Note: Descriptions are shown in the official language in which they were submitted.
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PROCESSES FOR MAKING
ETHANOL FROM ACETIC ACID
PRIORITY CLAIM
[0001] This application claims the priority of U.S. Application Number
12/588,727, filed
October 26, 2009, entitled "Tunable Catalyst Gas Phase Hydrogenation of
Carboxylic Acids,"
the entirety of which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to processes for hydrogenating
acetic acid to
form ethanol and to novel catalysts for use in such processes, the catalysts
having high
selectivities for ethanol.
BACKGROUND OF THE INVENTION
[0003] There is a long felt need for an economically viable process to convert
acetic acid to
ethanol which may be used in its own right or subsequently converted to
ethylene which is an
important commodity feedstock as it can be converted to vinyl acetate and/or
ethyl acetate or
any of a wide variety of other chemical products. For example, ethylene can
also be converted
to numerous polymer and monomer products. Fluctuating natural gas and crude
oil prices
contribute to fluctuations in the cost of conventionally produced, petroleum
or natural gas-
sourced ethylene, making the need for alternative sources of ethylene all the
greater when oil
prices rise.
[0004] Catalytic processes for reducing alkanoic acids and other carbonyl
group containing
compounds have been widely studied, and a variety of combinations of
catalysts, supports and
operating conditions have been mentioned in the literature. The reduction of
various carboxylic
acids over metal oxides is reviewed by T. Yokoyama et al. in "Fine chemicals
through
heterogeneous catalysis. Carboxylic acids and derivatives." Chapter 8.3.1,
summarizes some of
the developmental efforts for hydrogenation catalysts for various carboxylic
acids. (Yokoyama,
T.; Setoyama, T. "Carboxylic acids and derivatives." in: "Fine chemicals
through
heterogeneous catalysis." 2001, 370-379.)
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[0005] A series of studies by M. A. Vannice et al. concern the conversion of
acetic acid over
a variety of heterogeneous catalysts (Rachmady W.; Vannice, M. A.; J Catal.
(2002) Vol. 207,
pg. 317-330.) The vapor-phase reduction of acetic acid by H2 over both
supported and
unsupported iron was reported in a separate study. (Rachmady, W.; Vannice, M.
A. J. Catal.
(2002) Vol. 208, pg. 158-169.) Further information on catalyst surface species
and organic
intermediates is set forth in Rachmady, W.; Vannice, M. A., J Catal. (2002)
Vol. 208, pg. 170-
179). Vapor-phase acetic acid hydrogenation was studied further over a family
of supported
Pt-Fe catalysts in Rachmady, W.; Vannice, M. A. J. Catal. (2002) Vol. 209, pg.
87-98) and
Rachmady, W.; Vannice, M. A. J. Catal. (2000) Vol. 192, pg. 322-334).
[0006] Various related publications concerning the selective hydrogenation of
unsaturated
aldehydes may be found in (Djerboua, F.; Benachour, D.; Touroude, R. Applied
Catalysis A:
General 2005, 282, 123-133.; Liberkova, K.; Tourounde, R.J. Mol. Catal. 2002,
180,221-230.;
Rodrigues, E. L.; Bueno, J. M. C. Applied Catalysis A: General 2004, 257, 210-
211.;
Ammari, F.; Lamotte, J.; Touroude, R. J. Catal. 2004,221,32-42; Ammari, F.;
Milone, C.;
Touroude, R. J. Catal. 2005,235, 1-9.; Consonni, M.; Jokic, D.; Murzin, D. Y.;
Touroude, R.J.
Catal. 1999, 188, 165-175.; Nitta, Y.; Ueno, K.; Imanaka, T.; Applied Catal.
1989, 56, 9-22. )
[0007] Studies reporting activity and selectivity over cobalt, platinum and
tin-containing
catalysts in the selective hydrogenation of crotonaldehyde to the unsaturated
alcohol are found
in R. Touroude et al. (Djerboua, F.; Benachour, D.; Touroude, R. Applied
Catalysis A: General
2005, 282, 123-133 as well as Liberkova, K.; Tourounde, R.; J Mol. Catal.
2002, 180, 221-
230) as well as K. Lazar et al. (Lazar, K; Rhodes, W. D.; Borbath, I.;
Hegedues, M.;
Margitfalvi, 1. L. Hyperfine Interactions 2002, 1391140, 87-96.)
[0008] M. Santiago et al. (Santiago, M. A. N.; Sanchez-Castillo, M. A.;
Cortright, R. D.;
Dumesic, 1. A. J Catal. 2000, 193, 16-28.) discuss microcalorimetric, infrared
spectroscopic,
and reaction kinetics measurements combined with quantum-chemical
calculations.
[0009] Catalytic activity in for the acetic acid hydrogenation has also been
reported for
heterogeneous systems with rhenium and ruthenium. (Ryashentseva, M A.;
Minachev, K M;
Buiychev, B. M; Ishchenko, V. M Bull. AcadSci. USSR1988, 2436-2439).
[0010] United States Patent No. 5,149,680 to Kitson et al. describes a process
for the catalytic
hydrogenation of carboxylic acids and their anhydrides to alcohols and/or
esters utilizing
platinum group metal alloy catalysts. United States Patent No. 4,777,303 to
Kitson et al.
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describes a process for the productions of alcohols by the hydrogenation of
carboxylic acids.
United States Patent No. 4,804,791 to Kitson et al. describes another process
for the production
of alcohols by the hydrogenation of carboxylic acids. See also USP 5,061,671;
USP 4, 990,655;
USP 4,985,572; and USP 4,826,795.
[0011] Malinowski et al. (Bull. Soc. Chim. Belg. (1985), 94(2), 93-5), discuss
reaction
catalysis of acetic acid on low-valent titanium heterogenized on support
materials such as silica
(Si02) or titania (Ti02).
[0012] Bimetallic ruthenium-tin/silica catalysts have been prepared by
reaction of tetrabutyl
tin with ruthenium dioxide supported on silica. (Loessard et al., Studies in
Surface Science and
Catalysis (1989), Volume Date 1988, 48 (Struct. React. Surf), 591-600.)
[0013] The catalytic reduction of acetic acid has also been studied in, for
instance,
Hindermann et al., (Hindermann et al., J Chem. Res., Synopses (1980), (11),
373), disclosing
catalytic reduction of acetic acid on iron and on alkali-promoted iron.
[0014] Existing processes suffer from a variety of issues impeding commercial
viability
including: (i) catalysts without requisite selectivity to ethanol; (ii)
catalysts which are possibly
prohibitively expensive and/or nonselective for the formation of ethanol and
that produce
undesirable by-products; (iii) operating temperatures and pressures which are
excessive; and/or
(iv) insufficient catalyst life.
SUMMARY OF THE INVENTION
[0015] The present invention relates to processes for hydrogenating acetic
acid to make
ethanol at high selectivities. In a first embodiment, the invention is
directed to a process for
producing ethanol, comprising hydrogenating acetic acid in the presence of a
catalyst
comprising a first metal, a silicaceous support, and at least one support
modifier. The first
metal may be selected from the group consisting of Group IB, IIB, IIIB, IVB,
VB, VIB, VIIB,
or VIII transitional metal, a lanthanide metal, an actinide metal or a metal
from any of Groups
IIIA, IVA, VA, or VIA. More preferably the first metal may be selected from
the group
consisting of copper, iron, cobalt, nickel, ruthenium, rhodium, palladium,
osmium, iridium,
platinum, titanium, zinc, chromium, rhenium, molybdenum, and tungsten. The
first metal may
be present in an amount of from 0.1 to 25 wt.%, based on the total weight of
the catalyst.
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[0016] In another aspect, the catalyst may comprise a second metal (preferably
different from
the first metal), which may be selected from the group consisting of copper,
molybdenum, tin,
chromium, iron, cobalt, vanadium, tungsten, palladium, platinum, lanthanum,
cerium,
manganese, ruthenium, rhenium, gold, and nickel. In this aspect, the first
metal may be present,
for example, in an amount of from 0.1 to 10 wt.% and the second metal may be
present in an
amount of from 0.1 to 10 wt.%, based on the total weight of the catalyst. In
another aspect, the
catalyst may comprise a third metal (preferably different from the first metal
and the second
metal), which may be selected from the group consisting of cobalt, palladium,
ruthenium,
copper, zinc, platinum, tin, and rhenium and/or which may be present in an
amount of 0.05 and
4 wt.%, based on the total weight of the catalyst.
[0017] Preferably, the first metal is platinum and the second metal is tin
having a molar ratio
of platinum to tin being from 0.4:0.6 to 0.6:0.4. In another preferred
combination, the first
metal is palladium and the second metal is rhenium having molar ratio of
rhenium to palladium
being from 0.7:0.3 to 0.85:0.15.
[0018] Ina preferred aspect of the process, at least 10% of the acetic acid is
converted during
hydrogenation. Optionally, the catalysts have a selectivity to ethanol of at
least 80% and/or a
selectivity to methane, ethane, and carbon dioxide of less than 4%. In one
embodiment, the
catalyst has a productivity that decreases less than 6% per 100 hours of
catalyst usage.
[0019] The silicaceous support may optionally be selected from the group
consisting of silica,
silica/alumina, calcium metasilicate, pyrogenic silica, high purity silica,
and mixtures thereof
and may be present in an amount of 25 wt.% to 99 wt.%, based on the total
weight of the
catalyst. Preferably, the silicaceous support has a surface area of from 50
m2/g to 600 m2/g.
[0020] The support modifier, e.g., metasilicate support modifier, may be
selected from the
group consisting of (i) alkaline earth metal oxides, (ii) alkali metal oxides,
(iii) alkaline earth
metal metasilicates, (iv) alkali metal metasilicates, (v) Group IIB metal
oxides, (vi) Group IIB
metal metasilicates, (vii) Group IIIB metal oxides, (viii) Group IIIB metal
metasilicates, and
mixtures thereof. As one option, the support modifier may be selected from the
group
consisting of oxides and metasilicates of sodium, potassium, magnesium,
calcium, scandium,
yttrium, and zinc, preferably being CaSiO3. The support modifier may be
present in an amount
of 0.1 wt.% to 50 wt.%, based on the total weight of the catalyst.
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[0021] In one embodiment, the hydrogenation is performed in a vapor phase at a
temperature
of from 125 C to 350 C, a pressure of 10 KPa to 3000 KPa, and a hydrogen to
acetic acid mole
ratio of greater than 4:1.
[0022] In another embodiment, the invention relates to a crude ethanol product
(optionally
obtained from the hydrogenation of acetic acid, as discussed above), which
comprises (a)
ethanol in an amount from 15 to 70 wt.%, preferably from 20 to 50 wt.% or,
more preferably,
from 25 to 50 wt.%; (b) acetic acid in an amount from 0 to 80 wt.%, preferably
from 20 to 70
wt.% or, more preferably from 44 to 65 wt.%; (c) water in an amount from 5 to
30 wt.%,
preferably from 10 to 30 wt.% or, more preferably, from 10 to 26 wt; and (d)
any other
compounds in an amount less than 10 wt.%, wherein all weight percents are
based on the total
weight of the crude ethanol product. A preferred crude ethanol product
comprises the ethanol
in an amount from 20 to 50 wt.%; the acetic acid in an amount from 28 to 70
wt.%; the water in
an amount from 10 to 30 wt.%; and any other compounds in an amount less than 6
wt.%. An
additional preferred crude ethanol product comprises the ethanol in an amount
from 25 to 50
wt.%; the acetic acid in an amount from 44 to 65 wt.%; the water in an amount
from 10 to 26
wt.%; and any other compounds in an amount less than 4 wt.%.
[0023] In another embodiment, the invention relates to a process for producing
ethanol
comprising hydrogenating acetic acid in the presence of a catalyst comprising:
Pt,,Pd,,,RexSnyCapSi9Or,
wherein: (i) the ratio of v:y is between 3:2 and 2:3, and/or (ii) the ratio of
w:x is between 1:3
and 1:5; and p and q are selected such that p:q is from 1:20 to 1:200 with r
being selected to
satisfy valence requirements and v and w being selected such that:
0.005 < (3.25v + 1.75w) < 0.05.
q
[0024] In yet another embodiment, the invention relates to a process for
producing ethanol
comprising hydrogenating acetic acid in the presence of a catalyst comprising:
PtvPd,,,RexSnyAIZCapSigOr,
wherein: (i) v and y are between 3:2 and 2:3, and/or (ii) w and x are between
1:3 and 1:5; and p
and z and the relative locations of aluminum and calcium atoms present are
controlled such that
Bronsted acid sites present upon the surface thereof are balanced by a support
modifier; andp
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and q are selected such that p: q is from 1:20 to 1:200 with r being selected
to satisfy valence
requirements, and v and w are selected such that:
0.005:!g (3.25v+1.75w) < 0.05.
q
BRIEF DESCRIPTION OF DRAWINGS
[0025] The invention is described in detail below with reference to the
appended drawings,
wherein like numerals designate similar parts.
[0026] FIG. 1A is a graph of the selectivity to ethanol and ethyl acetate
using a SiO2-Pt.Snl_,,,
catalyst;
[0027] FIG. 1 B is a graph of the productivity to ethanol and ethyl acetate of
the catalyst of
FIG. 1A;
[0028] FIG. 1 C is a graph of the conversion of the acetic acid of the
catalyst of FIG. 1 A;
[0029] FIG. 2A is a graph of the selectivity to ethanol and ethyl acetate
using a SiO2-Re.Pdl_.
catalyst;
[0030] FIG. 2B is a graph of the productivity to ethanol and ethyl acetate of
the catalyst of
FIG. 2A;
[0031] FIG. 2C is a graph of the conversion of the acetic acid of the catalyst
of FIG. 2A;
[0032] FIG. 3A is a graph of the productivity of a catalyst to ethanol at 15
hours of testing;
[0033] FIG. 3B is a graph of the selectivity of the catalyst of FIG. 3A to
ethanol;
[0034] FIG. 4A is a graph of the productivity of a catalyst to ethanol over
100 hours of testing
according to another embodiment of the invention;
[0035] FIG. 4B is a graph of the selectivity of the catalyst of FIG. 4A to
ethanol;
[0036] FIG. 5A is a graph of productivity of a catalyst to ethanol over 20
hours of testing
according to another embodiment of the invention;
[0037] FIG. 5B is a graph of the selectivity of the catalyst of FIG. 5A to
ethanol;
[0038] FIG. 6A is a graph of the conversion of the catalysts of Example 18;
[0039] FIG. 6B is a graph of the productivity of the catalysts of Example 18;
[0040] FIG. 6C is a graph of the selectivity at 250 C of the catalysts of
Example 18; and
[0041] FIG. 6D is a graph of the selectivity at 275 C of the catalysts of
Example 18.
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DETAILED DESCRIPTION OF THE INVENTION
[0042] The present invention relates to processes for producing ethanol by
hydrogenating
acetic acid in the presence of a catalyst. The catalyst employed in the
process comprises at
least one metal, a silicaceous support, and at least one support modifier. The
present invention
also relates to the catalysts used in this process and processes for making
the catalysts. The
hydrogenation reaction may be represented as follows:
0
2 H2
+ H2O
0- OH
CH3 OH
[0043] It has surprisingly and unexpectedly been discovered that the catalysts
of the present
invention provide high selectivities to ethoxylates, such as ethanol and ethyl
acetate, and in
particular to ethanol, when employed in the hydrogenation of acetic acid.
Embodiments of the
present invention beneficially may be used in industrial applications to
produce ethanol on an
economically feasible scale.
[0044] The catalyst of the invention comprises a first metal and optionally
one or more of a
second metal, a third metal or additional metals on the support. In this
context, the numerical
terms "first," "second," "third," etc., when used to modify the word "metal,"
are meant to
indicate that the respective metals are different from one another. The total
weight of all
supported metals present in the catalyst preferably is from 0.1 to 25 wt.%,
e.g., from 0.1 to 15
wt.%, or from 0.1 wt.% to 10 wt.%. For purposes of the present specification,
unless otherwise
indicated, weight percent is based on the total weight the catalyst including
metal and support.
The metal(s) in the catalyst may be present in the form of one or more metal
oxides. For
purposes of determining the weight percent of the metal(s) in the catalyst,
the weight of any
oxygen that is bound to the metal is ignored.
[0045] The first metal may be a Group IB, IIB, IIIB, IVB, VB, VIB, VIIB, or
VIII
transitional metal, a lanthanide metal, an actinide metal or a metal from any
of Groups IIIA,
IVA, VA, or VIA. In a preferred embodiment, the first metal is selected the
group consisting
of copper, iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium,
iridium, platinum,
titanium, zinc, chromium, rhenium, molybdenum, and tungsten. Preferably, the
first metal is
selected from the group consisting of platinum, palladium, cobalt, nickel, and
ruthenium. More
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preferably, the first metal is selected from platinum and palladium. When the
first metal
comprises platinum, it is preferred that the catalyst comprises platinum in an
amount less than 5
wt.%, e.g., less than 3 wt.% or less than 1 wt.%, due to the availability of
platinum.
[0046] As indicated above, the catalyst optionally further comprises a second
metal, which
typically would function as a promoter. If present, the second metal
preferably is selected from
the group consisting of copper, molybdenum, tin, chromium, iron, cobalt,
vanadium, tungsten,
palladium, platinum, lanthanum, cerium, manganese, ruthenium, rhenium, gold,
and nickel.
More preferably, the second metal is selected from the group consisting of
copper, tin, cobalt,
rhenium, and nickel. More preferably, the second metal is selected from tin
and rhenium.
[0047] Where the catalyst includes two or more metals, one metal may act as a
promoter
metal and the other metal is the main metal. For instance, with a platinum/tin
catalyst,
platinum may be considered to be the main metal and tin may be considered the
promoter
metal. For convenience, the present specification refers to the first metal as
the primary
catalyst and the second metal (and optional metals) as the promoter(s). This
should not be taken
as an indication of the underlying mechanism of the catalytic activity.
[0048] If the catalyst includes two or more metals, e.g., a first metal and a
second metal, the
first metal optionally is present in the catalyst in an amount from 0.1 to 10
wt.%, e.g. from 0.1
to 5 wt.%, or from 0.1 to 3 wt.%. The second metal preferably is present in an
amount from 0.1
and 20 wt.%, e.g., from 0.1 to 10 wt.%, or from 0.1 to 5 wt.%. For catalysts
comprising two or
more metals, the two or more metals may be alloyed with one another or may
comprise a non-
alloyed metal solution or mixture.
[0049] The preferred metal ratios may vary somewhat depending on the metals
used in the
catalyst. In some embodiments, the mole ratio of the first metal to the second
metal preferably
is from 10:1 to 1:10, e.g., from 4:1 to 1:4, from 2:1 to 1:2, from 1.5:1 to
1:1.5 or from 1.1:1 to
1:1.1. It has now surprisingly and unexpectedly been discovered that for
platinum/tin catalysts,
platinum to tin molar ratios on the order of from 0.4:0.6 to 0.6:0.4 (or about
1:1) are
particularly preferred in order to form ethanol from acetic acid at high
selectivity, conversion
and productivity, as shown in FIGS. 1 A, 1 B and 1 C. Selectivity to ethanol
may be further
improved by incorporating modified supports as described throughout the
present specification.
[0050] Molar ratios other than 1:1 may be preferred for other catalysts. With
rhenium/palladium catalysts, for example, higher ethanol selectivities may be
achieved at
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higher rhenium loadings than palladium loadings. As shown in FIGS. 2A, 2B and
2C,
preferred rhenium to palladium molar ratios for forming ethanol in terms of
selectivity,
conversion and production are on the order of 0.7:0.3 to 0.85:0.15, or about
0.75:0.25 (3:1).
Again, selectivity to ethanol may be further improved by incorporating
modified supports as
described throughout the present specification.
[0051] In embodiments when the catalyst comprises a third metal, the third
metal may be
selected from any of the metals listed above in connection with the first or
second metal, so
long as the third metal is different from the first and second metals. In
preferred aspects, the
third metal is selected from the group consisting of cobalt, palladium,
ruthenium, copper, zinc,
platinum, tin, and rhenium. More preferably, the third metal is selected from
cobalt, palladium,
and ruthenium. When present, the total weight of the third metal preferably is
from 0.05 and 4
wt.%, e.g., from 0.1 to 3 wt.%, or from 0.1 to 2 wt.%.
[0052] In one embodiment, the catalyst comprises a first metal and no
additional metals (no
second metal, etc.). In this embodiment, the first metal preferably is present
in an amount from
0.1 to 10 wt. %. In another embodiment, the catalyst comprises a combination
of two or more
metals on a support. Specific preferred metal compositions for various
catalysts of this
embodiment of the invention are provided below in Table 1. Where the catalyst
comprises a
first metal and a second metal, the first metal preferably is present in an
amount from 0.1 to 5
wt.% and the second metal preferably is present in an amount from 0.1 to 5
wt.%. Where the
catalyst comprises a first metal, a second metal and a third metal, the first
metal preferably is
present in an amount from 0.1 to 5 wt.%, the second metal preferably is
present in an amount
from 0.1 to 5 wt.%, and the third metal preferably is present in an amount
from 0.1 to 2 wt.%.
In one exemplary embodiment, the first metal is platinum and is present in an
amount from 0.1
to 5 wt.%, the second metal is present in an amount from 0.1 to 5 wt.%, and
the third metal, if
present, preferably is present in an amount from 0.05 to 2 wt.%.
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TABLE 1
EXEMPLARY METAL COMBINATIONS FOR CATALYSTS
First Metal Second Metal Third Metal
Cu Ag
Cu Cr
Cu v
Cu w
Cu Zn
Ni Au
Ni Re
Ni V
Ni W
Pd Co
Pd Cr
Pd Cu
Pd Fe
Pd La
Pd Mo
Pd Ni
Pd Re
Pd Sn
Pd V
Pd W
Pt Co
Pt Cr
Pt Cu
Pt Fe
Pt Mo
Pt Sn
Pt Sn Co
Pt Sn Re
Pt Sn Ru
Pt Sn Pd
Rh Cu
Rh Ni
Ru Co
Ru Cr
Ru Cu
Ru Fe
Ru La
Ru Mo
Ru Ni
Ru Sn
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[0053] Depending primarily on how the catalyst is manufactured, the metals of
the catalysts
of the present invention may be dispersed throughout the support, coated on
the outer surface of
the support (egg shell) or decorated on the surface of the support.
[0054] In addition to one or more metals, the catalysts of the present
invention further
comprise a modified support, meaning a support that includes a support
material and a support
modifier, which adjusts the acidity of the support material. For example, the
acid sites, e.g.
Bronsted acid sites, on the support material may be adjusted by the support
modifier to favor
selectivity to ethanol during the hydrogenation of acetic acid. The acidity of
the support
material may be adjusted by reducing the number or reducing the availability
of Bronsted acid
sites on the support material. The support material may also be adjusted by
having the support
modifier change the pKa of the support material. Unless the context indicates
otherwise, the
acidity of a surface or the number of acid sites thereupon may be determined
by the technique
described in F. Delannay, Ed., "Characterization of Heterogeneous Catalysts";
Chapter III:
Measurement of Acidity of Surfaces, p. 370-404; Marcel Dekker, Inc., N.Y.
1984, the entirety
of which is incorporated herein by reference. It has now been discovered that
in addition to the
metal precursors and preparation conditions employed, metal-support
interactions may have a
strong impact on selectivity to ethanol. In particular, the use of modified
supports that adjust
the acidity of the support to make the support less acidic or more basic
surprisingly and
unexpectedly has now been demonstrated to favor formation of ethanol over
other
hydrogenation products.
[0055] As will be appreciated by those of ordinary skill in the art, support
materials are
selected such that the catalyst system is suitably active, selective and
robust under the process
conditions employed for the formation of ethanol. Suitable support materials
may include, for
example, stable metal oxide-based supports or ceramic-based supports.
Preferred supports
include silicaceous supports, such as silica, silica/alumina, a Group IIA
silicate such as calcium
metasilicate, pyrogenic silica, high purity silica and mixtures thereof. Other
supports may be
used in some embodiments of the present invention, including without
limitation, iron oxide,
alumina, titania, zirconia, magnesium oxide, carbon, graphite, high surface
area graphitized
carbon, activated carbons, and mixtures thereof.
[0056] In preferred embodiments, the support comprises a basic support
modifier having a
low volatility or that is non-volatile. Low volatility modifiers have a rate
of loss that is low
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enough such that the acidity of the support modifier is not reversed during
the life of the
catalyst. Such basic modifiers, for example, may be selected from the group
consisting of: (i)
alkaline earth oxides, (ii) alkali metal oxides, (iii) alkaline earth metal
metasilicates, (iv) alkali
metal metasilicates, (v) Group IIB metal oxides, (vi) Group IIB metal
metasilicates, (vii) Group
IIIB metal oxides, (viii) Group IIIB metal metasilicates, and mixtures
thereof. In addition to
oxides and metasilicates, other types of modifiers including nitrates,
nitrites, acetates, and
lactates may be used in embodiments of the present invention. Preferably, the
support modifier
is selected from the group consisting of oxides and metasilicates of any of
sodium, potassium,
magnesium, calcium, scandium, yttrium, and zinc, and mixtures of any of the
foregoing.
Preferably, the support modifier is a calcium silicate, more preferably
calcium metasilicate
(CaSiO3). If the support modifier comprises calcium metasilicate, it is
preferred that at least a
portion of the calcium metasilicate is in crystalline form.
[0057] The total weight of the modified support, which includes the support
material and the
support modifier, based on the total weight of the catalyst, preferably is
from 75 wt.% to 99.9
wt.%, e.g., from 78 wt.% to 97 wt.%, or from 80 wt.% to 95 wt.%. The support
modifier
preferably is provided in an amount sufficient to adjust the acidity, e.g., by
reducing the
number or reducing the availability of active Bronsted acid sites, and more
preferably to ensure
that the surface of the support is substantially free of active Bronsted acid
sites. In preferred
embodiments, the support modifier is present in an amount from 0.1 wt.% to 50
wt.%, e.g.,
from 0.2 wt.% to 25 wt.%, from 0.5 wt.% to 15 wt.%, or from 1 wt.% to 8 wt.%,
based on the
total weight of the catalyst. In preferred embodiments, the support material
is present in an
amount from 25 wt.% to 99 wt.%, e.g., from 30 wt.% to 97 wt.% or from 35 wt.%
to 95 wt.%.
[0058] In one embodiment, the support material is a silicaceous support
material selected
from the group consisting of silica, silica/alumina, a Group IIA silicate such
as calcium
metasilicate, pyrogenic silica, high purity silica and mixtures thereof. In
the case where silica
is used as the silicaceous support, it is beneficial to ensure that the amount
of aluminum, which
is a common contaminant for silica, is low, preferably under I wt.%, e.g.,
under 0.5 wt.% or
under 0.3 wt.%, based on the total weight of the modified support. In this
regard, pyrogenic
silica is preferred as it commonly is available in purities exceeding 99.7
wt.%. High purity
silica, as used throughout the application, refers to silica in which acidic
contaminants such as
aluminum are present, if at all, at levels of less than 0.3 wt.%, e.g., less
than 0.2 wt.% or less
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than 0.1 wt.%. When calcium metasilicate is used as a support modifier, it is
not necessary to
be quite as strict about the purity of the silica used as the support material
although aluminum
remains undesirable and will not normally be added intentionally. The aluminum
content of
such silica, for example, may be less than 10 wt.%, e.g., less than 5 wt.% or
less than 3 wt.%.
In cases where the support comprises a support modifier in the range of from 2
wt.% to 10
wt.%, larger amount of acidic impurities, such as aluminum, can be tolerated
so long as they
are substantially counter-balanced by an appropriate amount of a support
modifier.
[0059] The surface area of the silicaceous support material, e.g., silica,
preferably is at least
about 50 m2/g, e.g., at least about 100 m2/g, at least about 150 m2/g, at
least about 200 m2/g or
most preferably at least about 250 m2/g. In terms of ranges, the silicaceous
support material
preferably has a surface area of from 50 to 600 m2/g, e.g., from 100 to 500
m2/g or from 100 to
300 m2/g. High surface area silica, as used throughout the application, refers
to silica having a
surface area of at least about 250 m2/g. For purposes of the present
specification, surface area
refers to BET nitrogen surface area, meaning the surface area as determined by
ASTM D6556-
04, the entirety of which is incorporated herein by reference.
[0060] The silicaceous support material also preferably has an average pore
diameter of from
to 100 nm, e.g., from 5 to 30 nm, from 5 to 25 nm or from about 5 to 10 nm, as
determined by
mercury intrusion porosimetry, and an average pore volume of from 0.5 to 2.0
cm3/g, e.g., from
0.7 to 1.5 cm3/g or from about 0.8 to 1.3 cm3/g, as determined by mercury
intrusion
porosimetry.
[0061] The morphology of the support material, and hence of the resulting
catalyst
composition, may vary widely. In some exemplary embodiments, the morphology of
the
support material and/or of the catalyst composition may be pellets,
extrudates, spheres, spray
dried microspheres, rings, pentarings, trilobes, quadrilobes, multi-lobal
shapes, or flakes
although cylindrical pellets are preferred. Preferably, the silicaceous
support material has a
morphology that allows for a packing density of from 0.1 to 1.0 g/cm3, e.g.,
from 0.2 to 0.9
g/cm3 or from 0.5 to 0.8 g/cm3. In terms of size, the silica support material
preferably has an
average particle size, e.g., meaning the diameter for spherical particles or
equivalent spherical
diameter for non-spherical particles, of from 0.01 to 1.0 cm, e.g., from 0.1
to 0.5 cm or from
0.2 to 0.4 cm. Since the one or more metal(s) that are disposed on or within
the modified
support are generally very small in size, they should not substantially impact
the size of the
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overall catalyst particles. Thus, the above particle sizes generally apply to
both the size of the
modified supports as well as to the final catalyst particles.
[0062] A preferred silica support material is SS61138 High Surface Area (HSA)
Silica
Catalyst Carrier from Saint Gobain NorPro. The Saint-Gobain NorPro SS61138
silica contains
approximately 95 wt.% high surface area silica; a surface area of about 250
m2/g; a median
pore diameter of about 12 nm; an average pore volume of about 1.0 cm3/g as
measured by
mercury intrusion porosimetry and a packing density of about 0.352 g/cm3 (22
lb/ft).
[0063] A preferred silica/alumina support material is KA-160 (Sud Chemie)
silica spheres
having a nominal diameter of about 5 mm, a density of about 0.562 g/ml, in
absorptivity of
about 0.583 g H20/g support, a surface area of about 160 to 175 m2/g, and a
pore volume of
about 0.68 ml/g.
[0064] In embodiments where substantially pure ethanol is to be produced at
high selectivity,
as indicated above, controlling the Bronsted acidity of the support material
by incorporating a
support modifier can be quite beneficial. One possible byproduct of the
hydrogenation of
acetic acid is ethyl acetate. According to the present invention, the support
preferably includes
a support modifier that is effective to suppress production of ethyl acetate,
rendering the
catalyst composition highly selective to ethanol. Thus, the catalyst
composition preferably has a
low selectivity toward conversion of acetic acid to ethyl acetate and highly
undesirable
by-products such as alkanes. The acidity of the support preferably is
controlled such that less
than 4%, preferably less than 2% and most preferably less than about 1% of the
acetic acid is
converted to methane, ethane and carbon dioxide. In addition, the acidity of
the support may
be controlled by using a pyrogenic silica or high purity silica as discussed
above.
[0065] In one embodiment, the modified support comprises a support material
and calcium
metasilicate as support modifier in an amount effective to balance Bronsted
acid sites resulting,
for example, from residual alumina in the silica. Preferably, the calcium
metasilicate is present
in an amount from 1 wt.% to 10 wt.%, based on the total weight of the
catalyst, in order to
ensure that the support is essentially neutral or basic in character.
[0066] As the support modifier, e.g., calcium metasilicate, may tend to have a
lower surface
area than the support material, e.g., silicaceous support material, in one
embodiment the
support material comprises a silicaceous support material that includes at
least about 80 wt.%,
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e.g., at least about 85 wt.% or at least about 90 wt.%, high surface area
silica in order to
counteract this effect of including a support modifier.
[0067] In another aspect, the catalyst composition may be represented by the
formula:
Pt,,Pd,RexSnyCapSigOr,
wherein: (i) the ratio of v:y is between 3:2 and 2:3; and/or (ii) the ratio of
w:x is between 1:3
and 1:5. Thus, in this embodiment, the catalyst may comprise (i) platinum and
tin; (ii)
palladium and rhenium; or (iii) platinum, tin, palladium and rhenium. p and q
preferably are
selected such that p:q is from 1:20 to 1:200 with r being selected to satisfy
valence
requirements and v and w being selected such that:
0.005 < (3.25v+1.75w) < 0.05
q
[0068] In this aspect, the process conditions and values of v, w, x, y, p, q,
and r are preferably
chosen such that at least 70% of the acetic acid, e.g., at least 80% or at
least 90%, that is
converted is converted to a compound selected from the group consisting of
ethanol and ethyl
acetate while less than 4% of the acetic acid is converted to alkanes. More
preferably, the
process conditions and values of v, w, x, y, p, q, and r are preferably chosen
such that at least
70% of the acetic acid, e.g., at least 80% or at least 90%, that is converted
is converted to
ethanol, while less than 4% of the acetic acid is converted to alkanes. In
many embodiments of
the present invention, p is selected, in view of any minor impurities present,
to ensure that the
surface of the support is essentially free of active Bronsted acid sites.
[0069] In another aspect, the composition of the catalyst comprises:
Pt,,PdwRe,,SnyAlzCapSigOr,
wherein: (i) v and y are between 3:2 and 2:3; and/or (ii) w and x are between
1:3 and 1:5. p and
z and the relative locations of aluminum and calcium atoms present preferably
are controlled
such that Bronsted acid sites present upon the surface thereof are balanced by
the support
modifier, e.g., calcium metasilicate; p and q are selected such that p: q is
from 1:20 to 1:200
with r being selected to satisfy valence requirements and v and w are selected
such that:
0.005 < (3.25v + 1.75w) < 0.05
q
[0070] Preferably, in this aspect, the catalyst has a surface area of at least
about 100 m2/g,
e.g., at least about 150 m2/g, at least about 200 m2/g or most preferably at
least about 250 m2/g,
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and z and p > z. In many embodiments of the present invention, p is selected,
in view of any
minor impurities present, to also ensure that the surface of the support is
substantially free of
active Bronsted acid sites which seem to facilitate conversion of ethanol into
ethyl acetate.
Thus, as with the previous embodiment, the process conditions and values of v,
w, x, y, p, q,
and r preferably are chosen such that at least 70% of the acetic acid, e.g.,
at least 80% or at
least 90%, that is converted is converted to ethanol, while less than 4% of
the acetic acid is
converted to alkanes.
[00711 Accordingly, without being bound by theory, modification and
stabilization of oxidic
support materials for the catalysts of the present invention by incorporation
of non-volatile
support modifiers having either the effect of. counteracting acid sites
present upon the support
surface or the effect of thermally stabilizing the surface makes it possible
to achieve desirable
improvements in selectivity to ethanol, prolonged catalyst life, or both. In
general, support
modifiers based on oxides in their most stable valence state will have low
vapor pressures and
thus have low volatility or are rather non-volatile. Accordingly, it is
preferred that the support
modifiers are provided in amounts sufficient to: (i) counteract acidic sites
present on the surface
of the support material; (ii) impart resistance to shape change under
hydrogenation
temperatures; or (iii) both. Without being bound by theory, imparting
resistance to shape
change refers to imparting resistance, for example, to sintering, grain
growth, grain boundary
migration, migration of defects and dislocations, plastic deformation and/or
other temperature
induced changes in microstructure.
[00721 Catalysts of the present invention are particulate catalysts in the
sense that, rather than
being impregnated in a wash coat onto a monolithic carrier similar to
automotive catalysts and
diesel soot trap devices, the catalysts of the invention preferably are formed
into particles,
sometimes also referred to as beads or pellets, having any of a variety of
shapes and the
catalytic metals are provided to the reaction zone by placing a large number
of these shaped
catalysts in the reactor. Commonly encountered shapes include extrudates of
arbitrary cross-
section taking the form of a generalized cylinder in the sense that the
generators defining the
surface of the extrudate are parallel lines. As indicated above, any
convenient particle shape
including pellets, extrudates, spheres, spray dried microspheres, rings,
pentarings, trilobes,
quadrilobes and multi-lobal shapes may be used, although cylindrical pellets
are preferred.
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Typically, the shapes are chosen empirically based upon perceived ability to
contact the vapor
phase with the catalytic agents effectively.
[0073] One advantage of catalysts of the present invention is the stability or
activity of the
catalyst for producing ethanol. Accordingly, it can be appreciated that the
catalysts of the
present invention are fully capable of being used in commercial scale
industrial applications for
hydrogenation of acetic acid, particularly in the production of ethanol. In
particular, it is
possible to achieve such a degree of stability such that catalyst activity
will have rate of
productivity decline that is less than 6% per 100 hours of catalyst usage,
e.g., less than 3% per
100 hours or less than 1.5% per 100 hours. Preferably, the rate of
productivity decline is
determined once the catalyst has achieved steady-state conditions.
[0074] In one embodiment, when the catalyst support comprises high purity
silica, with
calcium metasilicate as a support modifier, the catalyst activity may extend
or stabilize, the
productivity and selectivity of the catalyst for prolonged periods extending
into over one week,
over two weeks, and even months, of commercially viable operation in the
presence of acetic
acid vapor at temperatures of 125 C to 350 C at space velocities of greater
than 2500 hr- 1.
[0075] The catalyst compositions of the invention preferably are formed
through metal
impregnation of the modified support, although other processes such as
chemical vapor
deposition may also be employed. Before the metals are impregnated, it
typically is desired to
form the modified support, for example, through a step of impregnating the
support material
with the support modifier. A precursor to the support modifier, such as an
acetate or a nitrate,
may be used. In one aspect, the support modifier, e.g., CaSiO3, is added to
the support
material, e.g., Si02. For example, an aqueous suspension of the support
modifier may be
formed by adding the solid support modifier to deionized water, followed by
the addition of
colloidal support material thereto. The resulting mixture may be stirred and
added to additional
support material using, for example, incipient wetness techniques in which the
support modifier
is added to a support material having the same pore volume as the volume of
the support
modifier solution. Capillary action then draws the support modifier into the
pores in the support
material. The modified support can then be formed by drying and calcining to
drive off water
and any volatile components within the support modifier solution and
depositing the support
modifier on the support material. Drying may occur, for example, at a
temperature of from
50 C to 300 C, e.g., from 100 C to 200 C or about 120 C, optionally for a
period of from 1 to
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24 hours, e.g., from 3 to 15 hours or from 6 to 12 hours. Once formed, the
modified supports
may be shaped into particles having the desired size distribution, e.g., to
form particles having
an average particle size in the range of from 0.2 to 0.4 cm. The supports may
be extruded,
pelletized, tabletized, pressed, crushed or sieved to the desired size
distribution. Any of the
known methods to shape the support materials into desired size distribution
can be employed.
Calcining of the shaped modified support may occur, for example, at a
temperature of from
250 C to 800 C, e.g., from 300 to 700 C or about 500 C, optionally for a
period of from 1 to 12
hours, e.g., from 2 to 10 hours, from 4 to 8 hours or about 6 hours.
[0076] In a preferred method of preparing the catalyst, the metals are
impregnated onto the
modified support. A precursor of the first metal (first metal precursor)
preferably is used in the
metal impregnation step, such as a water soluble compound or water dispersible
compound/complex that includes the first metal of interest. Depending on the
metal precursor
employed, the use of a solvent, such as a water, glacial acetic acid or an
organic solvent, may
be preferred. The second metal also preferably is impregnated into the
modified support from a
second metal precursor. If desired, a third metal or third metal precursor may
also be
impregnated into the modified support.
[0077] Impregnation occurs by adding, optionally drop wise, either or both the
first metal
precursor and/or the second metal precursor and/or additional metal
precursors, preferably in
suspension or solution, to the dry modified support. The resulting mixture may
then be heated,
e.g., optionally under vacuum, in order to remove the solvent. Additional
drying and calcining
may then be performed, optionally with ramped heating to form the final
catalyst composition.
Upon heating and/or the application of vacuum, the metal(s) of the metal
precursor(s)
preferably decompose into their elemental (or oxide) form. In some cases, the
completion of
removal of the liquid carrier, e.g., water, may not take place until the
catalyst is placed into use
and calcined, e.g., subjected to the high temperatures encountered during
operation. During the
calcination step, or at least during the initial phase of use of the catalyst,
such compounds are
converted into a catalytically active form of the metal or a catalytically
active oxide thereof.
[0078] Impregnation of the first and second metals (and optional additional
metals) into the
modified support may occur simultaneously (co-impregnation) or sequentially.
In
simultaneous impregnation, the first and second metal precursors (and
optionally additional
metal precursors) are mixed together and added to the modified support
together, followed by
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drying and calcination to form the final catalyst composition. With
simultaneous impregnation,
it may be desired to employ a dispersion agent, surfactant, or solubilizing
agent, e.g.,
ammonium oxalate, to facilitate the dispersing or solubilizing of the first
and second metal
precursors in the event the two precursors are incompatible with the desired
solvent, e.g., water.
[0079] In sequential impregnation, the first metal precursor is first added to
the modified
support followed by drying and calcining, and the resulting material is then
impregnated with
the second metal precursor followed by an additional drying and calcining step
to form the final
catalyst composition. Additional metal precursors (e.g., a third metal
precursor) may be added
either with the first and/or second metal precursor or an a separate third
impregnation step,
followed by drying and calcination. Of course, combinations of sequential and
simultaneous
impregnation may be employed if desired.
[0080] Suitable metal precursors include, for example, metal halides, amine
solubilized metal
hydroxides, metal nitrates or metal oxalates. For example, suitable compounds
for platinum
precursors and palladium precursors include chloroplatinic acid, ammonium
chloroplatinate,
amine solubilized platinum hydroxide, platinum nitrate, platinum tetra
ammonium nitrate,
platinum chloride, platinum oxalate, palladium nitrate, palladium tetra
ammonium nitrate,
palladium chloride, palladium oxalate, sodium palladium chloride, and sodium
platinum
chloride. Generally, both from the point of view of economics and
environmental aspects,
aqueous solutions of soluble compounds of platinum are preferred. In one
embodiment, the
first metal precursor is not a metal halide and is substantially free of metal
halides. Without
being bound to theory, such non-(metal halide) precursors are believed to
increase selectivity to
ethanol. A particularly preferred precursor to platinum is platinum ammonium
nitrate,
Pt(NH3)4(NO4)2.
[0081] In one aspect, the "promoter" metal or metal precursor is first added
to the modified
support, followed by the "main" or "primary" metal or metal precursor. Of
course the reverse
order of addition is also possible. Exemplary precursors for promoter metals
include metal
halides, amine solubilized metal hydroxides, metal nitrates or metal oxalates.
As indicated
above, in the sequential embodiment, each impregnation step preferably is
followed by drying
and calcination. In the case of promoted bimetallic catalysts as described
above, a sequential
impregnation may be used, starting with the addition of the promoter metal
followed by a
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second impregnation step involving co-impregnation of the two principal
metals, e.g., Pt and
Sn.
[0082] As an example, PtSn/CaSiO3 on Si02 may be prepared by a first
impregnation of
CaSiO3 onto the Si02, followed by the co-impregnation with Pt(NH3)4(NO4)2 and
Sn(AcO)2.
Again, each impregnation step may be followed by drying and calcination steps.
In most cases,
the impregnation may be carried out using metal nitrate solutions. However,
various other
soluble salts, which upon calcination release metal ions, can also be used.
Examples of other
suitable metal salts for impregnation include, metal acids, such as perrhenic
acid solution, metal
oxalates, and the like. In those cases where substantially pure ethanol is to
be produced, it is
generally preferable to avoid the use of halogenated precursors for the
platinum group metals,
using the nitrogenous amine and/or nitrate based precursors instead.
[0083] The process of hydrogenating acetic acid to form ethanol according to
one
embodiment of the invention may be conducted in a variety of configurations
using a fixed bed
reactor or a fluidized bed reactor as one of skill in the art will readily
appreciate. In many
embodiments of the present invention, an "adiabatic" reactor can be used; that
is, there is little
or no need for internal plumbing through the reaction zone to add or remove
heat.
Alternatively, a shell and tube reactor provided with a heat transfer medium
can be used. In
many cases, the reaction zone may be housed in a single vessel or in a series
of vessels with
heat exchangers therebetween. It is considered significant that acetic acid
reduction processes
using the catalysts of the present invention may be carried out in adiabatic
reactors as this
reactor configuration is typically far less capital intensive than tube and
shell configurations.
[0084] Typically, the catalyst is employed in a fixed bed reactor, e.g., in
the shape of an
elongated pipe or tube where the reactants, typically in the vapor form, are
passed over or
through the catalyst. Other reactors, such as fluid or ebullient bed reactors,
can be employed, if
desired. In some instances, the hydrogenation catalysts may be used in
conjunction with an
inert material to regulate the pressure drop of the reactant stream through
the catalyst bed and
the contact time of the reactant compounds with the catalyst particles.
[0085] The hydrogenation reaction may be carried out in either the liquid
phase or vapor
phase. Preferably the reaction is carried out in the vapor phase under the
following conditions.
The reaction temperature may the range from of 125 C to 350 C, e.g., from 200
C to 325 C,
from 225 C to about 300 C, or from 250 C to about 300 C. The pressure may
range from 10
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KPa to 3000 KPa (about 0.1 to 30 atmospheres), e.g., from 50 KPa to 2300 KPa,
or from 100
KPa to 1500 KPa. The reactants may be fed to the reactor at a gas hourly space
velocities
(GHSV) of greater than 500 hr-1, e.g., greater than 1000 hr-1, greater than
2500 hr-1 and even
greater than 5000 hr-1. In terms of ranges the GHSV may range from 50 hr-' to
50,000 hr-1, e.g.,
from 500 hr-1 to 30,000 hr-1, from 1000 hr-1 to 10,000 hr-1, or from 1000 hr-1
to 6500 hr-1.
[0086] In another aspect of the process of this invention, the hydrogenation
is carried out at a
pressure just sufficient to overcome the pressure drop across the catalytic
bed at the GHSV
selected, although there is no bar to the use of higher pressures, it being
understood that
considerable pressure drop through the reactor bed may be experienced at high
space velocities,
e.g., 5000 hr-1 or 6,500 hr-1.
[0087] Although the reaction consumes two moles of hydrogen per mole of acetic
acid to
produce one mole of ethanol, the actual molar ratio of hydrogen to acetic acid
in the feed
stream may vary from about 100:1 to 1:100, e.g., from 50:1 to 1:50, from 20:1
to 1:2, or from
12:1 to 1:1. Most preferably, the molar ratio of hydrogen to acetic acid is
greater than 4:1, e.g.,
greater than 5:1 or greater than 10:1.
[0088] Contact or residence time can also vary widely, depending upon such
variables as
amount of acetic acid, catalyst, reactor, temperature and pressure. Typical
contact times range
from a fraction of a second to more than several hours when a catalyst system
other than a fixed
bed is used, with preferred contact times, at least for vapor phase reactions,
from 0.1 to 100
seconds, e.g., from 0.3 to 80 seconds or from 0.4 to 30 seconds.
[0089] The acetic acid may be vaporized at the reaction temperature, and then
the vaporized
acetic acid can be fed along with hydrogen in undiluted state or diluted with
a relatively inert
carrier gas, such as nitrogen, argon, helium, carbon dioxide and the like. For
reactions run in
the vapor phase, the temperature should be controlled in the system such that
it does not fall
below the dew point of acetic acid.
[0090] In particular, using catalysts and processes of the present invention
may achieve
favorable conversion of acetic acid and favorable selectivity and productivity
to ethanol. For
purposes of the present invention, the term conversion refers to the amount of
acetic acid in the
feed that is convert to a compound other than acetic acid. Conversion is
expressed as a mole
percentage based on acetic acid in the feed.
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[0091] The conversion of acetic acid (AcOH) is calculated from gas
chromatography (GC)
data using the following equation:
AcOH Conv. (%) =100 * mmol AcOH (feed stream) - mmol AcOH (GC)
mmol AcOH (feed stream)
[0092] For purposes of the present invention, the conversion maybe at least
10%, e.g., at
least 20%, at least 40%, at least 50%, at least 60%, at least 70% or at least
80%. Although
catalysts that have high conversions are desirable, such as at least 80% or at
least 90%, a low
conversion may be acceptable at high selectivity for ethanol. It is, of
course, well understood
that in many cases, it is possible to compensate for conversion by appropriate
recycle streams
or use of larger reactors, but it is more difficult to compensate for poor
selectivity.
[0093] "Selectivity" is expressed as a mole percent based on converted acetic
acid. It should
be understood that each compound converted from acetic acid has an independent
selectivity
and that selectivity is independent from conversion. For example, if 50 mole %
of the
converted acetic acid is converted to ethanol, we refer to the ethanol
selectivity as 50%.
Selectivity to ethanol (EtOH) is calculated from gas chromatography (GC) data
using the
following equation:
EtOH Sel. (%) =100 * mmol EtOH (GC)
Total mmol C (GC) _ mmol AcOH (feed stream)
2
[0094] wherein "Total mmol C (GC)" refers to total mmols of carbon from all of
the products
analyzed by gas chromatograph.
[0095] For purposes of the present invention, the selectivity to ethoxylates
of the catalyst is at
least 60%, e.g., at least 70%, or at least 80%. As used herein, the term
"ethoxylates" refers
specifically to the compounds ethanol, acetaldehyde, and ethyl acetate.
Preferably, the
selectivity to ethanol is at least 80%, e.g., at least 85% or at least 88%. In
embodiments of the
present invention is also desirable to have low selectivity to undesirable
products, such as
methane, ethane, and carbon dioxide. The selectivity to these undesirable
products is less than
4%, e.g., less than 2% or less than 1 %. Preferably, no detectable amounts of
these undesirable
products are formed during hydrogenation. In several embodiments of the
present invention,
formation of alkanes is low, usually under 2%, often under 1%, and in many
cases under 0.5%
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of the acetic acid passed over the catalyst is converted to alkanes, which
have little value other
than as fuel.
[0096] Productivity refers to the grams of a specified product, e.g., ethanol,
formed during the
hydrogenation based on the kilogram of catalyst used per hour. In one
embodiment of the
present invention, a productivity of at least 200 grams of ethanol per
kilogram catalyst per
hour, e.g., at least 400 grams of ethanol or least 600 grams of ethanol, is
preferred. In terms of
ranges, the productivity preferably is from 200 to 3,000 grams of ethanol per
kilogram catalyst
per hour, e.g., from 400 to 2,500 or from 600 to 2,000.
[0097] Some catalysts of the present invention may achieve a conversion of
acetic acid of at
least 10%, a selectivity to ethanol of at least 80%, and a productivity of at
least 200 g of ethanol
per kg of catalyst per hour. A subset of catalysts of the invention may
achieve a conversion of
acetic acid of at least 50%, a selectivity to ethanol of at least 80%, a
selectivity to undesirable
compounds of less than 4%, and a productivity of at least 600 g of ethanol per
kg of catalyst per
hour.
[0098] In another embodiment, the invention is to a crude ethanol product
formed by
processes of the present invention. The crude ethanol product produced by the
hydrogenation
process of the present invention, before any subsequent processing, such as
purification and
separation, typically will comprise primarily unreacted acetic acid and
ethanol. In some
exemplary embodiments, the crude ethanol product comprises ethanol in an
amount from 15
wt.% to 70 wt.%, e.g., from 20 wt.% to 50 wt.%, or from 25 wt.% to 50 wt.%,
based on the
total weight of the crude ethanol product. Preferably, the crude ethanol
product contains at
least 22 wt.% ethanol, at least 28 wt.% ethanol or at least 44 wt.% ethanol.
The crude ethanol
product typically will further comprise unreacted acetic acid, depending on
conversion, for
example, in an amount from 0 to 80 wt%, e.g., from 5 to 80 wt%, from 20 to 70
wt.%, from 28
to 70 wt.% or from 44 to 65 wt.%. Since water is formed in the reaction
process, water will
also be present in the crude ethanol product, for example, in amounts ranging
from 5 to 30
wt.%, e.g., from 10 to 30 wt.% or from 10 to 26 wt.%. Other components, such
as, for
example, esters, ethers, aldehydes, ketones, alkanes, and carbon dioxide, if
detectable,
collectively may be present in amounts less than 10 wt.%, e.g., less than 6 or
less than 4 wt.%.
In terms of ranges other components may be present in an amount from 0.1 to 10
wt.%, e.g.,
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from 0.1 to 6 wt.%, or from 0.1 to 4 wt.%. Thus, exemplary crude ethanol
compositional
ranges in various embodiments of the invention are provided below in Table 2.
TABLE 2
CRUDE ETHANOL PRODUCT COMPOSITIONS
Conc. Conc. Conc. Conc.
Component (wt.%) (wt.%) (wt.%) (wt.%)
Ethanol 15-70 15-70 20-50 25-50
Acetic Acid 5-80 20-70 28-70 44-65
Water 5-30 5-30 10-30 10-26
Other <10 <10 <6 <4
[0099] In a preferred embodiment, the crude ethanol product is formed over a
platinum/tin
catalyst on a modified silica support, e.g., modified with CaSiO3. Depending
on the specific
catalyst and process conditions employed, the crude ethanol product may have
any of the
compositions indicated below in Table 3.
TABLE 3
CRUDE ETHANOL PRODUCT COMPOSITIONS
Comp. A Comp. B Comp. C
Component Conc. (wt.%) Conc. (wt.%) Conc. (wt.%)
Ethanol 17 26 45
Acetic Acid 74 53 20
Water 7 13 25
Other 2 8 10
[0100] The raw materials used in connection with the process of this invention
may be
derived from any suitable source including natural gas, petroleum, coal,
biomass and so forth.
It is well known to produce acetic acid through methanol carbonylation,
acetaldehyde
oxidation, ethylene oxidation, oxidative fermentation, and anaerobic
fermentation. As
petroleum and natural gas prices fluctuate becoming either more or less
expensive, methods for
producing acetic acid and intermediates such as methanol and carbon monoxide
from alternate
carbon sources have drawn increasing interest. In particular, when petroleum
is relatively
expensive compared to natural gas, it may become advantageous to produce
acetic acid from
synthesis gas ("syn gas") that is derived from any available carbon source.
United States Patent
No. 6,232,352 to Vidalin, the disclosure of which is incorporated herein by
reference, for
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WO 2011/053365 PCT/US2010/022947
example, teaches a method of retrofitting a methanol plant for the manufacture
of acetic acid.
By retrofitting a methanol plant, the large capital costs associated with CO
generation for a new
acetic acid plant are significantly reduced or largely eliminated. All or part
of the syn gas is
diverted from the methanol synthesis loop and supplied to a separator unit to
recover CO and
hydrogen, which are then used to produce acetic acid. In addition to acetic
acid, the process
can also be used to make hydrogen which may be utilized in connection with
this invention.
[0101] United States Patent No. RE 35,377 to Steinberg et al., also
incorporated herein by
reference, provides a method for the production of methanol by conversion of
carbonaceous
materials such as oil, coal, natural gas and biomass materials. The process
includes
hydrogasification of solid and/or liquid carbonaceous materials to obtain a
process gas which is
steam pyrolized with additional natural gas to form synthesis gas. The syn gas
is converted to
methanol which may be carbonylated to acetic acid. The method likewise
produces hydrogen
which may be used in connection with this invention as noted above. See also,
United States
Patent No. 5,821,111 to Grady et al., which discloses a process for converting
waste biomass
through gasification into synthesis gas as well as United States Patent No.
6,685,754 to Kindig
et al., the disclosures of which are incorporated herein by reference.
[0102] Alternatively, acetic acid in vapor form may be taken directly as crude
product from
the flash vessel of a methanol carbonylation unit of the class described in
United States Patent
No. 6,657,078 to Scates et al., the entirety of which is incorporated herein
by reference. The
crude vapor product, for example, may be fed directly to the ethanol synthesis
reaction zones of
the present invention without the need for condensing the acetic acid and
light ends or
removing water, saving overall processing costs.
[0103] Ethanol, obtained from hydrogenation processes of the present
invention, may be
used in its own right as a fuel or subsequently converted to ethylene which is
an important
commodity feedstock as it can be converted to polyethylene, vinyl acetate
and/or ethyl acetate
or any of a wide variety of other chemical products. For example, ethylene can
also be
converted to numerous polymer and monomer products. The dehydration of ethanol
to
ethylene is shown below.
OH
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[0104] Any of known dehydration catalysts can be employed in to dehydrate
ethanol, such
as those described in copending applications U.S. Application No. 12/221,137
and U.S.
Application No. 12/221,138, the entire contents and disclosures of which are
hereby
incorporated by reference. A zeolite catalyst, for example, may be employed as
the
dehydration catalyst. While any zeolite having a pore diameter of at least
about 0.6 nm can be
used, preferred zeolites include dehydration catalysts selected from the group
consisting of
mordenites, ZSM-5, a zeolite X and a zeolite Y. Zeolite X is described, for
example, in U.S.
Pat. No. 2,882,244 and zeolite Y in U.S. Pat. No. 3,130,007, the entireties of
which are hereby
incorporated by reference.
[0105] Ethanol may also be used as a fuel, in pharmaceutical products,
cleansers, sanitizers,
hydrogenation transport or consumption. Ethanol may also be used as a source
material for
making ethyl acetate, aldehydes, and higher alcohols, especially butanol. In
addition, any ester,
such as ethyl acetate, formed during the process of making ethanol according
to the present
invention may be further reacted with an acid catalyst to form additional
ethanol as well as
acetic acid, which may be recycled to the hydrogenation process.
[0106] The invention is described in detail below with reference to numerous
embodiments
for purposes of exemplification and illustration only. Modifications to
particular embodiments
within the spirit and scope of the present invention, set forth in the
appended claims, will be
readily apparent to those of skill in the art.
[0107] The following examples describe the procedures used for the preparation
of various
catalysts employed in the process of this invention.
Examples
Catalyst Preparations (general)
[0108] The catalyst supports were dried at 120 C overnight under circulating
air prior to
use. All commercial supports (i.e., Si02, Zr02) were used as a 14/30 mesh, or
in its original
shape (1/16 inch or 1/8 inch pellets) unless mentioned otherwise. Powdered
materials (i.e.,
CaSiO3) were pelletized, crushed and sieved after the metals had been added.
The individual
catalyst preparations are described in detail below.
Example 1 - Si02-CaSiO3(5 -Pt(3)-Sn(1.8) Catalyst
[0109] The catalyst was prepared by first adding CaSiO3 (Aldrich) to the Si02
catalyst
support, followed by the addition of Pt/Sn. First, an aqueous suspension of
CaSi03 (-< 200
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mesh) was prepared by adding 0.52 g of the solid to 13 ml of deionized H2O,
followed by the
addition of 1.0 ml of colloidal Si02 (15 wt.% solution, NALCO). The suspension
was stirred
for 2 hours at room temperature and then added to 10.0 g of Si02 catalyst
support (14/30 mesh)
using incipient wetness technique. After standing for 2 hours, the material
was evaporated to
dryness, followed by drying at 120 C overnight under circulating air and
calcination at 500 C
for 6 hours. All of the Si02-CaSiO3 material was then used for Pt/Sn metal
impregnation.
[01101 The catalysts were prepared by first adding Sn(OAc)2 (tin acetate,
Sn(OAc)2 from
Aldrich) (0.4104 g, 1.73 mmol) to a vial containing 6.75 ml of 1:1 diluted
glacial acetic acid
(Fisher). The mixture was stirred for 15 min at room temperature, and then,
0.6711 g (1.73
mmol) of solid Pt(NH3)4(NO3)2 (Aldrich) were added. The mixture was stirred
for another 15
min at room temperature, and then added drop wise to 5.0 g of Si02-CaSiO3
support, in a 100
ml round-bottomed flask. The metal solution was stirred continuously until all
of the Pt/Sn
mixture had been added to the Si02-CaSiO3 support while rotating the flask
after every addition
of metal solution. After completing the addition of the metal solution, the
flask containing the
impregnated catalyst was left standing at room temperature for two hours. The
flask was then
attached to a rotor evaporator (bath temperature 80 C), and evacuated until
dried while slowly
rotating the flask. The material was then dried further overnight at 120 C,
and then calcined
using the following temperature program: 25-4 160 C/ramp 5.0 deg/min; hold for
2.0 hours;
160-* 500 C/ramp 2.0 deg/min; hold for 4 hours. Yield: 11.21 g of dark grey
material.
Example 2 - KAl60-CaSiO-(8)-Pt(3)-Sn(1.8)
[01111 The material was prepared by first adding CaSiO3 to the KA160 catalyst
support
(Si02-(0.05) A1203, Sud Chemie, 14/30 mesh), followed by the addition of
Pt/Sn. First, an
aqueous suspension of CaSiO3 (5 200 mesh) was prepared by adding 0.42 g of the
solid to 3.85
ml of deionized H2O, followed by the addition of 0.8 ml of colloidal Si02 (15
wt.% solution,
NALCO). The suspension was stirred for 2 hours at room temperature and then
added to 5.0 g
of KA160 catalyst support (14/30 mesh) using incipient wetness technique.
After standing for
2 hours, the material was evaporated to dryness, followed by drying at 120 C
overnight under
circulating air and calcinations at 500 C for 6 hours. All of the KA160-CaSiO3
material was
then used for Pt/Sn metal impregnation.
[01121 The catalysts were prepared by first adding Sn(OAc)2 (tin acetate,
Sn(OAc)2 from
Aldrich) (0.2040 g, 0.86 mmol) to a vial containing 6.75 ml of 1:1 diluted
glacial acetic acid
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(Fisher). The mixture was stirred for 15 min at room temperature, and then,
0.3350 g (0.86
mmol) of solid Pt(NH3)4(NO3)2 (Aldrich) were added. The mixture was stirred
for another 15
min at room temperature, and then added drop wise to 5.0 g of SiO2-CaSiO3
support, in a 100
ml round-bottomed flask. After completing the addition of the metal solution,
the flask
containing the impregnated catalyst was left standing at room temperature for
two hours. The
flask was then attached to a rotor evaporator (bath temperature 80 C), and
evacuated until dried
while slowly rotating the flask. The material was then dried further overnight
at 120 C, and
then calcined using the following temperature program: 25-*160 C/ramp 5.0
deg/min; hold for
2.0 hours; 160->500 C/ramp 2.0 deg/min; hold for 4 hours. Yield: 5.19 g of tan-
colored
material.
Example 3 - SiO2-CaSiO3(2.5)-Pt(1.5)-Sn(0.9)
[0113] This catalyst was prepared in the same manner as Example 1, with the
following
starting materials: 0.26 g of CaSiO3 as a support modifier; 0.5 ml of
colloidal Si02 (15 wt.%
solution, NALCO), 0.3355 g (0.86 mmol) of Pt(NH3)4(NO3)2; and 0.2052 g (0.86
mmol) of
Sn(OAc)2. Yield: 10.90 g of dark grey material.
Example 4 - Si02 + MgSi03-Pt(1.0)-Sn(l.0)
[0114] This catalyst was prepared in the same manner as Example 1, with the
following
starting materials: 0.69 g of Mg(AcO) as a support modifier; 1.3 g of
colloidal Si02 (15 wt.%
solution, NALCO), 0.2680 g (0.86 mmol) of Pt(NH3)4(NO3)2i and 0.1640 g (0.86
mmol) of
Sn(OAc)2. Yield: 8.35 g. The Si02 support was impregnated with a solution of
Mg(AcO) and
colloidal Si02. The support was dried and then calcined to 700 C.
Example 5 - SiO2-CaSiQ,(5)-Re(4.5)-Pd(1)
[0115] The Si02-CaSiO3(5) modified catalyst support was prepared as described
in
Example 1. The Re/Pd catalyst was prepared then by impregnating the Si02-
CaSiO3(5) (1/16
inch extrudates) with an aqueous solution containing N144ReO4 and Pd(N03)2.
The metal
solutions were prepared by first adding NH4Re04 (0.7237 g, 2.70 mmol) to a
vial containing
12.0 ml of deionized H2O. The mixture was stirred for 15 min at room
temperature, and 0.1756
g (0.76 mmol) of solid Pd(N03)2 was then added. The mixture was stirred for
another 15 min
at room temperature, and then added drop wise to 10.0 g of dry Si02-
(0.05)CaSiO3 catalyst
support in a 100 ml round-bottomed flask. After completing the addition of the
metal solution,
the flask containing the impregnated catalyst was left standing at room
temperature for two
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WO 2011/053365 PCT/US2010/022947
hours. All other manipulations (drying, calcination) were carried out as
described in Example
1. Yield: 10.9 g of brown material.
Example 6 - Si02-ZnO(5 -Pt(1)-Sn(1)
[0116] Powdered and meshed high surface area silica NPSG SS61138 (100 g) of
uniform
particle size distribution of about 0.2 mm was dried at 120 C in a circulating
air oven
atmosphere overnight and then cooled to room temperature. To this was added a
solution of
zinc nitrate hexahydrate. The resulting slurry was dried in an oven gradually
heated to 110 C
(>2 hours, 10 C/min.) then calcined. To this was added a solution of platinum
nitrate
(Chempur) in distilled water and a solution of tin oxalate (Alfa Aesar) (1.74
g) in dilute nitric
acid (1N, 8.5 ml) The resulting slurry was dried in an oven gradually heated
to 110 C (>2
hours, 10 C/min.). The impregnated catalyst mixture was then calcined at 500 C
(6 hours,
1 C/min).
[0117] In addition, the following comparative catalysts were also prepared.
Example 7 - Comparative
[0118] Ti02-CaSiO3(5)-Pt(3)-Sn(l.8). The material was prepared by first adding
CaSiO3 to
the Ti02 catalyst (Anatase, 14/30 mesh) support, followed by the addition of
Pt/Sn as described
in Example 1. First, an aqueous suspension of CaSiO3 (<_ 200 mesh) was
prepared by adding
0.52 g of the solid to 7.0 ml of deionized H2O, followed by the addition of
1.0 ml of colloidal
Si02 (15 wt.% solution, NALCO). The suspension was stirred for 2 h at room
temperature and
then added to 10.0 g of Ti02 catalyst support (14/30 mesh) using incipient
wetness technique.
After standing for 2 hours, the material was evaporated to dryness, followed
by drying at 120 C
overnight under circulating air and calcination at 500 C for 6 hours. All of
the Ti02-CaSiO3
material was then used for Pt/Sn metal impregnation using 0.6711 g (1.73 mmol)
of
Pt(NH3)4(NO3)2 and 0.4104 g (1.73 mmol) of Sn(OAc)2 following the procedure
described in
Example 1. Yield: 11.5 g of light grey material.
Example 8 - Comparative
[0119] Sn(0.5) on High Purity Low Surface Area Silica. Powdered and meshed
high purity
low surface area silica (100 g) of uniform particle size distribution of about
0.2 mm was dried
at 120 C in an oven under nitrogen atmosphere overnight and then cooled to
room temperature.
To this was added a solution of tin oxalate (Alfa Aesar) (1.74 g) in dilute
nitric acid (1N, 8.5
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WO 2011/053365 PCT/US2010/022947
ml). The resulting slurry was dried in an oven gradually heated to 110 C (>2
hours,
C/min.). The impregnated catalyst mixture was then calcined at 500 C (6 hours,
1 C/min).
Example 9 - Comparative
[0120] Pt(2)-Sn(2) on High Surface Area Silica. Powdered and meshed high
surface area
silica NPSG SS61138 (100 g) of uniform particle size distribution of about 0.2
mm was dried at
120 C in a circulating air oven atmosphere overnight and then cooled to room
temperature. To
this was added a solution of nitrate hexahydrate (Chempur). The resulting
slurry was dried in
an oven gradually heated to 110 C (>2 hours, 10 C/min.) then calcined. To this
was added a
solution of platinum nitrate (Chempur) in distilled water and a solution of
tin oxalate (Alfa
Aesar) in dilute nitric acid. The resulting slurry was dried in an oven
gradually heated to 110 C
(>2 hours, 10 C/min.). The impregnated catalyst mixture was then calcined at
500 C (6 hours,
1 C/min).
Example 10 - Comparative
[0121] KA160-Pt(3)-Sn(1.8). The material was prepared by incipient wetness
impregnation
of KA160 catalyst support (Si02-(0.05) A1203, Sud Chemie, 14/30 mesh) as
described in
Example 16. The metal solutions were prepared by first adding Sn(OAc)2 (0.2040
g, 0.86
mmol) to a vial containing 4.75 ml of 1:1 diluted glacial acetic acid. The
mixture was stirred
for 15 min at room temperature, and then, 0.3350 g (0.86 mmol) of solid
Pt(NH3)4(NO3)2 were
added. The mixture was stirred for another 15 min at room temperature, and
then added drop
wise to 5.0 g of dry KA160 catalyst support (14/30 mesh) in a 100 ml round-
bottomed flask.
All other manipulations, drying and calcination was carried out as described
in Example 16.
Yield: 5.23 g of tan-colored material.
Example 11 - Comparative
[0122] Si02-SnO2(5)-Pt(1)-Zn(1). Powdered and meshed high surface area silica
NPSG
SS61138 (100 g) of uniform particle size distribution of about 0.2 mm was
dried at 120 C in a
circulating air oven atmosphere overnight and then cooled to room temperature.
To this was
added a solution of tin acetate (Sn(OAc)2). The resulting slurry was dried in
an oven gradually
heated to 110 C (>2 hours, 10 C/min.) then calcined. To this was added a
solution of platinum
nitrate (Chempur) in distilled water and a solution of tin oxalate (Alfa
Aesar) in dilute nitric
acid The resulting slurry was dried in an oven gradually heated to 110 C (>2
hours, 10 C/min.).
The impregnated catalyst mixture was then calcined at 500 C (6 hours, 1
C/min).
CA 02777754 2012-04-16
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Example 12 - Comparative
[0123] Si02-Ti02(10)-Pt(3)-Sn(1.8). The Ti02-modified silica support was
prepared as
follows. A solution of 4.15 g (14.6 mmol) of Ti{OCH(CH3)2}4 in 2-propanol (14
ml) was
added dropwise to 10.0 g of Si02 catalyst support (1/16 inch extrudates) in a
100 ml round-
bottomed flask. The flask was left standing for two hours at room temperature,
and then
evacuated to dryness using a rotor evaporator (bath temperature 80 C). Next,
20 ml of
deionized H2O was slowly added to the flask, and the material was left
standing for 15 min.
The resulting water/2-propanol was then removed by filtration, and the
addition of H2O was
repeated two more times. The final material was dried at 120 C overnight under
circulation air,
followed by calcination at 500 C for 6 hours. All of the Si02-TiO2 material
was then used for
Pt/Sn metal impregnation using 0.6711 g (1.73 mmol) of Pt(NH3)4(NO3)2 and
0.4104 g (1.73
mmol) of Sn(OAc)2 following the procedure described above for Example 1.
Yield: 11.98 g of
dark grey 1/16 inch extrudates.
Example 13 - Comparative
[0124] Si02-W03(10)-Pt(3)-Sn(1.8). The W03-modified silica support was
prepared as
follows. A solution of 1.24 g (0.42 mmol) of (NH4)6H2W12040 - n H2O, (AMT) in
deionized
H2O (14 ml) was added dropwise to 10.0 g of Si02 NPSGSS 61138catalyst support
(SA = 250
m2/g, 1/16 inch extrudates) in a 100 ml round-bottomed flask. The flask was
left standing for
two hours at room temperature, and then evacuated to dryness using a rotor
evaporator (bath
temperature 80 C). The resulting material was dried at 120 C overnight under
circulation air,
followed by calcination at 500 C for 6 hours. All of the (light yellow) Si02-
WO3 material was
then used for Pt/Sn metal impregnation using 0.6711 g (1.73 mmol) of
Pt(NH3)4(NO3)2 and
0.4104 g (1.73 mmol) of Sn(OAc)2 following the procedure described above for
Example 1.
Yield: 12.10 g of dark grey 1/16 inch extrudates.
Example 14 - Hydrogenation of Acetic Acid over Catalysts from Examples 1-13
and Gas
Chromatographic (GC) Analysis of the Crude Ethanol Product
[0125] Catalyst of Examples 1-13 were tested to determine the selectivity and
productivity
to ethanol as shown in Table 4.
[0126] The reaction feed liquid of acetic acid was evaporated and charged to
the reactor
along with hydrogen and helium as a carrier gas with an average combined gas
hourly space
31
CA 02777754 2012-04-16
WO 2011/053365 PCT/US2010/022947
velocity (GHSV), temperature, and pressure as indicated in Table 4. The feed
stream contained
a mole ratio hydrogen to acetic acid as indicated in Table 4.
[0127] The analysis of the products (crude ethanol composition) was carried
out by online
GC. A three channel compact GC equipped with one flame ionization detector
(FID) and 2
thermal conducting detectors (TCDs) was used to analyze the reactants and
products. The front
channel was equipped with an FID and a CP-Sil 5 (20 m) + WaxFFap (5 m) column
and was
used to quantify: Acetaldehyde; Ethanol; Acetone; Methyl acetate; Vinyl
acetate; Ethyl acetate;
Acetic acid; Ethylene glycol diacetate; Ethylene glycol; Ethylidene diacetate;
and Paraldehyde.
The middle channel was equipped with a TCD and Porabond Q column and was used
to
quantify: C02; ethylene; and ethane. The back channel was equipped with a TCD
and
Molsieve 5A column and was used to quantify: Helium; Hydrogen; Nitrogen;
Methane; and
Carbon monoxide.
[0128] Prior to reactions, the retention times of the different components
were determined
by spiking with individual compounds and the GCs were calibrated either with a
calibration gas
of known composition or with liquid solutions of known compositions. This
allowed the
determination of the response factors for the various components.
32
CA 02777754 2012-04-16
WO 2011/053365 PCT/US2010/022947
c N-000MC M\O\ON N00 N N
00 00 00 00 t~ N M M M d '* ' t N
M O N '=-1 00 d N M N O M M
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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
o o o L in in k r) in W) W') 'n tn vii W)
N N N \O \O \O \O N \O \O \O \O N \O \O \O
En
O O O O O v 0 0\ 0 0 0 n O k n 0 0
kn Wn kn In Ln N Ln in C'1 00 in N * t-- vl to
N N N N N N N N N N N N N N N N
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0 0 0 0 0 0 O o 0 0 0 0 0 0 0
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F~-I to kn 4 kn to to to kn V) kn kn
all
00
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un ~./ - 00 00
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33
CA 02777754 2012-04-16
WO 2011/053365 PCT/US2010/022947
Example 15 - Catalyst Stability( 15 hours)
[0129] Vaporized acetic acid and hydrogen were passed over a hydrogenation
catalyst of
the present invention comprising 3 wt.% Pt, 1.5 wt.% Sn and 5 wt.% CaSiO3, as
a promoter on
high purity, high surface area silica having a surface area of approximately
250 mz/g at a molar
ratio of hydrogen to acetic acid of about 5:1 (feed rate of 0.09 g/min HOAc;
160 sccm/min H2;
60 sccm/min N2) at a temperature of about 225 C, pressure of 200 psig (about
1400 KPag), and
GHSV = 6570 h-1. Si02 stabilized with 5% CaSiO3 in hydrogenation of acetic
acid was studied
in a run of 15 hours duration at 225 C using a fixed bed continuous reactor
system to produce
mainly ethanol, acetaldehyde, and ethyl acetate through hydrogenation and
esterification
reactions in a typical range of operating conditions employing 2.5 ml solid
catalyst (14/30
mesh, diluted 1:1 (v/v, with quartz chips, 14/30 mesh). FIG. 3A illustrates
the selectivity, and
FIG. 3B illustrates the productivity of the catalysts as a function of time on-
stream during the
initial portion of the catalysts life. From the results of this example as
reported in FIG. 3A and
FIG. 3B, it can be appreciated that it is possible to attain a selectivity of
over 90% and
productivity of over 500 g of ethanol per kilogram of catalyst per hour.
Example 16 - Catalyst Stability (over 100 hours)
[0130] Catalyst Stability: SiO2-CaSiO3(5)-Pt(3)-Sn(l.8). The catalytic
performance and
initial stability of SiO2-CaSiO3(5)-Pt(3)-Sn(1.8) was evaluated at constant
temperature (260 C)
over 100 hrs of reaction time. Only small changes in catalyst performance and
selectivity were
observed over the 100 hrs of total reaction time. Acetaldehyde appeared to be
the only side
product, and its concentration (-3 wt.%) remained largely unchanged over the
course of the
experiment. A summary of catalyst productivity and selectivity is provided in
FIGS. 4A and
4B.
Example 17 - Catalyst Stability
[0131] The procedure of Example 16 was repeated at a temperature of about 250
C. FIGS.
5A and 5B illustrate the productivity and selectivity of the catalysts as a
function of time on-
stream during the initial portion of the catalysts life. From the results of
this example, as
reported in FIGS. 5A and 5B, it can be appreciated, that it is still possible
to attain a selectivity
activity of over 90% but with productivity of over 800 g of ethanol per
kilogram of catalyst per
hour at this temperature.
34
CA 02777754 2012-04-16
WO 2011/053365 PCT/US2010/022947
Example 18
[0132] The catalyst of Example 3 was prepared with different loadings of
support modifier,
CaSiO3, and produced the following catalysts: (i) Si02-Pt(1.5)-Sn(0.9); (ii)
Si02-CaSiO3(2.5)-
Pt(1.5)-Sn(0.9); (iii) Si02-CaSiO3(5.0)-Pt(l.5)-Sn(0.9); (iv) Si02-CaSiO3(7.5)-
Pt(1.5)-Sn(0.9);
and (v) Si02-CaSiO3(10)-Pt(1.5)-Sn(O.9). Each catalyst was used in
hydrogenating acetic acid
at 250 C and 275 C under similar conditions, i.e., 1400 bar (200 psig), GHSV
of 2500 hr-' and
a 10:1 hydrogen to acetic acid molar feed ratio, (683 sccm/min of H2 to 0.183
g/min AcOH).
The conversion is shown in FIG. 6A, productivity in FIG. 6B, selectivity at
250 C in FIG. 6C
and selectivity at 275 C in FIG. 6D.
[0133] As shown in FIG. 6A, the conversion of acetic acid at 250 C and 275 C
surprisingly
increased at CaSiO3 loadings greater than 2.5 wt.%. The initial drop in
conversion exhibited
from 0 to 2.5 wt.% CaSiO3 would suggest that conversion would be expected to
decrease as
more CaSiO3 is added. This trend, however, surprisingly reserves as more
support modifier is
added. Increasing conversion also results in increased productivity, as shown
in FIG. 6B. The
selectivities in FIG. 6C and 6C show a slight increase as the amount of
support modifier
increases.
[0134] While the invention has been described in detail, modifications within
the spirit and
scope of the invention will be readily apparent to those of skill in the art.
In view of the
foregoing discussion, relevant knowledge in the art and references discussed
above in
connection with the Background and Detailed Description, the disclosures of
which are all
incorporated herein by reference. In addition, it should be understood that
aspects of the
invention and portions of various embodiments and various features recited
below and/or in the
appended claims may be combined or interchanged either in whole or in part. In
the, foregoing
descriptions of the various embodiments, those embodiments which refer to
another
embodiment may be appropriately combined with other embodiments as will be
appreciated by
one of skill in the art. Furthermore, those of ordinary skill in the art will
appreciate that the
foregoing description is by way of example only, and is not intended to limit
the invention.
