx. 3.45 wt.% deposited generally in accordance
with Example 12;
(3) a nominal 2%Pt/3.45%Cu/C catalyst including support (1) and
prepared generally as described in Example 12, but prior to
heating at elevated temperatures;
(4) the nominal 2%Pt/3.45%Cu/C catalyst of (3) after heating at
temperatures of approximately 950 C.
[00361] Microscopy analysis was generally conducted as
described in Example 46.
Carbon support
[00362] Fig. 6 is a STEM micrograph of the surface of the
carbon support.
Cu-impregnated support
[00363] Figs. 7 and 8 are STEM micrographs of the surface
of the Cu-impregnated support. These results indicate Cu
regions of irregular morphology and size deposited at the
surface of the carbon support.
Pt/Cu-impregnated support (prior to heat treatment)
[00364] Figs. 9-12 are micrographs of the surface of the
Pt/Cu impregnated support prior to treatment at elevated
temperatures. These results indicate regions of Cu deposited
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at the surface of the carbon support having Pt deposited thereon
that have generally retained the irregular morphology and size
of the deposited Cu regions.
[00365] Fig. 13 provides a STEM micrograph for a portion of
the impregnated support. The portion marked "Spectrum Image" was
subjected to line scan analysis, the results of which are shown
in Fig. 14. As shown, the line scan analysis indicates the
presence of copper and platinum throughout the Spectrum Image
portion.
Pt/Cu/C catalyst (after heating)
[00366] Fig. 15 is an STEM photomicrograph and Fig. 16 is a
high resolution TEM (HRTEM) photomicrograph of a portion of the
Pt/Cu/C catalyst after heating at elevated temperatures. These
Figs. indicate a change in the morphology of the Pt/Cu regions.
These results indicate formation of spherical particles of sizes
ranging from approx. 1 nm to approx. 15nm.
[00367] Figs. 17 and 18 are EDS spectra for particles of
varying sizes. As particle size increases, the atom ratio of
copper to platinum increases, indicating relatively constant
amount of platinum among of the particles. It is currently
believed that thickness of the platinum layer is relatively
constant over a range of particle size.
Pt/Cu/C catalyst used in 3 PMIDA reaction cycles
[00368] Figs. 19-21 are STEM photomicrographs for a portion
of a catalyst used in 3 PMIDA reaction cycles under the above-
noted conditions. These results indicate the presence of stable
particles of varying sizes, including those in the range of from
approx. 1-1.5 nm.
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[00369] Fig. 22 provides line scan data for the portion of
the catalyst surface marked "Spectrum Image" in Fig. 21. Based
on detection of Cu over the entire Spectrum Image, with the
highest copper content at the center of the particle while the
platinum signal remained relatively flat, these results suggest
the presence of a relatively thin outer platinum-containing
shell (i.e., no more than 3 atoms thick). That is, since the
line scan analysis utilized an X-ray beam of approx. 1 nm (10 A)
in size this suggests the presence of a platinum-containing
shell having a thickness of no more than 3 platinum atoms
(atomic size of platinum is 3A).
Pt/Cu/C catalyst used in 30 PMIDA reaction cycles
[00370] These results are for catalysts tested for 30
reaction cycles. The STEM photomicrographs of Figs. 23 and 24
indicate the presence of stable particles of varying sizes,
including approx. 1-1.5 nm. Fig. 25 provides line scan data for
the portion marked "Spectrum Image" in Fig. 24. These results
also indicate a relatively thin layer of platinum as both the
platinum and copper signals began to be detected at the same
point by the X-ray beam having a size of approx. 1 nm, again
indicating the presence of a platinum-containing shell less than
1 nm (i.e., less than 3 platinum atoms) thick.
[00371] Figs. 26 and 27 provide EDS spectra for particles
of approx. 2 nm and 9 nm in size. As shown, the atom percent of
copper increased significantly with particle size, including the
presence of a copper-rich core.
Example 22
[00372] This example details results of microscopy analysis
conducted generally as described in Example 46 for: (1) a
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nominal 2%Pt/3.45%Cu/C catalyst precursor prepared as described
in Example 9, and (2) a nominal 2%Pt/3.45%Cu/C catalyst prepared
from the precursor (1) (e.g., heating of the precursor to a
maximum temperature of approximately 950 C).
[00373] Figs. 28 and 29 are TEM and STEM images for
precursor (1). Figs. 30-37 provide TEM images and corresponding
line scan data for portions of the precursor surface. As shown
by the line scans, platinum and copper were detected throughout
the particle.
[00374] Figs. 38 and 39 are TEM and STEM images for
catalyst (2). Figs. 40 and 42 indicate the portion of the
catalyst surface analyzed by line scans, the results of which
are shown in Figs. 41 and 43, respectively. The line scan
results indicate the presence of platinum throughout the
particles.
Example 23
[00375] This example provides particle size distribution
analysis for a nominal 2%Pt/3.45%Cu/C catalyst prepared as
described in Example 9. Fifteen images of the type shown in
Figs. 44 and 45 were used for determining the size of a total of
1177 particles. The size distribution of the measured particles
is shown in Fig. 46. This example also provides particle size
distribution analysis for the catalyst after use in PMIDA
oxidation for 4 reaction cycles under the conditions described
in Example 7. Fourteen images of the type shown in Figs. 47 and
48 were used to determine the size of 1319 particles. The size
distribution of the measured particles is shown in Fig. 49.
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Example 24
[00376] This example provides X-ray diffraction results for
a nominal 2%Pt/3.45%Cu/C catalyst prepared as described in
Example 12.
[00377] Figs. 50 and 51 provide diffraction results for an
area of the catalyst surface having a diameter of approximately
1 m, measured using selected area electron diffraction (SAED).
Based on the generation of FCC (face centered cubic) indices
(i.e., the results denoted 113, 022, 002, and 111) and primitive
cubic indices (i.e., the results denoted 300, 221, 310, and
210), the SAED results indicate the presence of a CuPt alloy
phase (likely a Cu3Pt) alloy phase. The results may also
indicate the presence of a metallic copper phase.
[00378] Figs. 52 and 53 provide nanodiffraction results
from a single particle at the surface of the support. The
nanodiffraction results are obtained by focusing an X-ray beam
having a diameter of approximately 50 nm in diameter on a
portion of the catalyst surface. Based on the generation of
primitive cubic indices (i.e., 010, 100, and 01-1), these
results also indicate the presence of a CuPt alloy phase (likely
Cu3Pt). The indices denoted 200 and 11-1 are believed to be
evidence of the presence of a Cu phase, Pt phase, or further
evidence of a CuPt alloy phase. Figs. 54 and 55 highlight
nanodiffraction results (the circled portions) indicating the
presence of a metallic copper phase.
[00379] The following Examples 25-42 provide reaction
testing data for various catalysts prepared generally as
described in Examples 8-18. Various parameters (e.g., metal
loading, metal deposition temperature, and heat treatment
temperature) were modified to determine the effect, if any, on
catalyst performance. Unless specifically noted otherwise, the
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metal-impregnated support was heated to a maximum temperature of
approximately 955 C in the presence of a hydrogen (2%)/argon
atmosphere. The catalysts were generally tested in PMIDA
oxidation under the conditions set forth in Example 7.
Example 25
[00380] Catalysts: (1) 2.5%Pt/10%Cu; (2) 2.5%Pt/20%Cu; (3)
2.5%Pt/7.5%Cu; and (4) 5%Pt/0.1%Fe/0.4%Co. (nominal
compositions)
[00381] Fig. 56 provides cycle time data for each of (1)-
(4) for nine reaction cycles.
[00382] Fig. 57 provides platinum leaching data for (1) and
(2) for each of nine reaction cycles.
Example 26
[00383] Catalysts: (1) 2.5%Pt/7.5%Cu; (2) 2.5%Pt/5%Cu; (3)
5%Pt/0.1%Fe/0.4%Co; and (4) 720 C/2.5%Pt/10%Cu. (nominal
compositions)
[00384] Fig. 58 provides cycle time data for each of (1)-
(4) for nine reaction cycles.
Example 27
[00385] Catalysts: (1) 2.5%Pt/10%Cu and (2)
720 C/2.5%Pt/10%Cu. (nominal compositions)
[00386] Each catalyst was tested for 10 reaction cycles.
[00387] Fig. 59 provides cycle time data.
[00388] Fig. 60 provides IDA generation data.
[00389] Figs. 61 and 62 provide residual formaldehyde and
formic acid concentration, respectively.
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[00390] Table 10 provides a comparison of platinum leaching
for the two catalysts. As shown, less platinum was leached from
the catalyst prepared including heat treatment at 720 C.
Table 10
Pt/Parts per Million (ppm)
Cycle 2.5%Pt10%Cu 720 C-2.5%Pt10%Cu
1 0.103 <0.02
2
3 0.0715 <0.02
4
0.0539 <0.02
6
7 0.0514 <0.02
8
9 0.0507 0.0202
Example 28
[00391] Catalysts: (1) 2.5%Pt/7.5%Cu; (2)
815 C/2.5%Pt/7.5%Cu; and (3) 5%Pt/0.1%Fe/0.4%Co. (nominal
compositions) Each catalyst was tested for nine reaction cycles.
[00392] Fig. 63 provides cycle time data for each of (1)-
(3).
[00393] Figs. 64 and 65 provide residual formaldehyde and
formic acid concentration, respectively for each of (1)-(3).
Example 29
[00394] Catalysts: (1) 815 C/2.5%Pt/7.5%Cu; (2)
815 C/2.5%Pt/7.5%Cu; and (3) 5%Pt/0.1%Fe/0.4%Co. (nominal
compositions) Each catalyst was tested for nine reaction cycles.
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[00395] Fig. 66 provides cycle time data for each of (1)-
(3).
[00396] Figs. 67 and 68 provide residual formaldehyde and
formic acid concentration, respectively, for each of (1)-(3).
Example 30
[00397] Catalysts: (1) 815 C/2.5%Pt/7.5%Cu; (2)
815 C/2.5%Pt/5%Cu; (3) 5%Pt/0.1%Fe/0.4%Co; (4) 815 C/2.5%Pt/3%Cu.
(nominal compositions) Each catalyst was tested for ten reaction
cycles.
[00398] Fig. 69 provides IDA generation results for each of
(1)-(4).
[00399] Figs. 70 and 71 provide residual formaldehyde and
formic acid concentration, respectively, for each of (1)-(4).
Example 31
[00400] Catalysts: (1) 815 C/2.5%Pt/5%Cu; (2)
715 C/2.5%Pt/5%Cu; (3) 615 C/2.5%Pt/5%Cu; and (4)
5%Pt/0.1%Fe/0.4%Co. (nominal compositions) Each catalyst was
tested for ten reaction cycles and various parameters were
compiled for nine or each of the ten reaction cycles.
[00401] Fig. 72 provides cycle time results.
[00402] Figs. 73 and 74 provide residual formaldehyde and
formic acid concentrations, respectively.
[00403] Fig. 75 provides platinum leaching results.
[00404] Fig. 76 provides IDA generation results.
[00405] Fig. 77 provides NMG generation results.
[00406] Fig. 78 provides total CO2 generation results.
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Example 32
[00407] Catalysts: (1) 915 C/2%Pt/4%Cu (heated in a hydrogen
containing atmosphere, i.e., reduced); (2) 910 C/2%Pt/4%Cu
(heated in an inert atmosphere, i.e., calcined); and (3)
5%Pt/0.1%Fe/0.4%Co. (nominal compositions) Each catalyst was
tested for nine reaction cycles.
[00408] As shown in Fig. 79, cycle time was similar for
each of (1)-(3), but cycle time for catalyst (3) was slightly
higher for cycles 3 through 8.
[00409] Fig. 80 provides formaldehyde generation results.
[00410] Fig. 81 provides formic acid generation results.
[00411] As shown in Fig. 82, IDA generation was
substantially equivalent for each catalyst during cycles 3
through 9.
[00412] The results shown in Fig. 83 indicate reduced NMG
generation for each of the 2%Pt catalysts as compared to the
5%Pt catalyst.
[00413] Fig. 84 provides total CO2 generation results.
Example 33
[00414] This example provides platinum leaching results for
the following catalysts: (1) 815 C/2.5%Pt/5%Cu; (2)
815 C/2.5%Pt/3%Cu; (3) 910 C/2%Pt/4%Cu; (4) 908 C/2%Pt/3.6%Cu;
and (5) 975 C/2%Pt/3.6%Cu. (nominal compositions) The results
are shown in Fig. 85.
Example 34
[00415] This example provides testing results for catalysts
in which the temperature of copper deposition varied by approx.
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C (approx. 25 C and approx. 35 C) while the heat treatment
temperature after platinum deposition was substantially similar.
[00416] Catalysts: (1) 970 C/2%Pt/3.45%Cu/35 C and (2)
965 C/2%Pt/3.45%Cu/25 C. (nominal compositions)
[00417] As shown in Figs. 86 and 87, formaldehyde and
formic acid generation were slightly lower for the catalyst
prepared at the higher copper plating temperature.
[00418] The results shown in Fig. 88 indicate higher
initial IDA generation for the catalyst prepared at the higher
copper plating temperature, but similar results for each
catalyst beginning with the third cycle.
[00419] As shown in Fig. 89, platinum leaching was lower
for the catalyst prepared at the lower copper plating
temperature. And Fig. 90 indicates reduced initial copper
leaching for the catalyst prepared at the lower copper plating
temperature.
Example 35
[00420] This example provides results for extended PMIDA
oxidation testing over 30 reaction cycles.
[00421] The catalysts tested included:
(1) nominal 2%Pt/3.45%Cu/C prepared as described in Example 12;
(2) 5%Pt/0.1%Fe/0.4%Co;
(3) nominal 2%Pt/3.45%Ou/C prepared as described in Example 16;
(4) 5%Pt/0.5%Fe catalyst.
[00422] As shown in Figs. 91-94, the cycle time, total CO2
generation, formaldehyde generation, and formic acid generation
were substantially similar for each of (1)-(4). The catalyst
loading was constant for each catalyst; thus, catalysts (1) and
(3) provided similar results at reduced platinum loadings as
compared to catalysts (2) and (4).
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[00423] Fig. 95 provides Cu and Fe leaching data for
catalysts (1), (3), and (4).
Example 36
[00424] This example provides PMIDA oxidation testing
results for catalysts prepared at varying calcining temperatures
and having varying copper contents. Catalysts: (1)
908 C/2%Pt/3.6%Cu; (2)975 C/2%Pt/3.6%Cu; (3) 910 C/2%Pt/4%Cu; and
(4) 970 C/2%Pt/3.45%Cu. (nominal compositions)
[00425] Fig. 96 provides IDA generation results.
[00426] Figs. 97 and 98 indicate substantially similar
results for formaldehyde and formic acid generation.
Example 37
[00427] This example provides reactor testing data for
2%Pt/4%Cu/C catalysts prepared generally as described in Example
11. Each catalyst was tested over 9 PMIDA reaction cycles.
[00428] One catalyst was prepared by heating the metal-
impregnated support to a maximum temperature of approximately
950 C in the presence of an inert argon atmosphere. A second
catalyst was prepared by contacting the metal-impregnated
support to a maximum temperature of approximately 950 C in the
presence of a hydrogen/argon (2%/98%) (v/v) atmosphere.
[00429] Cycle time and CO2 generation data are provided for
the two catalysts in Table 11. Fig. 99 shows cycle time for
each catalyst.
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Table 11
Cycle Calcined Calcined H2-Reduced H2-Reduced
1 2220 38.75 1867 50.92
2 2226 37.67 2077 42.33
3 2181 37.58 2109 39.42
4 2181 38 2155 37.08
2179 37.25 2095 40.42
6 2094 39.25 2136 37.42
7 2078 39.75 2089 39
8 2075 39 2067 38.5
9 2034 40.33 2060 37.42
Example 38
[00430] This example provides reactor testing data for a
2%Pt/4%Cu/C catalyst and a 2%Pt/4%Cu/C metal-impregnated support
(precursor) prepared generally as described in Example 11. The
catalyst and metal-impregnated support were tested over 4 PMIDA
reaction cycles. The catalyst was prepared by contacting a
metal-impregnated support to a maximum temperature of
approximately 950 C in the presence of a hydrogen/argon (2%/98%)
(v/v) atmosphere.
[00431] Cycle time and CO2 generation data are provided for
the catalyst and metal-impregnated support in Table 12. Fig.
100 shows cycle time for each catalyst.
Table 12
Cycle Precursor Precursor Catalyst Catalyst
1 2003.4 36.92 1866.6 50.92
2 1912.5 39.17 2076.8 42.33
3 1841 41.58 2109.2 39.42
Example 39
[00432] This example provides a comparison of 2%Pt/4%Cu/C
catalysts prepared using different sources of platinum. Each
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catalyst was prepared generally as described in Example 11,
including heating of a metal-impregnated support to a maximum
temperature of approximately 950 C. Platinum was deposited by
displacement deposition onto copper-impregnated supports using
platinum sources of: (1) K2PtC14 (i.e., Pt+2 ions) and (2)
H2PtC1601-120 (i.e., Pt+4 ions).
[00433] Table 13 provides cycle time, CO2 generation data,
and difference in activity (based on cycle time) for each
catalyst over 9 reaction cycles. Figs. 101 and 102 provide
cycle time and activity difference data.
Table 13
Cycle K2PtC14 K2PtC14 H2PtC16 H2PtC16 delta t %
Activity
1 1866.6 50.92 1640.8 58.5 7.58 0.87
2 2076.8 42.33 1879.8 50.58 8.25 0.84
3 2109.2 39.42 1989.6 46.42 7 0.85
4 2155.1 37.08 1980.4 45.33 8.25 0.82
2095.1 40.42 1982 44.08 3.66 0.92
6 2135.9 37.42 1994.7 44.25 6.83 0.85
7 2089 39 1954.2 45.75 6.75 0.85
8 2066.8 38.5 1973.4 44.75 6.25 0.86
9 2059.6 37.42 1962.1 45.08 7.66 0.83
avg. 0.846
Total Cycle Total excluding the 5th
CO2 time CO2 Cycle time cycle
Example 40
[00434] This example provides CO chemisorption data (i.e.,
platinum site density) for catalysts of varying platinum content
prepared generally as described in Examples 8, 11, 14, and 15.
Table 14 provides the CO chemisorption (determined generally in
accordance with the method described in Example 67) and Fig. 103
provides a plot of platinum loading versus platinum site
density. The catalysts were tested in PMIDA oxidation for 10
reaction cycles prior to CO chemisorption analysis.
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Table 14
Chemisorption
Cycle 2
Pt site density
Pt loading ( mol CO/g catalyst)
2 20.24
2.5 30.1
3 34.9
4 58
[00435] These results show a linear relationship between
platinum loading and site density. Based on these results, it
is currently believed that a significant portion of the platinum
incorporated in the catalyst is present in the form of a
relatively thin shell. Conversely, a non-liner relationship
between platinum loading and site density has been observed for
conventional platinum-containing catalysts. This is currently
believed to be due to the fact that a greater portion of the
platinum is distributed throughout metal particles. Thus,
beyond certain level of platinum, loading platinum site density
does not increase since the portion of platinum distributed
throughout the particles does not contribute to exposed platinum
surface area.
Example 41
[00436] Catalysts containing nominal metal contents of
approximately 2%Pt and 4%Cu were prepared generally as described
in Examples 11 and 12. The metal deposition bath was maintained
under a nitrogen atmosphere during copper deposition. Reaction
testing results comparing the Pt/Cu catalysts to a 5%Pt/0.5% Fe
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catalyst are shown in Fig. 104. As shown, all catalysts
provided comparable activity.
Example 42
[00437] This example details reaction testing of nominal
3%Pt/6%Cu catalysts prepared as described in Example 14 at
varying catalyst loadings. One catalyst was tested at a
catalyst loading of approximately 0.25 g and another was tested
at a loading of approximately 0.17 g. The performance of each
catalyst was compared to a 5%Pt/0.5%Fe catalyst prepared
generally as described in U.S. Patent No. 6,417,133 at a loading
of 0.25 g. Total catalyst and platinum loadings are summarized
in Table 15. Total CO2 generation results and cycle time
results are shown in Figs. 105 and 106, respectively. As
compared to the 5%Pt/0.5%Fe catalyst, these results indicate
improved activity for the 3%Pt catalyst at equivalent catalyst
loading and at least comparable activity at reduced catalyst
loading. Accordingly, 3%Pt catalysts of the present invention,
or other similar catalysts, may be utilized to provide an
improvement in catalyst activity, or a reduction in working
metal capital.
Table 15
Cat. Loading Reduction Pt loading Reduction in
Pt loading
Condition One 0.25 g 0% 0.0075 g 40%
Condition Two 0.167 g 33% 0.005 g 60%
Control 0.25 g 0% 0.0125 g 0%
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III. Additional Embodiments
Disodiumiminodiacetic acid (DSIDA) Preparation
Example 43
[00438] This example details analysis and testing of: (1) a
carbon-supported palladium and copper-containing catalyst
(CuPdC) of the type described in U.S. Patent No. 5,916,840,
5,689,000, and/or 5,627,125; and (2) a CuPdC catalyst prepared
as described in U.S. Patent No. 5,916,840, 5,689,000, and/or
5,627,125 that was treated by contact with a mixture containing
1,4-cyclohexane dione and ethylene glycol as described in
Example 1 (mechanism 2).
[00439] The treated and un-treated catalysts were analyzed
to determine their Langmuir surface areas and to provide
comparisons of the micropore and macropore surface areas prior
to and after treatment.
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Table 16
% of original % of original
Sample Diane Dial micropore SA macropore SA
1,4- Ethylene
Carbon A disubstituted Glycol 22.6 75.8
1,3- Ethylene
Carbon A disubstituted Glycol 58.4 84
1,4- Ethylene
Carbon B disubstituted Glycol 55.6 78.7
1,3- Ethylene
Carbon B disubstituted Glycol 32.2 39.8
1,4- Ethylene
Carbon C disubstituted Glycol 17.9 76.8
1,3- Ethylene
Carbon C disubstituted Glycol 45 75.6
1,4- 1,2-
Carbon C disubstituted Propanediol 14.4 67.5
1,3- 1,2-
Carbon C disubstituted Propanediol 56.1 80.7
[00440] As shown in Table 16, treatment of the catalyst
provided a 75% reduction in micropore surface area of the
catalyst, while providing a reduction in macropore surface area
of less than 20% (i.e., a preferential reduction in micropore
surface area approximately 4 times greater than the reduction in
macropore surface area).
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[00441] The treated and untreated catalysts were also
tested for the conversion of diethanolamine to
disodiumiminodiacetic acid. Mixtures including water, the
(original or modified) catalyst (2 wt.%), diethanolamine (1.8
wt.%), sodium hydroxide (2.4 wt.%), and disodiumiminodiacetic
acid (DSIDA) (12.5 wt.%) were heated to temperatures ranging
from 150-160 C over the course of 5 hours and under a pressure
of approximately 135 psig. These conditions were selected to
determine the performance of the modified and unmodified
catalysts with regard to oxalate and glycine formation. The
results are shown in Fig. 107. The modified catalyst provided
an approximately 8-10 fold reduction in oxalate formation and an
approximately 4 fold reduction in glycine generation. These
results suggest that the modified catalyst provided reduced
exposed noble metal believed to contribute to glycine and
oxalate formation.
Example 44
[00442] This example details testing of palladium and
copper-containing carbon-supported (CuPdC) catalysts in
preparation of DSIDA by dehydrogenation of DEA. The catalysts
were prepared as described in U.S. Patent No. 5,916,840,
5,689,000, and/or 5,627,125 and tested generally under the
conditions described therein. Two CuPdC catalysts were prepared
generally in accordance with the method described in one or more
of these patents. Each catalyst was prepared to include 24wt.%
Cu. One catalyst was prepared using an untreated carbon
support; this resulted in a catalyst including 3wt.%Pd (i.e.,
24%Cu/3%Pd/C). The second catalyst was prepared using a carbon
support treated by the present method as described in Example 1
by contact with 1,4-CHDM; this resulted in a catalyst including
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approx. 2.4wt.% Pd (i.e., 24%Cu/2.4%Pd/C). Thus, it is believed
that use of the modified support resulted in reduced palladium
deposition.
[00443] Each catalyst was tested in conversion of DEA to
DSIDA generally in accordance with the conditions set forth in
U.S. Patent No. 5,916,840, 5,689,000, and/or 5,627,125. The
results are shown in Fig. 108 and Table 17.
[00444] As shown in Fig. 108, beginning with the second
cycle, cycle time was reduced for the catalyst including 2.4% Pd
on the treated carbon support. That is, the catalyst prepared
using the treated carbon support provided an increase in
activity of approx. 15-20% at a lower noble metal content.
Table 17
24%Cu on 2.4%Pd/
Cycle modified MC-10 24%Cu on 3%Pd/MC-10
Oxalic Hydroxyethyl Oxalic
mol % GlycineAcid Glycine Glycine Acid Hydroxyethyl Glycine
1 1.08 0.49 0.46 1.69 0.73 0.56
2 0.9 0.38 0.46 1.28 0.45 0.42
3 0.88 0.35 0.49 1.22 0.44 0.43
4 0.9 0.34 0.58 1.3 0.43 0.4
0.9 0.34 1.01 1.25 0.42 0.42
6 0.94 0.34 0.87 1.31 0.44 0.41
7 0.96 0.34 0.89 1.3 0.43 0.39
8 0.97 0.34 0.76 1.35 0.43 0.36
9 1.01 0.34 0.71 1.35 0.43 0.38
1.01 0.35 0.61 1.38 0.43 0.36
[00445] As shown in Table 17, use of the 2.4%Pd catalyst on
the modified carbon support provided reduced oxalic acid
generation and glycine generation as compared to the 3%Pd
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catalyst on the unmodified carbon support (e.g., an improvement
in oxalic acid and glycine selectivities of approx. 15% and 25%,
respectively).
IV. Platinum-Iron
Example 45
[00446] This example details preparation of a catalyst
having a nominal platinum content of 2 wt.% and a nominal iron
content of 4 wt.% on an activated carbon support having a
Langmuir surface area of approximately 1500 m2/g. The following
preparation was conducted under nitrogen protection.
[00447] Activated carbon (approximately 10.458 g) and
degassed water (approximately 90 g) were mixed in a baffled
beaker under a nitrogen atmosphere. FeC130xH20 (2.007 g) was
dissolved in degassed water (40 g) and this solution was pumped
into the baffled beaker over a period of one hour. The pH of
the slurry within the baffled beaker was maintained at 4 by
introduction of 2.5N degassed NaOH, as necessary. After
addition of the FeC13 solution was completed, the pH of the
slurry was raised to approximately 4.5 and the slurry was
allowed to mix at room temperature for approximately 15 minutes.
The slurry was then heated to a temperature of approximately
60 C over a period of approximately 48 minutes, during which
time the pH of the slurry was maintained at approximately 4.5 by
addition of 2.5N NaOH.
[00448] The pH of the slurry was then raised to
approximately 10.5 over a period of approximately 30 minutes at
a temperature of approximately 60 C, and at a rate of 0.5 pH
units per 5 minutes. After pH adjustment, the slurry was
allowed to mix for approximately 10 minutes.
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[00449] Sodium borohydride (NaBH4) (approximately 0.686 g)
was dissolved in degassed water (approximately 20 g); seven
drops of 2.5N degassed NaOH were added to stabilize the NaBH4
solution, and the resulting NaBH4 solution was introduced to the
baffled beaker at approximately 60 C over a period of 20
minutes. The slurry was then allowed to mix for ten additional
minutes at approximately 60 C. The slurry was then filtered and
the wet cake was then re-slurried in the baffled beaker in
degassed deionized water (approx. 90 g). The pH of the
resulting slurry was then lowered to approximately 5 by
introduction of degassed 2M HC1.
[00450] K2PtC14 (approximately 0.456 g) was dissolved in
degassed water (approximately 20 g) and the resulting Pt
solution was then added to the baffled beaker over a period of
three minutes. The resulting slurry was then allowed to mix at
ambient conditions (approximately 22 C) for approximately 60
minutes, and then heated to a final temperature of 65 C over a
period of 30 minutes, and then allowed to mix at 60 C. The
resulting slurry was then filtered and washed twice by contact
with degassed water (approximately 100 g) at a temperature of
approximately 65 C. The washed sample was then dried in a
vacuum oven at approximately 110 C for approximately 12 hours
with a small nitrogen stream to form a Pt/Fe catalyst precursor.
[00451] The catalyst precursor was then heated at elevated
temperatures up to approximately 900 C in the presence of a
hydrogen/argon stream (2%/98%; v/v) for approximately 120
minutes.
[00452] The 2%Pt/4%Fe finished catalyst was tested in PMIDA
oxidation under the conditions set forth in Example 7.
Inductively Coupled Plasma (ICP) analysis was used to determine
platinum and iron leached from the catalyst and present in the
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151
reaction mixture. ICP was conducted using a VG PQ ExCell
Inductively Coupled Plasma-Mass Spectrometer (ICP-
MS) (commercially available from Thermo Jarrell Ash Corp., Thermo
Elemental, Franklin, MA). The results are set forth in Table
18.
[00453] Fig. 109 provides results of XRD analysis
(conducted as set forth in Example 69) for the finished catalyst
(i.e., before reactor testing).
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39-21(53610)A/WO
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Table 18
0
Cycle 1 2 3 4 5 6
7 8 9 10 t-.)
=
=
Total CO2 (cc) 1766.6 1871.4 1966.5 1946.8 1935.5
1957.5 1940.7 1947.9 1932.0 1600.6
1-,
w
un
End point(min) 45.00 39.75 38.08 39.92 40.25
38.83 39.25 40.00 39.83 40.00
un
=
Maximum CO2
Concentration
(%) 35.7 37.9 38.8 36.9 36.7
37.4 37.0 36.7 36.5 36.5
PMIDA (wt.%) 0.008 0.010 0.010
0.010 0.010 0.034
Glyphosate(wt.%) 5.293 5.378 5.400
5.393 5.392 5.563 n
IDA(wt.%) 0.099 0.065 0.051
0.045 0.040 0.039 0
1.)
-.3
"
CH20 (PPm) 2421 1990 1838
1660 1737 2309 LT'
a,
w
a,
HCOOH(ppm) 6696 6555 6143
6220 5716 6635 1.)
0
Pt(ppm) <0.01 <0.01 <0.01
<0.01 <0.01 <0.01 H
0
I
H
Fe(ppm) 1.484 0.494 <0.1
<0.1 <0.1 <0.1 0
1
1.)
-.3
Iv
n
,-i
cp
w
=
=
-a
.6.
w
u,
c,
w
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Example 46
[00454] This example details preparation of a catalyst
having a nominal platinum content of 2 wt.% and a nominal iron
content of 4 wt.% on an activated carbon support having a
Langmuir surface area of approximately 1500 m2/g. The following
preparation was conducted under nitrogen protection.
[00455] Activated carbon (approximately 10.455 g) and
degassed water (approximately 90 g) were mixed in a baffled
beaker under a nitrogen atmosphere. Fe2(SO4)30xH20 (2.990 g) was
dissolved in degassed water (40 g) and this solution was pumped
into the baffled beaker over a period of one hour. The pH of
the slurry within the baffled beaker was maintained at 4 by
introduction of 2.5N degassed NaOH, as necessary.
[00456] Mixing of the components of the slurry within the
baffled beaker occurred for a total of approximately 20 minutes
at a pH of approximately 4. The pH of the slurry was then
raised to 4.5 by addition of NaOH. The slurry was then heated
to a temperature of approximately 60 C over a period of 30
minutes. During the heating, the pH was maintained at 4.5 by
introduction of 2.5N degassed NaOH (as necessary). At this
elevated temperature, the pH of the slurry was raised to
approximately 6.5 over a period of 20 minutes, via increases in
pH at a rate of approximately 0.5 pH units per 5 minutes.
[00457] Sodium borohydride (NaBH4) (approximately 0.681 g)
was dissolved in degassed water (approximately 20 g) and then
pumped into the baffled beaker at approximately 60 C over a
period of 20 minutes. The slurry was then allowed to mix for ten
additional minutes at 60 C. The slurry was then allowed to cool
to 45 C, and then filtered. The wet cake was then re-slurried in
the baffled beaker in degassed deionized water (90 g). The pH
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of the resulting slurry was then lowered to approximately 5 by
introduction of degassed 2M HC1.
[00458] K2PtC14 (approximately 0.460g) was dissolved in
degassed water (approximately 20g) and the resulting Pt solution
was then added to the baffled beaker over a period of five
minutes. The resulting slurry was then allowed to mix under
ambient conditions (approximately 22 C) for approximately 60
minutes, and then heated to a final temperature of 65 C over a
period of 30 minutes, and then allowed to mix at 65 C for an
additional 10 minutes. The resulting slurry was then filtered
and washed twice by contact with degassed water (approximately
100g) at a temperature of approximately 65 C. The washed sample
was then dried in a vacuum oven at approximately 110 C for
approximately 12 hours with a small nitrogen stream to form a
Pt/Fe catalyst precursor.
[00459] The catalyst precursor was then heated at elevated
temperatures up to approximately 900 C in the presence of a
hydrogen/argon stream (2%/98%; v/v) for approximately 120
minutes.
[00460] Table 19 sets forth PMIDA reaction testing results,
platinum leaching data, and iron leaching data for the 2%Pt/4%Fe
finished catalyst.
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39-21(53610)A/WO
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Table 19
0
Cycle 1 2 3 4 5 6
7 8 9 10
o
o
Total CO2 (cc) 1912.0 1933.8 1951.2 1978.7 1944.0
1943.9 1956.3 1891.4 1864.9 1602.2
1-,
w
End point(min) 38.17 37.33 36.75 35.67 37.75 37.50
37.67 39.50 40.83 40.17 un
1-,
un
o
Maximum CO2
Concentration
(%) 40.5 39.6 39.9 41.3 38.8 39.6
39.0 37.8 36.7 37.2
PMIDA (wt.%) ND 0.006 0.006
0.007 0.007 0.009
Glyphosate(wt.%) 5.184 5.249 5.382
5.349 5.393 5.497
n
IDA(wt.%) 0.139 0.055 0.040
0.038 0.032 0.032
o
CH2O(PPm) 2586 2212 2203
2149 2300 2983 "
-.3
N)
HCOOH(ppm) 5387 5525 6021
5843 5623 5958 in
.1.
w
.1.
Pt(ppm) 0.019 0.024 0.027
0.025 0.027 0.032
1.)
o
Fe(ppm) 16.420 0.629 0.222
0.077 <0.05 <0.05
I
H
0
I
KJ
---]
,-o
n
,-i
cp
t..,
,4z
7:-:--,
.6.
t..,
u,
cA
t..,
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Example 47
[00461] This Example provides the results of X-Ray
Diffraction (XRD) analysis for the catalyst prepared as
described in Example 46. XRD analysis was conducted as set
forth in Example 69.
[00462] The results are shown in Figs. 110 and 111. These
results indicate the presence of Fe3Pt bimetallic alloy.
Example 48
[00463] This example details preparation of a catalyst
having a nominal Pt content of 2 wt.% and a nominal iron content
of 4 wt.% on an activated carbon support having a Langmuir
surface area of approximately 1500 m2/g. The following
preparation was conducted under nitrogen protection.
[00464] Activated carbon (approximately 10.455 g) and
degassed water (approximately 90 g) were mixed in a baffled
beaker under a nitrogen atmosphere.
[00465] FeC1306H20 (approximately 2.009g) was dissolved in
degassed water (40 g) and this solution was pumped into the
baffled beaker over a period of one hour. The pH of the slurry
within the baffled beaker was maintained at 4 by introduction of
2.5N degassed NaOH, as necessary. After addition of the
FeC1306H20 solution to the beaker was completed, the pH of the
slurry was raised to approximately 4.5 by addition of NaOH and
the slurry was allowed to mix at ambient conditions
(approximately 22 C) for approximately 20 minutes.
[00466] The slurry was then heated to a temperature of
approximately 60 C over a period of approximately 50 minutes.
During the heating, the pH was maintained at 4.5 with addition
of 2.5N degassed NaOH. At this elevated temperature, the pH of
the slurry was raised to approximately 10.5 over a period of 30
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157
minutes, via increases in pH at a rate of approximately 0.5 pH
units per 5 minutes.
[00467] Sodium borohydride (NaBH4) (approximately 0.69 g)
was dissolved in degassed water (approximately 20 g); 7 drops of
2.5N NaOH was added to stabilize the NaBH4 solution. The sodium
borohydride solution was then pumped into the baffled beaker at
approximately 60 C over a period of 20 minutes. The slurry was
then filtered and the wet cake was then re-slurried in the
baffled beaker in degassed deionized water (90 g). The pH of
the resulting slurry was then lowered to approximately 5 by
introduction of degassed 2M HC1.
[00468] K2PtC14 (approximately 0.460 g) was dissolved in
degassed water (approximately 20 g) and the resulting Pt
solution was then added to the baffled beaker over a period of
three minutes. The resulting slurry was then allowed to mix at
ambient conditions (approximately 22 C) for approximately 60
minutes, and then heated to a final temperature of approximately
65 C.
[00469] The resulting slurry was then filtered and washed
twice by contact with degassed water (approximately 100 g) at a
temperature of approximately 65 C. The washed sample was then
dried in a vacuum oven at approximately 110 C for approximately
12 hours with a small nitrogen stream to form a Pt/Fe catalyst
precursor.
[00470] The catalyst precursor was then heated at elevated
temperatures up to approximately 900 C in the presence of a
hydrogen/argon stream (2%/98%; v/v) for approximately 120
minutes.
[00471] Table 20 sets forth PMIDA reaction testing results,
platinum leaching data, and iron leaching data for the 2%Pt/4%Fe
finished catalyst.
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39-21(53610)A/WO
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Table 20
0
Cycle 1 2 3 4 5
6 7 8 9 t..)
o
o
Total CO2 (cc) 1738.2 1826.0 1846.2 1857.1 1866.1
1872.0 1878.0 1862.4 1875.6 1(
1-,
w
End point(min) 46.75 42.50 42.08 41.67 41.50
41.58 41.50 42.25 42.00 , un
1-,
un
o
Maximum CO2
Concentration
(%) 34.4 35.3 35.6 35.7 35.7
35.6 35.9 35.3 35.4 ........,
PMIDA (wt.%) 0.007 0.010 0.009
0.009 0.009 0.060
Glyphosate(wt.%) 5.339 5.371 5.441
5.389 5.298 5.245
n
IDA(wt.%) 0.083 0.054 0.046
0.045 0.042 0.041
0
CH20(1010m) 2158 1857 1669
1706 1682 1831 "
-.3
N)
HCOOH(ppm) 7454 7161 6919
6648 6487 6941 in
.1.
w
.1.
Pt(ppm) 0.011 0.013 0.015
0.015 0.015 0.019
1.)
0
Fe(ppm) 3.114 0.543 0.178
0.124 0.053 0.062
I
H
0
I
KJ
---]
Cycle 11 12 13 14 15 16
17 18 19 20 21
Total CO2 (cc) 1875.8 1868.2 1878.2 1868.5 1855.9
1890.5 1872.9 1837.5 1854.1 1845.7 1830.5
End point(min) 41.33 42.33 42.25 42.67 43.58 42.08
43.83 44.33 44.25 44.25 45.25
IV
Maximum CO2
n
,-i
Concentration
cp
(%) 35.7 35.9 35.5 35.0 34.6 35.5
34.4 34.1 34.1 34.4 33.9a'
_______________________________________________________________________________
__________________________________________ o
PMIDA (wt.%) 0.009 0.010 0.009
0.010 0.010 0.010 0.010'-g-
_______________________________________________________________________________
__________________________________________ .6.
w
Glyphosate(wt.%) 5.315 5.405 5.406
5.382 5.371 5.477 5.424u4
cA
_______________________________________________________________________________
__________________________________________ w
IDA(wt.%) 0.043 0.041 0.038
0.039 0.037 0.036 0.037
CH20 (PPm) 1898 2086 2067
2111 2173 2107 1853
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39-21(53610)A/WO
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HCOOH(ppm) 6159 6287 6199
6302 5805 6582
-1
0
Pt(ppm) 0.023 0.024 0.024
0.023 0.024 0.024 w
o
Fe(ppm) <0.05 <0.05 0.054
<0.05 <0.05 <0.05 <C o
o
1-,
un
1-,
un
o
0
0
1.)
-3
N)
ul
.1.
w
.1.
1.)
0
H
0
I
H
0
I
KJ
---]
,-o
n
,-i
cp
t..,
,4z
7:-:--,
.6.
t..,
u,
cA
t..,
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[00472] Fig. 111A includes platinum leaching data for the
catalysts of Examples 46 and 48, as compared to a (Reference)
5%Pt/0.5%Fe catalyst prepared as described by Wan et al. in
International Publication No. WO 2006/031938.
Example 49
[00473] The following preparation was conducted under
nitrogen protection.
[00474] Activated carbon (approximately 10.456 g) and
degassed water (approximately 90 g) were placed in a baffled
beaker and allowed to mix for 20 minutes. FeC1306H20 (2.009 g)
was dissolved in degassed water (approx. 40 g) and this solution
was pumped into the baffled beaker over a period of 30 minutes
while the pH of the slurry was maintained at 4 by addition of
2.5N NaOH. After addition of the FeC1306H20 solution, the pH was
raised to 4.5 and allowed to mix for 10 minutes. The slurry was
then heated to approximately 50 C over a period of 30 minutes,
while the pH was maintained at pH 4.5. The pH of the slurry was
then raised to 8 over a period of 15 minutes, and allowed to mix
for approximately 10 minutes. Ethylene glycol (approx. 1.386 g)
was then added to the slurry, and allowed to mix at
approximately 60 C for approximately 20 minutes. After mixing
was complete, the slurry was allowed to cool to 30 C.
[00475] The pH of the solution was then lowered to 5 by
addition of 0.5M degassed HC1. K2PtC14 (0.460 g) was dissolved
in degassed water (20 g). The Pt solution was then added to the
baffled beaker over a period of three minutes. The slurry was
then allowed to mix at ambient conditions (approximately 22 C)
room temperature for 30 minutes, and then heated to a
temperature of 60 C over a period of 10 minutes.
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[00476] The slurry was then filtered, and the wet cake was
hot washed twice at 60 C with approximately 100 mL of degassed
water. The resulting sample was then dried in a vacuum oven at
110 C for 12 hours with a small nitrogen stream.
Example 50
[00477] The following preparation was conducted under
nitrogen protection.
[00478] Activated carbon (10.456 g) and degassed water
(approximately 90 g) were placed in a baffled beaker and allowed
to mix for 20 minutes. FeC1306H20 (2.011 g) was dissolved in
degassed water (approximately 40 g) and this solution was pumped
into the baffled beaker over a period of 34 minutes while the pH
of the slurry was maintained at 4 by addition of 2.5N NaOH.
[00479] Upon the complete addition of the FeC1306H20
solution, the pH was raised to 4.5, and allowed to mix for 10
minutes. The slurry was then heated to approximately 60 C over
a period of 34 minutes, while the pH was maintained at 4.5. The
pH of the slurry was then raised to 11 over a period of 30
minutes, and then allowed to mix for 10 minutes. Ethylene
glycol (1.385 g) was then added to the slurry, and allowed to
mix at 60 C for approximately 10 minutes.
[00480] The pH of the solution was then lowered to 5 by
addition of 1M degassed HC1. K2PtC14 (0.459 g) was dissolved in
degassed water (20 g). The Pt solution was then added to the
baffled beaker over a period of three minutes. The slurry was
then allowed to mix at ambient conditions (approximately 22 C)
for 30 minutes, and then heated to a temperature of
approximately 60 C over a period of 10 minutes.
[00481] The slurry was then filtered, and the wet cake was
hot washed twice at 60 C with approximately 100 ml of degassed
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water. The resulting sample was then dried in a vacuum oven at
110 C for 12 hours with a small nitrogen stream.
[00482] Four 2%Pt/4%Fe catalysts were prepared from a
precursor prepared as described that was heated at elevated
temperatures in the presence of a hydrogen/argon stream (4%/96%;
v/v) for approximately 120 minutes. Maximum heating
temperatures were:
(1) 900 C;
(2) 750 C;
(3) 650 C;
(4) 550 C.
[00483] Fig. 112 provides results of XRD analysis of
catalyst (1); these results indicate the presence of a Fe3Pt
phase.
[00484] Fig. 113 provides results of XRD analysis of
catalyst (2); these results indicate the presence of a Fe3Pt
phase.
[00485] Fig. 114 provides results of XRD analysis of
catalyst (3); these results indicate the presence of a Fe3Pt
phase.
[00486] Fig. 115 provides results of XRD analysis of
catalyst (4); these results indicate the presence of a FePt
phase.
[00487] Reaction testing data, platinum leaching data, and
iron leaching data for the 900 C/2%Pt/4%Fe catalyst are set
forth in Table 21.
MTC 6991.4
39-21(53610)A/WO
163
Table 21
0
Cycle 1 2 3 4 5
6 7 8 n.)
o
o
Total CO2 (cc) 1751.9 1793.3 1863.9 1930.6 1931.1
1946.4 1926.7 1602.3
c'7'a
un
End point(min) 44.08 43.00 41.67 40.75 41.00
41.25 41.08 42.90 ''cll
=
Maximum CO2
Concentration
(%) 36.2 35.2 35.3 35.5 35.7
35.2 36.1 34.4
PMIDA (wt.%) 0.003 0.006 0.006
0.006 0.104
Glyphosate(wt.%) 5.243 5.398 5.486
5.376 5.539 n
IDA(wt.%) 0.079 0.040 0.035
0.034 0.032 0
I.)
..A
CH20(PPm) 3032 2513 2072
2156 2596 "
cy.
a,.
w
HCOOH(ppm) 6300 6615 6554
6358 6488
I.)
Pt(ppm) 0.011 0.014 0.014
0.013 0.017 0
H
0
1
Fe(ppm) 24.050 3.309 0.494
0.462 0.409 H
1
I.)
..A
1-d
n
,-i
cp
t..,
'a
.6.
t..,
u,
cA
t..,
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164
[00488] Reaction testing data, platinum leaching data, and
iron leaching data for the 750 C/2%Pt/4%Fe catalyst are set forth
in Table 22.
MTC 6991.4
39-21 (53610)A/WO
165
0
Table 22
w
o
o
Cycle 1 2 3 4 5 6
7 8 9
W"
un
Total CO2 (cc) 1812.9 1786.8 1854.8 1901.3 1864.6
1906.0 1921.1 1913.3 1601.9 'cil
o
End point(min) 39.92 42.58 41.42 40.25 42.58 41.83
41.50 42.00 42.55
Maximum CO2
Concentration
(%) 39.2 35.8 35.7 36.3 34.5 34.9
35.6 35.0 35.2
PMIDA (wt.%) ND 0.009 0.006
0.010 0.064 n
Glyphosate(wt.%) 5.275 5.357 5.464
5.471 5.528 0
I.)
-3
IDA(wt.%) 0.098 0.037 0.033
0.035 0.030 I\)
ul
a,
w
cH20 (ppm) 2901 2398 2105
2010 2550 a,
I.)
o
HCOOH (ppm) 6151 6628 6634
6640 6553 H
0
I
Pt(ppm) 0.013 0.015 0.016
0.016 0.019 H
0
I
KJ
Fe(ppm) 24.870 3.516 0.686
0.476 0.356 -3
Iv
n
,-i
cp
t..,
'a
.6.
t..,
u,
cA
t..,
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166
[00489] Reaction testing data, platinum leaching data, and
iron leaching data for the 650 C/2%Pt/4%Fe catalyst are set
forth in Table 23.
MTC 6991.4
39-21 (53610)A/WO
167
Table 23
0
Cycle 1 2 3 4 5 6
7 8 9 10 t-.)
o
o
Total CO2 (cc) 1782.0 1849.5 1908.8 1897.5 1957.4
1947.6 1878.0 1901.6 1913.4 1602.7
1-,
w
un
End point(min) 41.42 40.67 39.33 39.75 39.08 38.00
42.25 41.50 41.08 42.23
un
o
Maximum CO2
Concentration
(%) 38.7 36.7 37.2 36.8 37.7 39.7
34.9 35.5 36.1 35.3
PMIDA (wt.%) ND 0.005 0.006
0.005 0.005 0.067
Glyphosate(wt.%) 5.229 5.373 5.394
5.413 5.394 5.490 n
IDA(wt.%) 0.099 0.045 0.040
0.037 0.036 0.036 o
1.)
-.3
CH20(PPm) 3042 2485 2357
2358 2395 2754 "
LT'
a,
w
HCOOH (ppm) 6185 6634 6461
6521 6372 6512 a,
1.)
Pt(ppm) 0.014 0.016 0.015
0.015 0.015 0.019 o
H
o
1
Fe(ppm) 25.230 2.754 0.493
0.395 0.422 0.332 H
0
I
N
-.I
IV
n
,-i
cp
t..,
,.z
'a
.6.
t..,
u,
cA
t..,
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168
[00490] Reaction testing data, platinum leaching data, and
iron leaching data for the 550 C/2%Pt/4%Fe catalyst are set
forth in Table 24.
MTC 6991.4
39-21(53610)A/WO
169
Table 24
0
Cycle 1 2 3 4 5 6
7 8 9 t..)
o
o
o
Total CO2 (cc) 1834.2 1842.8 1885.9 1881.2 1876.2
1891.8 1887.9 1842.3 1839.5
c'7'a
vi
End point(min) 38.17 39.58 38.58 39.08 40.25
39.67 40.17 42.00 42.08
o
Maximum CO2
Concentration
(%) 41.0 38.1 38.6 38.0 36.7
37.5 37.3 35.8 35.8
PMIDA (wt.%) 0.003 0.007 0.006
0.007 0.009
Glyphosate(wt.%) 5.197 5.376 5.379
5.339 5.341 0
0
IDA(wt.%) 0.095 0.049 0.044
0.041 0.037 "
-3
I.)
in
a2() (PPm) 2670 2306 2018
2236 2425
w
a,
HCOOH(ppm) 6221 7076 7141
7100 7033 I0)
H
0
Pt(ppm) 0.015 0.015 0.015
0.016 0.016 '
H
0
I
Fe(ppm) 27.940 2.972 0.594
0.315 0.406 "
-3
Iv
n
,-i
cp
w
.6.
w
u,
cA
w
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Example 51
[00491] The following preparation was conducted under
nitrogen protection.
[00492] Activated carbon (approximately 10.456 g) and
degassed water (approx. 90 g) were placed in a baffled beaker
and allowed to mix for approximately 20 minutes.
[00493] FeC1306H20 (2.009 g) was dissolved in degassed water
(approx. 40 g) and this solution was then pumped into the
baffled beaker over a period of 30 minutes while the pH of the
slurry was maintained at 4 by addition of 2.5N NaOH. Upon
complete addition of the FeC1306H20 solution, the pH was raised
to 4.5 and the slurry was allowed to mix for 10 minutes. The
slurry was then heated to 60 C over a period of 30 minutes,
while the pH was maintained at pH 4.5. The pH of the slurry was
then raised to 6.5 over a period of 10 minutes, and allowed to
mix for 10 minutes. Ethylene glycol (approx. 1.384 g) was then
added to the slurry, and allowed to mix at approximately 60 C
for approximately 10 minutes. The slurry was then filtered, and
the wet cake was then re-slurried in degassed deionized water
(90 g) and introduced into the baffled beaker.
[00494] The pH of the solution was then lowered to 5 by
addition of degassed 1M HC1 (0.841g). K2PtC14 (0.459 g) was
dissolved in degassed water (20 mL). The resulting Pt solution
was then added to the baffled beaker over a period of three
minutes. The slurry was then allowed to mix at ambient
conditions (approximately 22 C) for 30 minutes, and then heated
to a temperature of 60 C over a period of 10 minutes.
[00495] The slurry was filtered, and the wet cake was hot
washed twice at 60 C with approximately 100 mL of degassed
water. The resulting sample was then dried in a vacuum oven at
110 C for 12 hours with a small nitrogen stream.
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[00496] The catalyst precursor was then heated at elevated
temperatures up to approximately 755 C in the presence of a
hydrogen/argon stream (4%/96%; v/v) for approximately 120
minutes.
Example 52
[00497] The following preparation was conducted under
nitrogen protection.
[00498] Activated carbon (approximately 10.456 g) and
degassed water (approximately 90 g) were placed in a baffled
beaker and allowed to mix for 20 minutes. FeC1306H20 (2.411 g)
was dissolved in degassed water (approximately 41 g) and this
solution was then pumped into the baffled beaker over a period
of 30 minutes while the pH of the slurry was maintained at 4 by
addition of 2.5N NaOH. Upon complete addition of the FeC1306H20
solution, the pH was raised to 4.5, and allowed to mix for 10
minutes. The slurry was then heated to 60 C over a period of 25
minutes while the pH was maintained at pH 4.5. The pH of the
slurry was then raised to 11 over a period of 30 minutes, and
then allowed to mix for 10 minutes.
[00499] Ethylene glycol (1.382 g) was then added to the
slurry, and allowed to mix at approximately 60 C for
approximately ten minutes. The slurry was then filtered, and
the wet cake was then re-slurried in degassed deionized water
(90 g) and introduced into the baffled beaker.
[00500] The pH of the solution was then lowered to 5 by
addition of degassed 1M degassed HC1 (3.7 g). K2PtC14 (0.552 g)
was dissolved in degassed water (20 g) and the Pt solution was
then introduced into the baffled beaker over a period of three
minutes. The slurry was then allowed to mix at ambient
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172
conditions (approximately 22 C) for 30 minutes and then heated
to a temperature of 60 C over a period of 10 minutes.
[00501] The slurry was then filtered, and the wet cake was
hot washed twice at 60 C with approximately 100 mL of degassed
water. The sample was then dried in a vacuum oven at 110 C for
12 hours with a small nitrogen stream.
[00502] The catalyst precursor was then heated at elevated
temperatures up to approximately 650 C in the presence of a
hydrogen/argon stream (4%/96%; v/v) for approximately 120
minutes.
MTC 6991.4
39-21(53610)A/WO
173
0
Table 24A
t-.)
=
=
Cycle 1 2 3 4 5 6
7 8 9
1-,
w
un
Total CO2 (cc) 1944.2 1977.4 2048.3 2044.4 2055.9
2058.7 2054.7 2065.8 2037.7 1(
un
=
End point (mm) 33.58 34.92 34.08 35.58 35.50
35.58 35.42 35.25 35.83 :
Maximum CO2
Concentration
44.5 41.3 41.8 39.8 39.5 40.0 40.2 41.0
40.6 37.8
(%)
PMIDA (wt.%) ND 0.005 0.005
0.007 0.007 0.106
Glyphosate(wt.%) 5.121 5.341 5.410
5.378 5.433 5.538 n
0
IDA(wt.%) 0.155 0.057 0.048
0.042 0.041 0.039 1.)
-.3
"
CH20 (PPm) 2625 2077 1897
1897 1659 2602 LT'
a,
w
a,
HCOOH(ppm) 5320 5891 5858
5800 5817 6283 1.)
0
H
Pt(ppm) 0.019 0.018 0.018
0.018 0.018 0.022 0
I
H
Fe(ppm) 30.170 2.713 0.577
0.372 0.331 0.541 0
1
1.)
-.3
Iv
n
,-i
cp
w
=
=
'a
.6.
w
u4
c,
w
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174
Example 53
[00503] The following preparation was conducted under
nitrogen protection.
[00504] Activated carbon (10.456 g) and degassed water
(approximately 90 g) were placed in a baffled beaker and allowed
to mix for 20 minutes. FeC1306H20 (2.009 g) was dissolved in
degassed water (approximately 41 g) and the resulting solution
was pumped into the baffled beaker over a period of 30 minutes
while the pH of the slurry was maintained at 4 by addition of
2.5N NaOH. After addition of the FeC1306H20 solution, the pH was
raised to 4.5, and allowed to mix for 10 minutes. The slurry
was then heated to approximately 50 C over a period of 32
minutes, while the pH was maintained at pH 4.5. The pH of the
slurry was then raised to 8 over a period of 15 minutes, and
then allowed to mix for 10 minutes. Ethylene glycol (1.386 g)
was then added to the slurry, and allowed to mix at 60 C for ten
minutes. The slurry was then filtered, and the wet cake was
then re-slurried in degassed deionized water (90 g) and
introduced into the baffled beaker.
[00505] The pH of the solution was then lowered to 5 by
addition of degassed 0.5M HC1 (2.17 g). K2PtC14 (0.460 g) was
dissolved in degassed water (20 g) and the Pt solution was then
introduced into the baffled beaker over a period of three
minutes. The slurry was then allowed to mix at room temperature
for 30 minutes, and then heated to a temperature of 60 C over a
period of 10 minutes. The slurry was then filtered, and the wet
cake hot washed twice at 60 C with approximately 100mL of
degassed water. The sample was then dried in a vacuum oven at
110 C for 12 hours with a small nitrogen stream.
[00506] The catalyst precursor was then heated at elevated
temperatures up to approximately 550 C in the presence of a
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175
hydrogen/argon stream (4%/96%; v/v) for approximately 120
minutes.
Example 54
[00507] This example details preparation of a catalyst
having a nominal Pt content of 2 wt.% and a nominal iron content
of 4 wt.% on an activated carbon support having a Langmuir
surface area of approximately 1500 m2/g. The following
preparation was conducted under nitrogen protection.
[00508] Activated carbon (approximately 10.458 g) and
degassed water (approximately 90 g) were mixed in a baffled
beaker under a nitrogen atmosphere.
[00509] FeC1306H20 (approximately 2.028 g) was dissolved in
degassed water (20 g) and this solution was pumped into the
baffled beaker over a period of approximately 25 minutes. The
pH of the slurry within the baffled beaker was maintained at 4
by introduction of 2.5N degassed NaOH, as necessary. After
addition of the FeC1306H20 solution to the beaker was completed,
the pH of the slurry was raised to approximately 4.5 by addition
of NaOH and the slurry was allowed to mix at ambient conditions
(approximately 22 C) for approximately 10 minutes.
[00510] The slurry was then heated to a temperature of
approximately 60 C over a period of approximately 40 minutes.
During the heating, the pH was maintained at 4.5 with addition
of 2.5N degassed NaOH.
[00511] The pH of the slurry was then raised to
approximately 7.5 over a period of approximately 15 minutes at a
temperature of approximately 60 C, via increases in pH at a rate
of approximately 0.5 pH units per 5 minutes. The slurry was
then allowed to mix at pH of approximately 7.5 for approximately
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176
minutes, and then cooled to ambient conditions (approximately
22 C)
[00512] K2PtC14 (approximately 0.460 g) was dissolved in
degassed water (approximately 20 g) and the resulting Pt
solution was then added to the baffled beaker over a period of
approximately 20 minutes. The resulting slurry was allowed to
mix for approximately 30 minutes. The thus mixed slurry was
then cooled to approximately 60 C over a period of 45 minutes,
and then allowed to mix at 60 C for 15 minutes.
[00513] The resulting slurry was then filtered and then
dried in a vacuum oven at approximately 110 C for approximately
12 hours with a small nitrogen stream to form a Pt/Fe catalyst
precursor.
[00514] The catalyst precursor was then heated at elevated
temperatures up to approximately 950 C in the presence of a
hydrogen/argon stream (2%/98%; v/v) for approximately 120
minutes.
[00515] Table 25 sets forth PMIDA reaction testing results,
platinum leaching data, and iron leaching data for the 2%Pt/4%Fe
finished catalyst.
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177
Table 25
Cycle 1 2 3 4 5
Total CO2 (cc) 2169.6 2196.5 2147.3 2122.5 2062.5
End point(min) 36.42 36.08 37.83 38.42 40.00
Maximum CO2
Concentration
(%) 40.5 39.7 37.8 37.5 36.4
PMIDA (wt.%) ND 0.008 0.008
Glyphosate(wt.%) 5.363 5.520 5.461
IDA(wt.%) 0.087 0.030 0.021 0.017
CH20(ppm) 1408 1143 1247
HCOOH(ppm) 5283 5733 5993
Pt(ppm) 0.122 0.153 0.155
Fe(ppm) 33.310 0.941 0.491
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Example 55
[00516] This example provides microscopy results (conducted
in accordance with Protocol B described in Example 68) for the
catalyst precursor prepared as described in Example 54.
[00517] Fig. 116 is a scanning transmission electron
microscopy (STEM) micrograph of a portion of the surface of the
precursor, including points 1 and 2. Figs. 117 and 118 are
results of energy dispersive x-ray (EDX) spectroscopy analysis
for points 1 and 2, respectively. As shown, these portions of
the precursor surface included iron well-dispersed throughout,
but not all iron had platinum deposited thereon.
[00518] Figs. 119 and 120 are STEM photomicrographs of a
portion of the precursor surface indicating spatial distribution
of metal throughout the carbon particle.
[00519] Figs. 121 and 122 are an STEM micrograph and EELS
line scan for a portion of the precursor surface, 1, identified
in the micrograph. Figs. 123 and 124, and 125 and 126 are also
pairs of STEM micrographs and EELS line scan analysis. These
STEM and EELS results indicate the presence of iron throughout
the carbon particle.
Example 56
[00520] This example details preparation of a catalyst
having a nominal Pt content of 2 wt.% and a nominal iron content
of 4 wt.% on an activated carbon support having a Langmuir
surface area of approximately 1500 m2/g. The following
preparation was conducted under nitrogen protection.
[00521] Activated carbon support (approximately 10.457 g)
was introduced into a baffled beaker under a nitrogen
atmosphere. FeC1306H20 (approximately 2.013 g) and sucrose
(approximately 4.550 g) were dissolved in degassed water
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179
(approximately 85 g). 50 wt.% NaOH (approximately 5.225 g) of
was added to and mixed with the FeC1306H20 - sucrose solution.
The FeC1306H20 - sucrose solution was then poured into the
baffled beaker, and allowed to mix. The resulting slurry was
then heated to approximately 60 C over a period of approximately
minutes.
[00522] Ethylene glycol (approximately 1.263 g) was added
to the baffled beaker and allowed to mix with the slurry for
approximately ten minutes at approximately 60 C. The slurry was
then filtered, and the wet cake was then re-slurried in the
baffled beaker in degassed deionized water (approximately 90 g).
The pH of the resulting slurry was then lowered to approximately
7 by addition of degassed 2M HC1.
[00523] K2PtC14 (0.462 g) was dissolved in degassed water
(approximately 20 g) to form a platinum solution that was pumped
into the baffled beaker over a period of approximately 20
minutes. The resulting slurry was then allowed to mix at
ambient conditions (approximately 22 C) for approximately 30
minutes, and then heated to a temperature of approximately 60 C
over a period of approximately 60 minutes. The final slurry was
then filtered and the wet cake was dried in a vacuum oven at
approximately 110 C for approximately 12 hours with a small
nitrogen stream to form a Pt/Fe catalyst precursor.
[00524] The catalyst precursor was then heated at elevated
temperatures up to approximately 900 C in the presence of a
hydrogen/argon stream (2%/98%; v/v) for approximately 120
minutes.
[00525] Table 26 sets forth PMIDA reaction testing results,
platinum leaching data, and iron leaching data for the 2%Pt/4%Fe
catalyst.
MTC 6991.4
39-21 (53610)A/WO
180
Table 26
0
Cycle 1 2 3 4 5 6
7 8 9 t..)
o
o
Total CO2 (cc) 1765.8 1812.5 1881.3 1908.2 1926.6
1877.7 1891.9 1878.2 1871.1 16C
un
End point(min) 44.08 43.50 41.92 42.25 41.58 43.67
43.08 43.83 43.67 4: '-cli
o
Maximum CO2
Concentration
(%) 36.3 34.7 35.4 34.8 35.6 33.9
34.6 33.8 34.3 3J.
PMIDA (wt.%) 0.005 0.009 0.010
0.009 0.011 0.074
Glyphosate(wt.%) 5.326 5.397 5.348
5.448 5.423 5.568 n
IDA(wt.%) 0.081 0.038 0.032
0.028 0.028 0.027 o
1.)
-3
CH20 (PPra) 3191 2588 2311
2559 2620 2915 "
ul
a,
w
HCOOH (ppm) 6079 6290 6124
6123 6018 6223 a,
1.)
Pt(ppm) <0.01 0.014 0.016
0.014 0.015 0.018 o
H
o
1
Fe(ppm) 55.230 3.238 0.694
0.751 0.457 0.454 H
1
1.)
-3
IV
n
,-i
cp
t..,
'a
.6.
t..,
u,
cA
t..,
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181
Example 57
[00526] This Example details the results of microscopy
analysis (conducted in accordance with Protocol B described in
Example 68) for the finished catalyst prepared as described in
Example 56.
[00527] Figs. 127-132 include microscopy results for the
catalyst after use in PMIDA oxidation testing as described in
Example 56.
[00528] Fig. 127 includes four high resolution electron
photomicrographs (HREM) for various portions of the spent
catalyst surface. These indicate formation of graphite and iron
oxide on the outer regions of metal particles. Fig. 128
includes three STEM micrographs, which indicate the presence of
nanoporous platinum regions.
[00529] Fig. 129 is an STEM micrograph showing various
portions of the spent catalyst surface that were analyzed by EDX
analysis. The results of the EDX analysis are shown in Fig.
130, which indicates the presence of a platinum-rich
composition.
[00530] Fig. 131 is also an STEM micrograph and Fig. 132
the results of EDX analysis for the portions of the spent
catalyst surface. These results indicate the presence of
varying metal compositions.
[00531] Figs. 133-137 include microscopy results for the
finished catalyst prepared as described in Example 56, but prior
to reaction testing.
[00532] Fig. 133 is an STEM photomicrograph identifying a
particle to be analyzed by EELS line scan analysis, the results
of which are shown in Fig. 134. As shown in Fig. 134, a partial
shell of iron oxide was detected.
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182
[00533] Fig. 135 is an HREM photomicrograph highlighting Pt
lattice regions. As shown in Fig. 135, the particle identified
included no more than about 4 Pt lattice fringes. It is
currently believed that each lattice fringe corresponds to a
layer of platinum atoms. That is, the particle identified
included a layer of platinum no more than about 4 platinum atoms
thick.
[00534] Figs. 136 and 137 are HREM photomicrographs
identifying two layers of platinum atoms.
[00535] Fig. 138 provides XRD analysis results, which
indicate formation of an Fe0.75Pt0.25 phase.
Example 58
[00536] This example details preparation of a catalyst
precursor having a nominal Pt content of 2 wt.% and a nominal
iron content of 4 wt.% on an activated carbon support having a
Langmuir surface area of approximately 1500 m2/g. The following
preparation was conducted under nitrogen protection.
[00537] Activated carbon support (approximately 10.456 g)
was introduced into a baffled beaker under a nitrogen
atmosphere. FeC1306H20 (approximately 2.011 g) and sucrose
(approximately 4.511 g) were dissolved in degassed water
(approximately 91.1 g). 50 wt.% NaOH (approximately 5.214 g)
was added to and mixed with the FeC1306H20 - sucrose solution.
The FeC1306H20 - sucrose solution was then poured into the
baffled beaker, and allowed to mix with the activated carbon
support. The resulting slurry was then heated to approximately
40 C over a period of approximately 10 minutes.
[00538] Ethylene glycol (approximately 1.309 g) was added
to the baffled beaker and allowed to mix with the slurry for
approximately ten minutes at approximately 40 C. The slurry was
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183
then filtered, and the wet cake was then re-slurried in the
baffled beaker in degassed deionized water (90 g). The pH of
the resulting slurry was then adjusted/lowered to approximately
7 by addition of degassed 2M HC1 (1.52 g).
[00539] K2PtC14 (approximately 0.461 g) was dissolved in
degassed water (20 g) to form a platinum solution that was
introduced into the baffled beaker over a period of 3 minutes.
The resulting slurry was then allowed to mix at approximately
25 C for approximately 30 minutes, and then heated to a
temperature of approximately 60 C over a period of approximately
40 minutes.
[00540] The final slurry was then filtered and the wet cake
was washed twice by contact with degassed water (approximately
100 g) at a temperature of approximately 60 C. The wet cake was
dried in a vacuum oven at approximately 110 C for approximately
12 hours with a small nitrogen stream to form a Pt/Fe catalyst
precursor.
Example 59
[00541] This example details preparation of a catalyst
having a nominal Pt content of 2 wt.% and a nominal iron content
of 4 wt.% on an activated carbon support having a Langmuir
surface area of approximately 1500 m2/g. The following
preparation was conducted under nitrogen protection.
[00542] Activated carbon support (approximately 10.456 g)
was introduced into a baffled beaker under a nitrogen
atmosphere. FeC1306H20 (approximately 2.011 g) and sucrose
(approximately 4.513 g) were dissolved in degassed water
(approximately 91 g). 50 wt.% NaOH (approximately 5.25 g) was
added to and mixed with the FeC1306H20 - sucrose solution. The
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184
FeC1306H20 - sucrose solution was then poured into the baffled
beaker, and allowed to mix with the activated carbon support.
[00543] Ethylene glycol (approximately 1.31 g) was added to
the baffled beaker and the resulting slurry was heated to a
temperature of approximately 30 C over a period of approximately
15 minutes. The slurry was then filtered, and the wet cake was
then re-slurried in the baffled beaker in cold degassed
deionized water (90 g) at a temperature of approximately 12 C.
The pH of the resulting solution was then lowered to
approximately 7 by addition of degassed 2M HC1 (approximately
0.645 g) and 1M HC1 (approximately 0.461g).
[00544] K2PtC14 (approximately 0.461g) was dissolved in cold
degassed water (approximately 20 g) at a temperature of
approximately 12 C. The platinum solution was then pumped into
the baffled beaker over a period of approximately 20 minutes.
[00545] The final slurry was then filtered and the wet cake
was dried in a vacuum oven at approximately 110 C for
approximately 12 hours with a small nitrogen stream to form a
Pt/Fe catalyst precursor.
[00546] The catalyst precursor was then heated at elevated
temperatures up to approximately 755 C in the presence of a
hydrogen/argon stream (4%/96%; v/v) for approximately 120
minutes.
[00547] Table 27 sets forth PMIDA reaction testing results,
platinum leaching data, and iron leaching data for the 2%Pt/4%Fe
finished catalyst.
MTC 6991.4
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185
0
Table 27
w
o
o
Cycle 1 2 3 4 5 6
7 8 9 10
un
Total CO2 (cc) 1776.6 1830.6 1877.3 1898.8 1846.8
1868.2 1853.1 1825.1 1827.8 1600.2
o
End point(min) 44.75 44.92 43.67 44.00 46.25 45.75
46.25 47.42 47.00 48.50
Maximum CO2
Concentration
(%) 35.6 33.5 33.7 33.7 32.5 32.8
32.6 32.0 32.7 31.7
PMIDA (wt.%) ND 0.003 0.005
0.004 0.006 0.057 n
Glyphosate(wt.%) 5.278 5.463 5.489
5.450 5.508 5.516 o
1.)
-.3
IDA(wt.%) 0.079 0.036 0.031
0.029 0.029 0.029 "
in
a,
w
CH2O(PPm) 3702 2914 2366
2434 2422 2756 a,
1.)
o
HCOOH(ppm) 5549 6036 5987
5882 5850 5842 H
0
I
Pt(ppm) 0.016 0.016 0.018 0.019
0.017 0.017 0.022 H
0
I
KJ
Fe(ppm) 36.130 11.570 2.818 0.552
0.456 0.423 0.375
IV
n
,-i
cp
t..,
'a
.6.
t..,
u,
cA
t..,
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186
Example 60
[00548] Figs. 139-148 include microscopy results (conducted
in accordance with Protocol B described in Example 68) for the
finished catalyst prepared as described in Example 59.
[00549] Fig. 139 is an STEM micrograph identifying the
particle analyzed by EELS line scan analysis, the results of
which are shown in Fig. 140. As shown in Fig. 139, the Fe:Pt
atomic ratio of the particle analyzed was 85.99/14.01. The line
scan results of Fig. 140 indicate formation of an iron oxide
outer layer.
[00550] Fig. 141 is an STEM micrograph indicating the
particle that was analyzed by EDX line scan analysis, the
results of which are shown in Fig. 142. The line scan results
indicate a relatively constant platinum signal, suggesting a
very thin platinum shell, i.e., varying by no more than about
25% during the scan across the particle (e.g., from about 17.5
nm to about 46 nm along the scanning line. As also shown in
Fig. 142, the variation in the magnitude of the iron signal
during the scan across the particle is proportionally greater
than the variation in the platinum signal during the scan across
the particle (i.e., on the order of at least about 1.5:1).
[00551] Fig. 143 is an STEM micrograph and Figs. 144 and
145 the corresponding EELS line scan analysis and EDX line scan
analysis, respectively. The EELS line scan results indicate the
presence of an iron oxide layer. The EDX line scan results
indicate the presence of a thin platinum shell.
[00552] Fig. 146 is an STEM micrograph and Fig. 147 the
corresponding EDX line scan analysis. The line scan results
indicate a relatively constant platinum signal, i.e., ranging by
no more than about 25% during the scan across the particle from
about 9 nm to about 35 nm along the scanning line and a greater
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187
variation in the magnitude of the iron signal as compared to the
variation in the platinum signal (i.e., on the order of about
1.5:1).
[00553] Fig. 148 provides XRD results of analysis conducted
as described in Example 69. These results indicate formation of
an Fe0.75Fe0.25 phase.
[00554] Figs. 149-153 are microscopy results for the spent
catalyst (i.e., after testing in PMIDA oxidation).
[00555] Fig. 149 is an STEM micrograph showing various
porous metal particles at the spent catalyst surface.
[00556] Fig. 150 is an STEM micrograph and Fig. 151 the
corresponding EDX line scan analysis results. Fig. 152 is an
STEM micrograph and Fig. 153 the corresponding EDX line scan
analysis results. These results indicate a platinum-rich
composition throughout the particles analyzed due to leaching of
iron from the core, i.e., inner regions of the particles to form
porous platinum-rich particles.
Example 61
[00557] This example details preparation of a catalyst
precursor having a nominal Pt content of 2 wt.% and a nominal
iron content of 3.5 wt.% on an activated carbon support having a
Langmuir surface area of approximately 1500 m2/g. The following
preparation was conducted under nitrogen protection.
[00558] Activated carbon support (approximately 10.457 g)
was introduced into a baffled beaker under a nitrogen
atmosphere. FeC1306H20 (approximately 1.753 g) and sucrose
(approximately 4.455 g) were dissolved in degassed water
(approximately 90 g). 50 wt.% NaOH (approximately 4.613 g) was
added to and mixed with the FeC1306H20 - sucrose solution. The
FeC1306H20 - sucrose solution was then poured into the baffled
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188
beaker, and allowed to mix with the activated carbon support.
The slurry was then heated a temperature of approximately 60 C
over a period of 10 minutes.
[00559] Ethylene glycol (approximately 1.200 g) was added
to the baffled beaker and allowed to mix with the slurry for
approximately ten minutes at approximately 60 C. The slurry was
then filtered, and the wet cake was then re-slurried in degassed
deionized water (90 g) and introduced into the baffled beaker.
The pH of the resulting slurry was then lowered to approximately
6 by addition of degassed 1M HC1 (3.6 g).
[00560] K2PtC14 (approximately 0.452 g) was dissolved in
degassed water (approximately 20 g) to form a platinum solution
that was introduced into the baffled beaker over a period of
approximately 3 minutes. The resulting slurry was then allowed
to mix at ambient conditions (approximately 22 C) for
approximately 15 minutes, and then heated to a temperature of
approximately 40 C over a period of approximately 12 minutes.
[00561] The final slurry was then filtered and the wet cake
was hot washed twice by contact with degassed water
(approximately 100g) at a temperature of approximately 60 C.
The resulting sample was then dried in a vacuum oven at
approximately 110 C for approximately 12 hours with a small
nitrogen stream.
[00562] The catalyst precursor was then heated at elevated
temperatures up to approximately 755 C in the presence of a
hydrogen/argon stream (4%/96%; v/v) for approximately 120
minutes.
[00563] Fig. 154 provides XRD analysis results for the
finished 2%Pt/3.5%Fe catalyst, which indicate formation of a
Fe3Pt phase.
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[00564] Table 28 sets forth PMIDA reaction testing results,
platinum leaching data, and iron leaching data for the finished
catalyst. Fig. 155 provides XRD analysis results for the
catalyst after reaction testing (i.e., the spent catalyst).
These results indicate formation of a Pt phase.
MTC 6991.4
39-21 (53610)A/WO
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Table 28
0
Cycle 1 2 3 4 5 6
7 8 9 1( r..)
o
o
Total CO2 (cc) 1785.7 1841.8 1913.6 1928.1 1970.6
1956.8 1956.0 1947.8 1967.6 1602.(
1-,
w
un
End point(min) 43.83 41.67 39.83 40.17 40.42 40.75
40.58 41.83 41.67 42.7k
Maximum
un
o
maximum CO2
Concentration
(%) 35.4 36.0 36.9 36.9 36.2 35.7
36.2 35.1 35.4 34.7
PMIDA (wt.%) ND 0.003 0.004
0.004 0.004 0.143
Glyphosate(wt.%) 5.169 5.405 5.405
5.343 5.446 5.430 n
IDA(wt.%) 0.085 0.045 0.039
0.038 0.036 0.036 o
1.)
-.3
CH2O(PPm) 3172 2624 2341
2272 2068 2612 "
LT'
a,
w
HCOOH (ppm) 6258 6539 6489
6391 6313 6465 a,
1.)
Pt(ppm) 0.011 0.013 0.014
0.016 0.016 0.022 0
H
0
I
Fe(ppm) 24.680 2.502 0.584
0.487 0.363 0.362 H
0
I
KJ
-.I
IV
n
,-i
cp
t..,
,.z
'a
.6.
t..,
u,
cA
t..,
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Example 61A
[00565] This example details preparation of a catalyst having
a nominal Pt content of 2 wt.% and a nominal iron content of 4 wt.%
on an activated carbon support having a Langmuir surface area of
approximately 1500 m2/g. The following preparation was conducted
under nitrogen protection.
[00566]Activated carbon (approximately 10.456 g) and degassed
water (approximately 90 g) were mixed in a baffled beaker and
allowed to mix for 20 minutes.
[00567] FeC13=6H20 (approx. 2.009 g) was dissolved in degassed
water (40 g) and this solution was then pumped into the baffled
beaker over a period of 30 minutes while maintaining the pH of the
slurry at 4 with 2.5N NaOH, as necessary. After addition of the
FeC13=6H20 solution to the beaker was completed, the pH of the
slurry was raised to 4.5 and allowed to mix for 10 minutes.
[00568] The slurry was then heated to approximately 60 C over
a period of approximately 30 minutes. During the heating, the pH
was maintained at 4.5. The pH of the slurry was then raised to 11
over a period of 30 minutes, and then allowed to mix for 10
minutes. Ethylene glycol (1.388 g) was then added to the slurry,
and allowed to mix at approximately 60 C for approximately 10
minutes. The slurry was then filtered, and the wet cake was then
re-slurried in the baffled in degassed deionized water (approx. 90
g).
[00569] The pH of the solution was then lowered to 7 by
addition of 0.5M degassed HC1. K2PtC14 (0.460 g) was dissolved in
20 mL of degassed water. The Pt solution was then pumped into the
baffled beaker over a period of 30 minutes. The resulting slurry
was then allowed to mix at ambient conditions (approx. 20 C) for
approximately 30 minutes, and then heated to a temperature of
approximately 60 C over a period of 10 minutes.
[00570] The resulting slurry was then filtered and washed
twice by contact with degassed water (approx. 100 g) at a
temperature of approximately 60 C. The sample was then dried in a
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vacuum oven at approximately 110 C for 12 hours with a small
nitrogen stream to form a Pt/Fe catalyst precursor.
[00571] The catalyst precursor was then heated at elevated
temperatures up to approximately 650 C in the presence of a
hydrogen/argon stream (4%/96%; v/v) for approximately 120 minutes.
V. Platinum-Cobalt
Example 62
[00572] This example details preparation of a catalyst having
a nominal platinum content of approximately 2 wt.% and a nominal
cobalt content of approximately 4 wt.% on an activated carbon
support having a Langmuir surface area of approximately 1500 m2/g.
The following preparation was conducted under nitrogen protection.
[00573] CoC12 (1.686 g) and sucrose (4.499 g) were dissolved
in degassed water (89.4 mL) in a screw top jar that had been
flushed with nitrogen. To this mixture was added 50 wt.% sodium
hydroxide (5.209 g), the jar was flushed with nitrogen, and the
solution was then mixed for one minute.
[00574] Activated carbon support (10.458 g) was added to a 400
mL baffled beaker and the CoC12 solution was then poured into the
baffled beaker, the beaker was flushed with nitrogen, and the
components were allowed to mix at room temperature for
approximately five minutes. The resulting solution was then
heated to approximately 60 C over a period of approximately forty
minutes. Ethylene glycol (approx. 1.272 g) was then added, and
the resulting solution was allowed to mix at approximately 60 C
for approximately twenty minutes.
[00575] The solution was then filtered on a fritted glass
filter, the resulting wet cake was returned to the baffled beaker.
The pH of the solution was reduced to approximately 4.7 by
addition of HC1 (2M).
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[00576] K2PtC14 (approx. 0.460g) was dissolved in degassed
water (20 ml) and the platinum solution was added to the baffled
beaker drop-wise over a period of approximately three minutes.
The resulting solution was allowed to mix at approximately 25 C for
approximately sixty minutes. The solution was then heated to
approximately 60 C over a period of approximately twenty minutes.
The resulting solution was then filtered, and the filtrate was hot
washed twice with in degassed water (120 ml) at approximately
60 C. The sample was then dried in a vacuum oven at 110 C for 12
hours with a nitrogen stream.
[00577] The catalyst precursor was then heated at elevated
temperatures up to approximately 900 C in the presence of a
hydrogen/argon stream (4%/96%; v/v) for approximately 120 minutes.
Example 63
[00578] This example details preparation of a catalyst
precursor having a nominal platinum content of 2 wt.% and a cobalt
content of 4 wt.% on an activated carbon support having a Langmuir
surface area of approximately 1500 m2/g. The following preparation
was conducted under nitrogen protection.
[00579] Activated carbon (10.458 g) was placed in a baffled
beaker. CoC1206H20 (1.685 g) and sucrose (4.566 g) were mixed with
degassed water (89.2 ml) and allowed to dissolve. 5.154 g of 50
wt.% sodium hydroxide was added to the cobalt solution and allowed
to mix. The resulting CoC1206H20 solution was then poured into the
baffled beaker with carbon, and allowed to mix.
[00580] The resulting slurry was then heated to approximately
60 C over a period of twenty minutes. Sodium borohydride (approx.
0.558 g) was dissolved in degassed water (20 ml) to which 2.5N
degassed NaOH (0.329 g) was then added. The sodium borohydride
solution was added to the baffled beaker at approximately 60 C
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over a period of approximately twenty minutes, and then allowed to
mix for ten additional minutes. The slurry was then filtered, and
the wet cake was washed twice at approximately 60 C. The
resulting wet cake was then re-slurried in degassed deionized
water (90 g).
[00581] The pH of the solution was reduced to approximately 5
by addition of degassed 2M HC1. K2PtC14 (0.459 g) was dissolved in
degassed water (20 ml). The Pt solution was then added to the
baffled beaker over a period of approximately three minutes. The
slurry was then allowed to mix at approximately 25 C for
approximately 40 minutes, and then heated to a temperature of
approximately 40 C.
[00582] The resulting slurry was then filtered, and the wet
cake was washed twice with hot water (approx. 100 ml) at approx.
60 C. The resulting sample was then dried in a vacuum oven at
approximately 110 C for 12 hours with a small nitrogen stream.
VI. Platinum-Tin
Example 64
[00583] The following preparation was conducted under nitrogen
protection. Activated carbon (10.457 g) was placed in a baffled
beaker and mixed with degassed water (100 ml).
[00584] SnC1405H20 (2.545 g) and K2PtC14 (0.463 g) were
dissolved in degassed water (20 ml). The Sn/Pt solution was then
pumped into the baffled beaker over a period of approximately
twenty-three minutes. The temperature and pH of the Sn/Pt
solution were raised simultaneously to approximately 60 C and
approximately 7, respectively, over a period of approximately
forty five minutes. The solution was allowed to mix for
approximately thirty minutes.
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[00585] NaBH4 (1.310 g) was dissolved in degassed water (10
ml) and this solution was added to the baffled beaker over a
twenty minute period. The resulting slurry was then allowed to
mix for approximately twenty minutes, the slurry filtered, and the
wet cake was hot washed twice with approximately 100 ml of
degassed water at approximately 60 C. The resulting sample was
then dried in a vacuum oven at 110 C for 12 hours with a small
nitrogen stream.
[00586] The catalyst precursor was then heated at elevated
temperatures up to approximately 545 C in the presence of a
hydrogen/argon stream (2%/98%; v/v) for approximately 120 minutes.
VII. Platinum-Copper
Example 65
[00587] The following preparation was conducted under nitrogen
protection.
[00588] Preparation of nominal 2%Pt4%Cu on activated carbon:
The following was added to a baffled beaker including approx. 10g
of activated carbon: 1.64 g of CuS0405H20 solution, 4.51 g of
sucrose, 90 g of degassed deionized water, and 4.63 g of 50 wt.%
NaOH. The mixture was heated to approx. 40 C and stirred for
approx. 10 minutes with a mechanical agitator. To this slurry was
added 1.71 g of 37% formaldehyde diluted to 17.1 g with degassed
deionized water. The resulting slurry was heated to approx. 40 C
along with continued stirring for approx. 30 minutes (or until
solution became colorless). Then the slurry was filtered, washed
once in the filter, and then re-slurried in water to pH 2.02 by
adding 1M degassed HC1. A solution of 0.454g of K2PtC14 in 10g of
degassed water was then added to the slurry, along with continued
stirring for approx. 30 minutes at ambient conditions. Then the
slurry was heated to approx. 60 C and stirred for approx. 30 more
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minutes. This slurry was then filtered and washed with water, and
dried under vacuum at approx. 110 C under a small stream of
nitrogen. A total of 11.720 g of dried material was recovered.
During heat treatment to a maximum temperature of approximately
950 C in the presence of an argon/hydrogen atmosphere (2%/98%)
(v/v) for approximately 120 minutes, the sample lost 13.5% weight.
[00589] Figs. 155A and 155B include microscopy results for the
finished catalyst. Figs 155C - 155F include microscopy results for
the catalyst after testing in PMIDA oxidation.
Example 66
[00590] This example details preparation of a catalyst having
a nominal Pt content of 2 wt.% and a nominal copper content of
3.75 wt.% on an activated carbon support having a Langmuir surface
area of approximately 1500 m2/g. The following preparation was
conducted under nitrogen protection.
[00591] Activated carbon support (approximately 10.457 g) was
introduced into a baffled beaker under a nitrogen atmosphere.
CuSO4=5H20 (approximately 1.540 g) and sucrose (approximately 4.225
g) were dissolved in degassed water (approximately 91 g). 50 wt.%
NaOH (approximately 4.370 g) was added to and mixed with the
CuSO4=5H20 - sucrose solution, and the resulting solution was then
poured into the baffled beaker, and allowed to mix with the
activated carbon support at a temperature of approximately 29 C for
approximately 20 minutes.
[00592] Formaldehyde (37%) (approximately 1.604 g) was added
to the baffled beaker and allowed to mix with the slurry for
approximately eighty four minutes at approximately 29 C. The
slurry was then filtered, and the wet cake was then re-slurried in
degassed deionized water (90 g) and introduced into the beaker.
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The pH of the resulting slurry was then lowered to approximately 4
by addition of degassed 1M HC1.
[00593] K2PtC14 (approximately 0.427 g) was dissolved in
degassed water (approximately 20 g) to form a platinum solution
that was introduced into the baffled beaker over a period of
approximately 3 minutes. The resulting slurry was then allowed to
mix at ambient conditions (approximately 22 C) for approximately 30
minutes, and then heated to a temperature of approximately 60 C,
and then mixed for approximately an additional 30 minutes.
[00594] The final slurry was then filtered and the wet cake
was hot washed twice at 60 C by contact with degassed water
(approximately 100g). The resulting sample was dried in a vacuum
oven at approximately 110 C for approximately 12 hours with a
small nitrogen stream.
[00595] The catalyst precursor was then heated at elevated
temperatures up to approximately 950 C in the presence of a
hydrogen/argon stream (2%/98%; v/v) for approximately 120 minutes.
[00596] Table 29 sets forth PMIDA reaction testing results,
platinum leaching data, and iron leaching data for the finished
catalyst.
MTC 6991.4
39-21(53610)A/WO
198
Table 29
0
Cycle 1 2 3 4 5 6
7 8 9 r..)
o
o
Total CO2 (cc) 1916.9 2049.0 2048.7 2037.5 2010.9
1996.5 1995.9 1918.9 1920.4 1601
1-,
w
vi
End point(min) 49.00 43.50 42.00 42.17 42.33 42.33
41.58 44.42 44.92 45.
vi
o
Maximum CO2
Concentration
(%) 29.8 32.6 33.7 33.9 34.6 34.9
36.9 33.9 33.8 33.
PMIDA (wt.%) 0.007 0.004 0.006
0.005 0.005 0.217
Glyphosate(wt.%) 5.476 5.553 5.492
5.511 5.474 5.443 n
IDA(wt.%) 0.051 0.021 0.018
0.019 0.019 0.018 0
I.)
-.3
cH2o (ppm) 2208 2057 1905
2105 1876 2517 "
in
a,
w
HCOOH(ppm) 4743 4945 5234
5567 5780 5802 a,
I.)
Pt(ppm) 0.023 0.031 0.033
0.039 0.046 0.068 0
H
0
1
Fe(ppm) 16.930 0.953 0.553
0.387 0.284 0.247 H
0
I
N
-.I
IV
n
,-i
cp
t..,
,.z
'a
.6.
t..,
u,
cA
t..,
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VIII. Testing Protocols
Example 67: Protocol A
[00597] The following example details CO chemisorption
analysis used to determine the exposed metal surface areas of
catalysts prepared as described herein. The method described in
this example is referenced in this specification and appended
claims as "Protocol A."
[00598] This protocol subjects a single sample to two
sequential CO chemisorption cycles.
[00599] Cycle 1 measures initial exposed noble metal at zero
valence state. The sample is vacuum degassed and treated with
oxygen. Next, residual, un-adsorbed oxygen is removed and the
catalyst is then exposed to CO. The volume of CO taken up
irreversibly is used to calculate initial noble metal (e.g., Pt )
site density.
[00600] Cycle 2 measures total exposed noble metal. Without
disturbing the sample after cycle 1, it is again vacuum degassed
and then treated with flowing hydrogen, and again degassed. Next
the sample is treated with oxygen. Finally, residual, non-adsorbed
oxygen is removed and the catalyst is then again exposed to CO.
The volume of CO taken up irreversibly is used to calculate total
exposed noble metal (e.g., Pt ) site density. See, for example,
Webb et al., Analytical Methods in Fine Particle Technology,
Micromeritics Instrument Corp., 1997, for a description of
chemisoprtion analysis. Sample preparation, including degassing,
is described, for example, at pages 129-130.
CA 02725434 2010-10-27
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Equipment:
[00601] Micromeritics (Norcross, GA) ASAP 2010- static
chemisorption instrument; Required gases: UHP hydrogen; carbon
monoxide; UHP helium; oxygen (99.998%); Quartz flow through sample
tube with filler rod; two stoppers; two quartz wool plugs;
Analytical balance.
Preparation:
[00602] Insert quartz wool plug loosely into bottom of sample
tube. Obtain tare weight of sample tube with 1st wool plug. Pre-
weigh approximately 0.25 grams of sample then add this on top of
the 1st quartz wool plug. Precisely measure initial sample weight.
Insert 2nd quartz wool plug above sample and gently press down to
contact sample mass, then add filler rod and insert two stoppers.
Measure total weight (before degas): Transfer sample tube to degas
port of instrument then vacuum to <10 gm Hg while heating under
vacuum to 150 C for approximately 8-12 hours. Release vacuum.
Cool to ambient temperature and reweigh. Calculate weight loss and
final degassed weight (use this weight in calculations).
Cycle 1:
[00603] Secure sample tube on analysis port of static
chemisorption instrument. Flow helium (approximately 85
cm3/minute) at ambient temperature and atmospheric pressure through
sample tube, then heat to 150 C at 5 C/minute. Hold at 150 C for
30 minutes. Cool to 30 C.
[00604] Evacuate sample tube to <10 gm Hg at 30 C. Hold at
30 C for 15 minutes. Close sample tube to vacuum pump and run leak
test. Evacuate sample tube while heating to 70 C at 5 C/min. Hold
for 20 minutes at 70 C.
[00605] Flow oxygen (approximately 75 cm3/minute) through
sample tube at 70 C and atmospheric pressure for 50 minutes.
[00606] Evacuate sample tube at 70 C for 5 minutes.
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[00607] Flow helium (approximately 85 cm3/minute) through
sample tube at atmospheric pressure and increase to 80 C at
C/minute. Hold at 80 C for 15 minutes.
[00608] Evacuate sample tube at 80 C for 60 minutes and hold
under vacuum at 80 C for 60 minutes. Cool sample tube to 30 C and
continue evacuation at 30 C for 30 minutes. Close sample tube to
vacuum pump and run leak test.
[00609] Evacuate sample tube at 30 C for 30 minutes and hold
under vacuum at 30 C for 30 minutes.
[00610] For a first CO analysis, CO uptakes are measured under
static chemisorption conditions at 30 C and starting manifold
pressures of 50, 100, 150, 200, 250, 300, 350 and 400 mm Hg (gauge)
to determine the total amount of CO adsorbed (i.e., both
chemisorbed and physisorbed).
[00611] Pressurize manifold to the starting pressure (e.g., 50
mm Hg). Open valve between manifold and sample tube allowing CO to
contact the sample in the sample tube. Allow the pressure in the
sample tube to equilibrate. The reduction in pressure from the
starting manifold pressure to equilibrium pressure in the sample
tube indicates the volume of CO uptake by the sample.
[00612] Close valve between the manifold and sample tube and
pressurize the manifold to the next starting pressure (e.g., 100 mm
Hg). Open valve between manifold and sample tube allowing CO to
contact the sample in the sample tube. Allow the pressure in the
sample tube to equilibrate to determine the volume of CO uptake by
the sample. Perform for each starting manifold pressure.
[00613] Evacuate sample tube at 30 C for 30 minutes.
[00614] For a second CO analysis, CO uptakes are measured
under static chemisorption conditions at 30 C and starting manifold
pressures of 50, 100, 150, 200, 250, 300, 350 and 400 mm Hg (gauge)
as described above for the first CO analysis to determine the total
amount of CO physisorbed.
Cycle 2:
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[00615]After the second CO analysis of Cycle 1, flow helium
(approximately 85 cm3/minute) at 30 C and atmospheric pressure
through sample tube then heat to 150 C at 5 C/minute. Hold at 150 C
for 30 minutes.
[00616] Cool to 30 C. Evacuate sample tube to <10 gm Hg at
30 C for 15 minutes. Hold at 30 C for 15 minutes.
[00617] Close sample tube to vacuum pump and run leak test.
[00618] Evacuate sample tube at 30 C for 20 minutes.
[00619] Flow hydrogen (approximately 150 cm3/minute) through
sample tube at atmospheric pressure while heating to 150 C at
C/min. Hold at 150 C for 15 minutes.
[00620] Evacuate sample tube at 150 C for 60 minutes. Cool
sample tube to 70 C. Hold at 70 C for 15 minutes.
[00621] Flow oxygen (approximately 75 cm3/minute) through
sample tube at atmospheric pressure and 70 C for 50 minutes.
[00622] Evacuate sample tube at 70 C for 5 minutes.
[00623] Flow helium (approximately 85 cm3/minute) through
sample tube at atmospheric pressure and increase temperature to
80 C at 5 C/minute. Hold at 80 C for 15 minutes. Evacuate sample
tube at 80 C for 60 minutes. Hold under vacuum at 80 C for 60
minutes.
[00624] Cool sample tube to 30 C and continue evacuation at
30 C for 30 minutes. Close sample tube to vacuum pump and run leak
test.
[00625] Evacuate sample tube at 30 C for 30 minutes and hold
for 30 minutes.
[00626] For a first CO analysis, CO uptakes are measured under
static chemisorption conditions at 30 C and starting manifold
pressures of 50, 100, 150, 200, 250, 300, 350 and 400 mm Hg (gauge)
to determine the total amount of CO adsorbed (i.e., both
chemisorbed and physisorbed).
[00627] Pressurize manifold to the starting pressure (e.g., 50
mm Hg). Open valve between manifold and sample tube allowing CO to
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contact the sample in the sample tube. Allow the pressure in the
sample tube to equilibrate. The reduction in pressure from the
starting manifold pressure to equilibrium pressure in the sample
tube indicates the volume of CO uptake by the sample.
[00628] Close valve between the manifold and sample tube and
pressurize the manifold to the next starting pressure (e.g., 100 mm
Hg). Open valve between manifold and sample tube allowing CO to
contact the sample in the sample tube. Allow the pressure in the
sample tube to equilibrate to determine the volume of CO uptake by
the sample. Perform for each starting manifold pressure.
[00629] Evacuate sample tube at 30 C for 30 minutes.
[00630] For a second CO analysis, CO uptakes are measured
under static chemisorption conditions at 30 C and starting manifold
pressures of 50, 100, 150, 200, 250, 300, 350 and 400 mm Hg (gauge)
as described above for the first CO analysis to determine the total
amount of CO physisorbed.
Calculations:
[00631] Plot first and second analysis lines in each cycle:
volume CO physically adsorbed and chemisorbed (1st analysis) and
volume CO physically adsorbed (2nd analysis) (cm3/g at SIP) versus
target CO pressures (mm Hg). Plot the difference between First
and Second analysis lines at each target CO pressure. Extrapolate
the difference line to its intercept with the Y-axis. In Cycle 1,
total exposed Pto (mole CO/g) = Y-intercept of difference
line/22.414 X 1000. In Cycle 2, total exposed Pt (mole CO/g) =
Y-intercept of difference line/22.414 X 1000.
Example 68 (Microscopy): Protocol B
[00632] This Example details microscopy analysis of catalyst
samples of the present invention.
High Resolution Electron Micrographs (HREM):
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[00633] HREM for various catalyst samples were generated using
a Jeol 2100 field emission gun (FEG) transmission electron
microscope (TEM) operated at an accelerating voltage of 200 key.
Samples were placed in the holder as-is without carbon
interference (i.e., the samples were not microtomed and embedded
in an organic-containing material such as an epoxy), and under
conditions that identified lattice fringe rings.
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Atomic Layer Measurements:
[00634] Lattice d spacings of catalyst particles identified by
TEM were measured. These measurements were calibrated based on
the known d spacing (3.84 A) of single crystal silicon (110) that
was also analyzed using the Jeol 2100 FEG TEM at the same
magnification and accelerating voltage (200 KeV). The
measurements were recorded and analyzed using DigitalMicrograph
software. The number of atomic layers of platinum for the
particles analyzed was determined based from the number of
repeating lattice fringe rings observed in the HREM micrographs.
Line Scan Analysis:
[00635] Energy dispersive x-ray spectroscopy (EDX) line scan
analysis was conducted using the Jeol 2100 FEG TEM operated in
scanning transmission electron microscopy (STEM) mode. The probe
size was 1 nm.
[00636] Electron energy loss spectroscopy (EELS) line scan
analysis was conducted using the Jeol 2100 FEG TEM operated in
STEM mode with a probe size of 0.5 nm.
Example 69 (X-Ray Diffraction)
[00637] This example details the method utilized for X-Ray
Diffraction (XRD) analysis for the results reported herein.
Powder samples (less than approx. 0.2 g) were compacted using a
pellet press to form sample pellets for analysis. The sample
pellet was placed on a plastic sample holder for analysis in a
Bruker D8 Discover Diffractometer.
[00638] CuKocX radiation (AcuKx = 1.5418 A) was produced in a
sealed Cu tube at 40 kV and 40 mA. Prior to the experiment, a
korundum sample was used to adjust any peak misalignments.
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[00639] The sample holder was placed on the XYZ stage and
analyzed in locked coupled scan mode; the gun and detector angles
were kept at the same value (i.e., el = 02). XRD data were
collected using a LynxEye0 Position Sensitive Detector (PSD) which
is 103 times more sensitive than regular XRD. For each sample, an
XRD spectrum was collected within the 0-90 20 range with a step
size of 0.02 and a total collection time of approx. 3 hours.
Example 70 (Pore Volume and Surface Area Analysis)
[00640] Various metal-impregnated supports and catalysts were
generally analyzed to determine surface area and pore volume data
as reported herein using a Micromeritics 2010 Micropore analyzer
with a one-torr transducer and a Micromeritics 2020 Accelerated
Surface Area and Porosimetry System, also with a one-torr
transducer. These analysis methods are described in, for example,
Analytical Methods in fine Particle Technology, First Edition,
1997, Micromeritics Instrument Corp.; Atlanta, Georgia (USA); and
Principles and Practice of Heterogeneous Catalysis, 1997, VCH
Publishers, Inc; New York, NY (USA).
[00641] The present invention is not limited to the above
embodiments and can be variously modified. The above description
of the preferred embodiments, including the Examples, is intended
only to acquaint others skilled in the art with the invention, its
principles, and its practical application so that others skilled
in the art may adapt and apply the invention in its numerous
forms, as may be best suited to the requirements of a particular
use.
[00642] With reference to the use of the word(s) comprise or
comprises or comprising in this entire specification (including
the claims below), unless the context requires otherwise, those
words are used on the basis and clear understanding that they are
to be interpreted inclusively, rather than exclusively, and
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applicants intend each of those words to be so interpreted in
construing this entire specification.
[00643] When introducing elements of the present invention or
the preferred embodiments(s) thereof, the articles "a", "an",
"the" and "said" are intended to mean that there are one or more
of the elements. The terms "comprising", "including" and "having"
are intended to be inclusive and mean that there may be additional
elements other than the listed elements.
[00644] In view of the above, it will be seen that the several
objects of the invention are achieved and other advantageous
results attained.
