Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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VINYL ACETATE CATALYST COMPRISING
METALLIC PALLADIUM AND GOLD AND PREPARED UTILIZING SONICATION
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to new and improved catalysts comprising metallic
palladium and
gold, which are useful for the production of vinyl acetate by reaction of
ethylene oxygen and
acetic acid.
Description of the Related Art Including Information Disclosed Under 37 CFR
1.97 and 1.98
It is known to produce vinyl acetate by reaction of ethylene, oxygen and
acetic acid using
a catalyst comprising palladium and gold, supported on a carrier. While the
process utilizing
such a catalyst is capable of producing vinyl acetate at relatively high
levels of productivity, any
expedient which could possibly result in even greater productivity or a
reduction in byproducts
would be very desirable.
The following references may be considered material to the invention claimed
herein.
U.S. Patents Nos. 3,775,342 issued November 27, 1973, and 3,822,308 issued
July 2,
1974, both to Kronig et al., each discloses a method of making vinyl acetate
catalysts comprising
2 0 treating a support simultaneously or successively with a solution A
containing dissolved salts of
noble metals such as palladium and gold and a solution B containing compounds
able to react on
the support with the noble metal salts to form water-insoluble compounds,
treating such water-
insoluble compounds with a reducing agent to convert the water-insoluble noble
metal
compounds to the free metals, washing the catalyst to remove water-soluble
compounds, and
2 5 applying an alkali metal compound, e.g., an alkali metal carboxylate
before or after treatment
with the reducing agent. Solution A can optionally also contain salts of other
metals such as
magnesium, calcium, barium and copper.
U.S. Patent No. 5,322,710, issued July 26, 1994, to Nicolau et al., discloses
a method of
preparing a catalyst useful for the production of vinyl acetate by reaction of
ethylene, oxygen
3 0 and acetic acid, comprising impregnating a porous support with water
soluble salts of palladium
and gold, fixing the palladium and gold as insoluble compounds on the support
by immersing
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and tumbling the impregnated support in a reactive solution for at least '/2
hour to precipitate
such compounds, and subsequently reducing the compounds to free metallic form.
U.S. Patent No. 5,347,046, issued September 13, 1994 to White et al.,
discloses catalysts
for the production of vinyl acetate by reaction of ethylene, oxygen, and
acetic acid, comprising a
palladium group metal and/or a compound thereof, gold and/or a compound
thereof, and copper,
nickel, cobalt, iron, manganese, lead or silver, or a compound thereof,
preferably deposited on a
support material.
Suslick, K.B., "Organometallic Sonochemistry," Advances in Organometallic
Chemistry
25, 73-119 (1986) is a general article on the application of ultrasound waves
to organometallic
reactions.
Suslick, K.S.; Fang, M.; Hyeon, T.; and Cichowlas, A.A., "Nanostructured Fe-Co
Catalysts Generated by Ultrasound," Materials Research Society S~m~osia
Proceedings. 351,
443-448 (1994), discuss the preparation and activity of Fe-Co catalysts
generated with
ultrasound waves.
Okitsu, K.; Bandow, H.; and Maeda, Y.; "Sonochemical Preparation of Ultrafine
Palladium Particles," Chemistry of Materials 8, 315-317 (1996) discuss the
sonochemical
reduction of Pd (II) to produce ultrafine Pd particles and state that
colloidal dispersion of these
particles "exhibit interesting catalytic activity."
2 o BRIEF SUMMARY OF THE INVENTION
In accordance with this invention, a catalyst effective for the production of
vinyl acetate
by reaction of ethylene, oxygen and acetic acid, comprising a porous support
on the porous
surfaces of which is deposited catalytically effective amounts of metallic
palladium and gold,
and optionally, one or more additional catalytically active metals such as
copper, is prepared by
2 5 steps comprising impregnating the support with one or more aqueous
solutions of water-soluble
compounds of the metals, fixing the metals on the support as water-insoluble
compounds in one
or more fixing steps by reaction with an appropriate alkaline compound, at
least one of such
fixing steps being carried out in a solution of the alkaline compound in which
the impregnated
support is immersed, while sonicating, i.e., applying ultrasound waves to,
such solution, and
3 0 reducing the water-insoluble compounds of the catalytically active metals
to their free metallic
form.
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Catalysts may be prepared by the method of this invention utilizing sonication
in the
fixing step, which are capable of implementing the production of vinyl acetate
by reaction of
ethylene, oxygen and acetic acid with relatively low selectivities to CO~
and/or heavy ends such
that the use of such catalysts may result in greater vinyl acetate
productivity than when any of
various catalysts known in the art is employed.
DETAILED DESCRIPTION OF THE INVENTION
In preparing the catalysts under this invention, the catalyst support material
is composed
of particles having any of various regular or irregular shapes, such as
spheres, tablets, cylinders,
rings, stars, or other shapes, and may have dimensions such as diameter,
length, or width of
about 1 to about 10 mm., preferably about 3 to 9 mm. Spheres having a diameter
of about 4 to
about 8 mm. are preferred. The support material may be composed of any
suitable porous
substance, e.g., silica, alumina, silica-alumina, titania, zirconia,
silicates, aluminosilicates,
titanates, spinel, silicon carbide, or carbon and the like.
The support material may have a surface area within the range, for example, of
about 10
to about 350, preferably about 100 to about 200 m'-/g, an average pore size in
the range, for
example, of about 50 to about 2000 angstroms, and a pore volume in the range,
for example, of
about 0.1 to 2, preferably about 0.4 to about 1.2 ml/g.
In the preparation of the catalysts of this invention, the support material
may be treated to
2 0 deposit catalytic amounts of palladium, gold, and any additional
catalytically active metal, if
any, on the porous surfaces of the support particles. Any of various methods
for accomplishing
this purpose may be used, all of which involve simultaneous or separate
impregnations of the
support with one or more aqueous solutions of water-soluble compounds of the
catalytically
active metals. Palladium(II)chloride, sodium palladium(II)chloride, potassium
2 5 palladium(II)chloride, palladium(II)nitrate or palladium(II)sulfate are
examples of suitable
water-soluble palladium compounds; an alkali metal, e.g., sodium or potassium
salt of
auric(III)chloride or tetrachloroauric(III)acid can be used as the water-
soluble gold compound;
and, if, for example, copper is utilized as an additional catalytically active
metal, cupric nitrate
trihydrate or hexahydrate, cupric chloride (anhydrous or dihydrate), cupric
acetate monohydrate,
3 0 cupric sulfate (anhydrous or pentahydrate), cupric bromide, or cupric
formate (anhydrous or
tetrahydrate), can be used as the water-soluble copper compound. An alkali
metal salt of
tetrachloroauric(III)acid, sodium palladium(II)chloride and cupric nitrate
trihydrate or cupric
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chloride are preferred salts for impregnation of gold, palladium and copper
respectively because
of their good water solubility.
In preparing the catalyst, the impregnations of the support material with
solutions of
water-soluble salts of the catalytically active metals may be effected by any
method known to
those skilled in the art. Preferably, however, such impregnations are
accomplished by the
"incipient wetness" method wherein an amount of water-soluble salt solution
used for the
impregnation is from about 95 to about 100 percent of the absorptive capacity
of the support
material. The concentration of the solution or solutions is such that the
amounts of catalytically
active metals in the solution or solutions absorbed on the support is equal to
a desired
predetermined amount. If more than one such impregnation is carried out, then
each
impregnation may contain water-soluble compound equivalent to all or only a
portion of the
amount of one or any combination of the catalytically active metals desired in
the final catalyst,
as long as the amounts of such metals in the total of the impregnating
solutions absorbed are
equal to the final desired amounts. The impregnations are such as to provide,
for example, about
1 to about 10 grams of elemental palladium; for example, about 0.5 to about 10
grams of
elemental gold; and, for example, if copper is utilized as an additional
catalytically active metal,
about 0.5 to about 3.0 grams of elemental copper per liter of finished
catalyst, with the amount
of gold being from about 10 to about 125 weight percent based on the weight of
palladium.
After each impregnation of the support with an aqueous solution of at least
one water-
2 0 soluble salt of a catalytically active metal, the metal is "fixed," i.e.,
precipitated, as a water-
insoluble compound such as the hydroxide, by reaction with an appropriate
alkaline compound,
e.g., an alkali metal hydroxide, silicate, borate, carbonate or bicarbonate,
in aqueous solution.
Sodium and potassium hydroxides are preferred alkaline fixing compounds. The
alkaline
compound should be in an amount of, for example, about 1 to about 2,
preferably about 1.1. to
2 5 about 1.8 times the amount necessary to completely precipitate the cations
of the catalytically
active metals present in the water-soluble salts. At least one of such fixing
steps is accomplished
with the aid of sonication, i.e., the application of ultrasound waves to a.
solution of the alkaline
fixing compound in which is immersed the support material impregnated with at
least one water-
soluble salt of a catalytically active metal.
3 0 In catalyst preparations including more than one fixing step, one or all
of the fixing steps
may be carried out utilizing sonication. However, if less than all of the
fixing steps employ
sonication, then the fixing steps other than those employing sonication may be
done by the
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incipient wetness method wherein the impregnated support is dried, e.g., at a
temperature of
about 150~C for one hour, contacted with an amount of solution of the alkaline
material equal to
about 95-100% of the pore volume of the support, and allowed to stand for a
period of about'/2
hour to about 16 hours; or the roto-immersion method wherein the impregnated
support without
drying is immersed in a solution of the alkaline material and is rotated
and/or tumbled during at
least the initial period of precipitation such that a thin band of the
precipitated water-soluble
compound is formed at or near the surface of the support particles. In
carrying out the fixing of
metals by roto-immersion, the rotation and tumbling may be carried out, for
example, at about 1
to about 10 rpm for a period of, for example, at least about 0.5 hour,
preferably about 0.5 to
about 4 hours. The contemplated roto-immersion method is disclosed in
previously cited U.S.
Patent No. 5,332,710, the entire disclosure of which is incorporated herein by
reference.
The fixed, i.e. precipitated compounds of palladium, gold, other catalytically
active
metals, if any, such as copper, may be reduced, for example, in the vapor
phase with ethylene,
e.g., about 5% in nitrogen at about 150°C for about 5 hours after first
washing the catalyst
containing the fixed metal compounds, until it is free of anions such as
halide, and drying, e.g.,
at about 150~C for about I hour, or such reduction may be accomplished before
washing and
drying in the liquid phase at room temperature with sonication with an aqueous
solution of
hydrazine hydrate wherein the excess of hydrazine over that required to reduce
all the metal
compounds present on the support is in the range, for example, of about 8: I
to about 15:1,
2 0 followed by washing drying. Other reducing agents and means for reducing
the fixed metal
compounds present on the support may be employed as conventional in the art.
The reduction of
the fixed palladium, gold and other metal compounds, if any, mainly results in
the formation of
the free metal, although a minor amount of metal oxide may also be present. In
preparations
using more than one impregnation and fixing steps, the reduction may be
carried out after each
2 5 fixing step or after the total of the metallic elements have been fixed on
the support. In addition
to being utilized in one or more fixing steps as described previously,
sonication may also be
utilized in one or more reduction steps, e.g., by applying the sonication to
water containing
immersed therein the catalyst support containing the fixed (water-insoluble)
metal compounds
and through which is bubbled 5% ethylene in nitrogen, or the sonication may be
applied to an
3 0 aqueous solution of hydrazine hydrate containing immersed therein the
catalyst support
containing the fixed metal compounds.
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A simple example of carrying out the foregoing catalyst preparation includes a
single
impregnation of the support with water soluble salts such that the impregnated
support contains
the palladium and gold desired in the final catalyst, a single fixing step by
immersing the
impregnated support in a solution of the alkaline compound while applying
sonication to the
solution, and a single reducing step whereby the fixed palladium and gold are
reduced to their
free metallic form.
As another example of foregoing general procedure, a "separate fix" method may
be used
to fix the catalytically active metallic elements on the support and reduce
the water-insoluble
metal compounds to the desirable free metallic form. In this method, using the
specific
procedures described previously, the support is first impregnated with an
aqueous solution of a
water-soluble compound of palladium and of any additional catalytically active
metal, if any,
other than gold, e.g. copper, by incipient wetness, and the palladium, and
additional metal, if
present, are then fixed by treatment with an alkaline fixing solution
utilizing sonication. The
catalyst is then dried and separately impregnated with a solution of a soluble
gold compound
having the amount of elemental gold desired in the catalyst, and the gold is
fixed by treatment
with an alkaline fixing solution by sonication. If a hydrocarbon such as
ethylene, or hydrogen is
to be used in the vapor phase as reducing agent, the catalyst containing the
fixed metal
compounds is washed until it is free of dissolved anions, dried , and reduced
with ethylene or
other hydrocarbon, or hydrogen, as previously described. If hydrazine is to be
used in the liquid
2 o phase as reducing agent, the catalyst containing the fixed metal compounds
is treated with an
aqueous solution of excess hydrazine hydrate with sonication before washing
and drying to
reduce the metal compounds to the free metals, and the catalyst is then washed
and dried as
described. Sonication may be utilized in the reduction step as described
previously.
After the catalyst containing palladium, gold and any additional catalytically
active
2 5 metal, if any, e.g., copper, in a free metallic form, deposited on a
support material, is prepared by
any of the foregoing methods, it is advantageously further impregnated with a
solution of an
alkali metal acetate, preferably potassium or sodium acetate, and most
preferably potassium
acetate. The catalyst is then dried such that the finished catalyst contains,
for example, about 10
to about 70, preferably about 20 to about 60 grams of alkali metal per liter
of finished catalyst.
3 0 When vinyl acetate is prepared using a catalyst according to the present
invention, a
stream of gas, which contains ethylene, oxygen or air, acetic acid, and
desirably an alkali metal
acetate, is passed over the catalyst. The composition of the gas stream can be
varied within wide
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limits, taking into account explosive limits. For example, the molar ratio of
ethylene to oxygen
can be about 80:20 to about 98:2, the molar ratio of acetic acid to ethylene
can be about 2:1 to
about 1:10, preferably about 1:1 to about 1:5, and the content of gaseous
alkali metal acetate can
be about 1-100 ppm, relative to the acetic acid employed. The alkali metal
acetate may be
conveniently added to the feed stream as a spray of an aqueous solution of
such acetate. The gas
stream also can contain other inert gases, such as nitrogen, carbon dioxide
and/or saturated
hydrocarbons. Reaction temperatures which can be used are elevated
temperatures, preferably
those in the range of about 150-220~C. The pressure employed can be a somewhat
reduced
pressure, normal pressure or elevated pressure, preferably a pressure of up to
about 20
atmospheres gauge.
The following non-limiting examples further illustrate the invention. In each
example,
the sonication was carried out in a 250-ml round bottom sonication flask
(Misonix) with three
24/40 side necks using an XL2020 Sonicator Programmable Ultrasonic Processor
(Misonix)
fitted with a flat-tipped tapped disrupter horn (titanium alloy, 3/4"
diameter). The ultrasound
waves emitted by the sonicator had a frequency of about 20 kHz. Sonication was
carried out for
about 1 hour to about 20 hours. The sonication may be effected by any of the
various types of
sonicators known in the art, several of which are commercially available. The
support material
for the catalyst consisted of Sud Chemie KA-160 silica spheres having a
nominal diameter of 5
mm., a surface area of about 160 to 175 m2/g, and a pore volume of about 0.68
ml/g.
EXAMPLES
Example 1
100 cc of the 5 mm silica support material for the catalyst was measured into
a 500-ml
round bottom flask. In a 100-ml graduated cylinder, aqueous Na,PdCl4 (7 g Pd/1
support),
2 5 aqueous NaAuCl4 (4 g Au/1 support), and deionized water were added to
produce a total solution
volume equal to the total volume the support could absorb. The Pd/Au-
containing solution was
poured into the silica support to impregnate the support to incipient wetness,
and the support was
shaken for approximately 5 minutes to ensure complete absorption of the
solution. The treated
support was then poured into a 250-ml sonication flask containing 114 cc of
aqueous NaOH
3 0 (from 50% w/w NaOH/H~O, 120% of the amount of NaOH needed to convert the
metal salts to
their hydroxides). The flask was immediately placed on the sonicator to
sonicate for 1 hour at
level 2. The solution was drained from the treated support, and the treated
support was poured in
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a 500-ml graduated cylinder with dip tube to wash with a continuous flow of
deionized water for
hours. The effluent was tested with AgN03 to detect the presence of chlorides
via formation of
insoluble AgCI. The effluent was drained from the treated support, and the
treated support was
transferred to a 500-ml round bottom flask. The flask was placed in an oven,
and the treated
5 support was dried overnight at 150 ° C under constant N~ purge. The
metal hydroxides were
reduced with 5% CZH4 in NZ at a flow rate of 0.5 SCFH at 150°C for 5
hours. KOAc (40 g/1
support) and deionized water were added to a 100-ml graduated cylinder to
produce a solution
volume equal to the amount of solution the support would absorb. The treated
support was
impregnated by incipient wetness with the aqueous KOAc and let stand for 15
minutes. The
catalyst was transferred to a fluid-bed dryer to dry for 1 hour at 100
° C.
Example 2
The procedure of Example 1 was followed through sonication at level 2 for 1
hour.
3.0 ml of hydrazine hydrate, NZH4~H~O was added to the NaOH solution (large
excess of the
amount necessary to reduce the metal hydroxides to the metals), and the
sonication was
continued at level 2 for 1 hour. After sonication, the washing, drying,
reduction, and
impregnation with KOAc were carried out following the procedure of Example 1.
Example 3
2 0 100 cc of the 5 mm silica catalyst support material was measured into a
500-ml bottom
flask. In a 100-ml graduated cylinder, aqueous Na~PdCl4 (7 g Pd/1 support),
aqueous NaAuCl4
(4 g Au/1 support), CuCl2 (0.9264 g/1 support), and deionized water were added
to produce a
total solution volume equal to the total volume the support could absorb. The
Pd/Au/Cu-
containing solution was poured into the silica support to impregnate the
support by incipient
2 5 wetness, and the support was shaken for approximately 5 minutes to ensure
complete absorption
of the solution. The treated support was then poured into a 250-ml sonication
flask containing
114 cc of aqueous NaOH (from 50% w/w NaOH/H,O, 120% of the amount needed to
convert
the metal salts to their hydroxides). The flask was immediately placed on the
sonicator for 1
hour at level 2. After sonication, the washing, drying, reduction, and
impregnation with KOA°
3 0 were carried out following the procedure of Example 1.
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Example 4
100 cc of the 5 mm silica catalyst support material was measured into a 500-ml
round
bottom flask. In a 100-ml graduated cylinder, aqueous Na~PdCl4 (7 g Pd/1
support), CuCh
(0.9264 g Cu/1 support), and deionized water were added to produce a total
solution volume
equal to the total volume the support could absorb. The Pd/Cu-containing
solution was poured
into the silica support to impregnate the support by incipient wetness, and
the support was
shaken for approximately 5 minutes to ensure complete absorption of the
solution. The treated
support was then poured into a 250-ml sonication flask containing 114 cc of
aqueous NaOH
(from 50% w/w NaOH/H~O, 120% of the amount needed to convert the metal salts
to their
hydroxides). The flask was immediately placed on the sonicator to sonicate for
1 hour at level 2.
After sonication, the solution was drained from the treated support, and the
support was dried on
a fluid-bed dryer at 100°C for 1 hour. In a 100-ml graduated cylinder,
aqueous NaAuCl4 (4 g
Au/1 support), NaOH (as 50% w/w NaOH/H20, 180% of the amount needed to convert
the Au
salt to its hydroxide), and deionized water were added to produce a total
solution volume equal
to the amount of solution the support could absorb. The solution was allowed
to stand for up to
one hour before being added to the treated support to avoid precipitation of
the Au hydroxide.
The treated support was impregnated by incipient wetness with the Au/NaOH-
containing
solution, and it was shaken for approximately 5 minutes to ensure complete
absorption of the
solution. The treated support was allowed to stand for 16 hours, then it was
poured in a 500-ml
2 0 graduated cylinder with a dip tube. The washing, drying, reduction, and
impregnation with
KOAc were carried out following the procedure of Example 1.
Example 5
The procedure of Example 1 was followed up through washing of the catalyst for
5 hours
2 5 in a 500-ml graduated cylinder with a dip tube. After washing, the
effluent was drained from the
treated support, and the support was transferred to a sonication flask, and
approximately
114 cc of deionized H~0 was added with 4.71 ml of N~H4H20 ( 1200% of the
amount necessary to
reduce the metal hydroxides to the metals). The solution was sonicated for 1
hour at level 2.
The flask was removed from the sonicator, and the excess solution was drained
from the treated
3 0 support. After 30 minutes, the treated support was rinsed with deionized
H20 several times to
remove excess hydrazine. The treated support was poured into a 500-ml
graduated cylinder with
a dip tube and washed continuously with deionized H,O for 35 minutes. The
treated support was
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transferred to a round bottom flask and dried overnight under constant NZ
purge. The reduction
and impregnation with KOAc were carried out following the procedure of Example
1.
5 Example 6
The procedure of Example 1 was followed except that the sonication was carried
out for
3.5 hours at level 2.
Example 7
10 The procedure of Example 1 was followed up through washing the catalyst for
5 hours in
a 500-ml graduated cylinder with a dip tube. After washing, the effluent was
drained from the
treated support, and the support was placed in a round bottom flask to dry
overnight at 150°C.
The treated support was transferred to a sonication flask, and approximately
114 cc of deionized
H20 was added with 4.71 ml of N~H4 H,O (approximately 1200% of the amount
necessary to
reduce the metal hydroxides to the metals). The solution was sonicated at
level 2 for 3 hours.
The flask was removed from the sonicator, and the excess solution was drained
from the treated
support. The treated support was rinsed with deionized H,O several times to
remove excess
NZH4. The treated support was poured into a 500-ml graduated cylinder with a
dip tube and
washed continuously with deionized H,O for 3 hours and 15 minutes. The treated
support was
2 0 transferred to a fluid bed dryer and dried for 1 hour at 100 ° C.
The reduction and impregnation
with KOAc were carried out following the procedure of Example 1.
Example 8
The procedure of Example 1 was followed, except that the sonication was
carried out for
2 5 16 hours at level 2.
Example 9
The procedure of Example 1 was followed, except that the sonication was
carried out for
1 hour at level 2, and the support was impregnated to 95% by incipient
wetness.
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Example 10
The procedure of Example 1 was followed, except that the sonication was
carried out for
1 hour at level 4 and the support was impregnated to 95% by incipient wetness.
Example 11
100 cc of the 5 mm silica catalyst support material was measured into a 500-ml
round
bottom flask. In a 100-ml graduated cylinder, aqueous Na,PdCl4 (7 g Pd/1
support) and
deionized water were added to produce a total solution volume equal to the
total volume the
support could absorb. The Pd-containing solution was poured into the silica
support to
impregnate the support by incipient wetness, and the support was shaken for
approximately
5 minutes to ensure complete absorption of the solution. The treated support
was then poured
into a 250-ml sonication flask containing 114 cc of aqueous NaOH (from 50% w/w
NaOH/H~O,
120% of the amount needed to convert the metal salts to their hydroxides). The
flask was
immediately placed on the sonicator to sonicate for 1 hour at level 4. The
solution was drained
from the treated support, and the treated support was poured in a 500-ml
graduated cylinder with
a dip tube to wash with a continuous flow of deionized water for 1 hour. The
catalyst was left
overnight, and the washing was continued for 3 hours and 45 minutes. The
effluent was tested
with AgN03 to detect the presence of chlorides via formation of insoluble
AgCI. The effluent
was drained from the treated support, and the treated support was transferred
to a fluid bed dryer
to dry at 100°C for 1 hour. In a 100-ml graduated cylinder, aqueous
NaAuCl4 (7 g Au/I support)
and deionized water were added to produce a total solution volume equal to the
total volume the
support could absorb. The Au-containing solution was poured into the Pd-
containing silica
support to impregnate the support by incipient wetness, and the support was
shaken for
approximately 5 minutes to ensure complete absorption of the solution. The
treated support was
2 5 then poured into a 250-ml sonication flask containing 114 cc of aqueous
NaOH (from 50% w/w
NaOH/HZO, 180% of the amount needed to convert the metal salts to their
hydroxides). The
flask was drained from the treated support, and the treated support was poured
in a 500-ml
graduated cylinder with a dip tube to wash with continuous flow of deionized
water for 5 hours.
The effluent was tested with AgNO; to detect the presence of chlorides via
formation of
3 0 insoluble AgCI. The effluent was drained from the treated support, and the
treated support was
transferred to a 500-ml round bottom flask. The flask was placed in an oven,
and the treated
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12
support was dried overnight at 150°C under constant N~ purge. The
reduction and impregnation
with KOAc were carried out following the procedure of Example 1.
Example 12
The procedure of Example 4 was followed, except that the sonication was
carried out for
1 hour at level 4.
Example 13
The procedure of Example 4 was followed , except that the amount of Cu from
CuClz
was 2.084 g/1 support, and the sonication was carried out for 1 hour at level
4.
Example 14
The procedure of Example 1 was followed, except that the sonication was
carried out for
1 hour at level 3 and the catalyst was dried (after washing) on a fluid-bed
dryer at 100°C for 1
hour instead of in an oven at 150°C under constant Nz purge.
Example 15
The procedure of Example 1 was followed, except that the amount of Pd from
Na~PdCl4
was 9.844 g/1 and the amount of the Au from NaAuCl4 was 5.625 g/1; the
sonication was carried
2 0 out for 1 hour at level 2; and the catalyst was dried (after washing) on a
fluid-bed dryer at 100 ° C
for 1 hour instead of in an oven at 150 ° C under constant N~ purge.
Example 16
The procedure of Example 11 was followed, except that the amount of Au from
NaAuCl4
2 5 was 4 g/1 and the sonications were carried out for 1 hour at level 2.
The catalysts of the examples were tested for their selectivity to various
byproducts in the
production of vinyl acetate by reaction of ethylene, oxygen and acetic. This
was accomplished
3 0 using the Vinyl Acetate Micro Unit (VAMU) which is a plug flow reactor run
at a temperature
sufficient to effect an oxygen conversion of 45%. The VAMU reactor is a 3 ft-
long. 16 mm i.d.
stainless steel tube with a 3 mm concentric thermocouple well. The reactor is
equipped with a
CA 02389448 2002-04-29
WO 01/36091 PCT/US00/28723
13
heating jacket or "shell" through which hot water and steam are circulated. A
30 cc sample of
catalyst is diluted with support up to 150 cc and loaded to the reactor. The
catalyst/support
mixture is topped with 30 cc of support. After a single pass-through of the
oxygen, ethylene and
acetic acid in a Nitrogen dilutent, at either constant temperature or constant
oxygen conversion,
the products were analyzed by gas-phase chromatography.
Table I shows for each example details of the method of malting the catalyst
and its
make-up, in terms of the nominal amounts, i.e. total of the catalytically
active metals Pd, Au, and
optionally Cu, impregnated onto the support (Metal Content of Catalyst,
Nominal Amount), the
percentage of the amount of each metal initially impregnated onto the support
and retained in the
final catalyst (Metal Content of Catalyst, % Retention), the intensity level
of sonication applied
to each fixing of the metals on the catalyst (Sonication, Level), the period
of time of such fixing
(Sonication, t., hr.), and the reducing agent (Red. Agent) used for the
reduction, and details of
the process of synthesizing VA from the components of the gaseous feed in
terms of the
selectivity to COZ and heavy ends (HE), the temperature of the shell or jacket
(Shell Temp., ~C)
to achieve close to 45% oxygen conversion, and the specific measured percent
oxygen
conversion (OZ Conv, %).
CA 02389448 2002-04-29
WO 01/36091 PCT/US00/28723
14
TABLE I
VAMU UNIT PERFORMANCE DATA FOR CATALYST
> O O ~n .-~oo N N O~ ~i'~n N N ~n N M
O v7 W n ~n ~ W v0W O ~ W O ~n v1 ~n
o Wit'<t V ~ V' O d'd' ~ ~ V' ~ ~t
V
I M M O~ ~ V'1Q1 ~ O~ ~ V7 .-~~!1l~ I~ V'1
:y,
U o; ~ t~ ci ~c oo r;M oo v, o ~t tW d- t~
~ r ~, ~ ct ~n ~n ~ W ~t ~ v-,~ ~ ~t m
w D
H
[~ [~ ~ V~ O1 O O l~ M U o0 O ~O O
W N N O O ~O V Wit'00 ~n O~ O~ O~ O~ Do ~O
~ 00 V7 l~ O Wn \O \OW l~ 00 f~ 00 00 O ~O
y ,., O O O O O O O O O O O O O O
.y
U
N
_ ~ V'1O ~!1~ O ~O ~O~ N I~ M ~ O~ O M
N Q N v0 O v1 ~n c~ Ov O O~ t~ 00 ~ .- mn
V7 U ~ oo ~ ~i os oo ~ ~ ~i ~ v-;~; ~ 00
x x x x x x x,x ~ x x x z, x x
C~ U z U U z U~ z U U~ U U U~ U U U
Q
...,. M
O '~ M
U
N N N N N N N N N '~t~' ~t ~ M N
, M ~O ~ ~ ~ ~ i ~ i W i i
U , ~ ~ . . . . . . . . ~
~
c
0
r M ~O \O M V'1 ~ O l~ ~ O1 n O V7 M
M ~ll~ l~ M ~ M M M I~ M ~ O~ ~ll~!'1
>, o
'd O ~ O O ~O O~ O~O N c0 N m1'
U
0
C ~ ~ , ~ N N i ~ ~ i ~ ~ i N ~ i i
cJ U , . ~ ~ . . . . . . . ~ o
~ ~ O O O N
O
U
O ,n
~ ~?'Wit'V ~I'~ d' Wit'~ ~ d' !~ ~ ~h
Q
cd
C
O
z
;
N M ~ v W t~oo O~ O N c~ ~ ~n
W O
CA 02389448 2002-04-29
WO 01/36091 PCT/US00/28723
The results shown in Table I establish that the supported Pd and Au containing
catalysts
prepared by a method utilizing sonication in the fixing step are effective in
the production of VA
by reaction of ethylene, oxygen and acetic acid. In particular, the results of
Examples 1,3, 4, 9,
10, 12, 13, and 14 show that the catalyst made by the method of this invention
is capable of
catalyzing the reaction with a CO~ selectivity below that resulting from the
use of prior art
catalysts, for example, Bayer VA catalysts of the type described in GB
1,246,015 and US
5,700,753; incorporated by reference herein. VAMU unit performance data for
Bayer catalyst
was found to be:
%CO~ selectivity : 6.54
%HE selectivity : 0.652
%Oxygen Conversion : 45.3
