U.S. patent application number 09/315938 was filed with the patent office on 2001-12-06 for catalyst and use thereof in the production of vinyl acetate.
Invention is credited to KITCHEN, SIMON JAMES, QIN, DAIYI.
Application Number | 20010049335 09/315938 |
Document ID | / |
Family ID | 10832459 |
Filed Date | 2001-12-06 |
United States Patent
Application |
20010049335 |
Kind Code |
A1 |
KITCHEN, SIMON JAMES ; et
al. |
December 6, 2001 |
CATALYST AND USE THEREOF IN THE PRODUCTION OF VINYL ACETATE
Abstract
A catalyst for use in the production of vinyl acetate which
comprises (1) a catalyst support, (2) palladium, (3) an acid, (4)
at least one acetic acid catalyst promoter and (5) at least one
vinyl acetate promoter and/or co-promoter. A process for the
production of vinyl acetate from ethylene and an oxygen-containing
gas using the catalyst.
Inventors: |
KITCHEN, SIMON JAMES;
(HILLAM, GB) ; QIN, DAIYI; (CHENGDU, CN) |
Correspondence
Address: |
NIXON & VANDERHYE P C
1100 N GLEBE ROAD
8TH FLOOR
ARLINGTON
VA
22201
|
Family ID: |
10832459 |
Appl. No.: |
09/315938 |
Filed: |
May 21, 1999 |
Current U.S.
Class: |
502/305 ;
502/313; 502/314; 502/315; 502/317; 502/318; 502/319; 502/321;
502/322; 502/325; 502/326; 502/327; 502/328; 502/333; 502/335;
502/337; 502/339; 502/340; 502/344; 502/349; 502/350; 502/353;
560/208 |
Current CPC
Class: |
B01J 23/66 20130101;
B01J 23/52 20130101; B01J 23/44 20130101; B01J 23/58 20130101; C07C
67/055 20130101; B01J 23/56 20130101; C07C 67/055 20130101; C07C
69/01 20130101; C07C 67/055 20130101; C07C 69/15 20130101 |
Class at
Publication: |
502/305 ;
502/313; 502/314; 502/315; 502/317; 502/318; 502/319; 502/321;
502/322; 502/337; 502/344; 502/328; 502/325; 502/326; 502/327;
502/333; 502/335; 502/339; 502/340; 502/349; 502/350; 502/353;
560/208 |
International
Class: |
C07C 067/00; B01J
023/40 |
Foreign Application Data
Date |
Code |
Application Number |
May 22, 1998 |
GB |
9810928.3 |
Claims
We claim:
1. A catalyst for use in the production of vinyl acetate which
comprises (1) a catalyst support, (2) palladium, (3) an acid, (4)
at least one acetic acid catalyst promoter, and (5) at least one
vinyl acetate promoter and/or co-promoter.
2. A catalyst as claimed in claim 1 in which the support comprises
porous silica, alumina, silica/alumina, titania, zirconia or
carbon.
3. A catalyst as claimed in claim 1 in which the acid is a strong
acid selected from a heteropolyacid.
4. A catalyst as claimed in claim 2 in which the acid is a strong
acid selected from a heteropolyacid.
5. A catalyst as claimed in claim 3 in which the acid content is up
to 50% by weight.
6. A catalyst as claimed in claim 4 in which the acid content is up
to 50% by weight.
7. A catalyst as claimed in claim 1 in which the acetic acid
catalyst promoter is selected from selenium, titanium, tellurium
and/or vanadium-containing compounds.
8. A catalyst as claimed in 2 in which the acetic acid catalyst
promoter is selected from selenium, titanium, tellurium and/or
vanadium-containing compounds.
9. A catalyst as claimed in claim 3 in which the acetic acid
catalyst promoter is selected from selenium, titanium, tellurium
and/or vanadium-containing compounds.
10. A catalyst as claimed in claim 7 in which the acetic acid
catalyst promoter is an oxide, acetate or acetylacetonate.
11. A catalyst as claimed in claim 8 in which the acetic acid
catalyst promoter is an oxide, acetate or acetylacetonate.
12. A catalyst as claimed in claim 9 in which the acetic acid
catalyst promoter is an oxide, acetate or acetylacetonate.
13. A catalyst as claimed in claim 1 in which the vinyl acetate
catalyst promoter is selected from cadmium acetate, gold, copper
and nickel.
14. A catalyst as claimed in claim 2 in which the vinyl acetate
catalyst promoter is selected from cadmium acetate, gold, copper
and nickel.
15. A catalyst as claimed in claim 3 in which the vinyl acetate
catalyst promoter is selected from cadmium acetate, gold, copper
and nickel.
16. A catalyst as claimed in claim 7 in which the vinyl acetate
catalyst promoter is selected from cadmium acetate, gold, copper
and nickel.
17. A catalyst as claimed in claim 10 in which the vinyl acetate
catalyst promoter is selected from cadmium acetate, gold, copper
and nickel.
18. A catalyst as claimed in claim 13 in which the vinyl acetate
catalyst promoter is gold.
19. A catalyst as claimed in claim 1 in which the vinyl acetate
catalyst co-promoter is selected from alkali or alkali earth metal
salts.
20. A catalyst as claimed in claim 19 in which the vinyl acetate
co-promoter is sodium acetate or potassium acetate.
21. A process for the production of vinyl acetate which comprises
reacting ethylene with an oxygen-containing gas and optionally
water in the presence of a catalyst as claimed in any one of claims
1 to 20.
22. A process as claimed in claim 21 carried out at a temperature
of from 100 to 400.degree. C. and under a pressure of 1 to 20 barg.
Description
[0001] The present invention relates to a process for the
production of vinyl acetate and to a novel catalyst for use in the
process.
[0002] Vinyl acetate is generally prepared commercially by
contacting acetic acid and ethylene with molecular oxygen in the
presence of a catalyst active for the production of vinyl
acetate.
[0003] The catalyst suitable for use in the production of vinyl
acetate may comprise a Group VIII metal, for example palladium, an
alkali metal acetate promoter, for example sodium or potassium
acetate, and an optional co-promoter, for example cadmium acetate
or gold. In particular U.S. Pat. No. 5,185,308 discloses a process
for preparing vinyl acetate by the catalytic oxidation of ethylene
in the presence of acetic acid. The catalyst used is a supported
palladium catalyst promoted with gold and potassium acetate.
[0004] Acetic acid, useful as a feedstock for the production of
vinyl acetate, may be prepared by several methods as commonly
practiced in the industry, for example by the liquid phase
carbonylation of methanol and/or a reactive derivative thereof in
the presence of a Group VIII noble metal catalyst, an alkyl iodide
promoter and a finite concentration of water. The acetic acid
produced is then used as a reactant in the production of vinyl
acetate. The process, thus tends to be a two stage process.
[0005] U.S. Pat. No. 3,373,189 relates to a process for the
production of vinyl acetate from ethylene and oxygen using a
palladium catalyst. U.S. Pat. No. 4,188,490 discloses a process for
the production of acetic acid and vinyl acetate using a palladium
catalyst on a zinc oxide support. U.S. Pat. No. 3,637,818 discloses
a process for the production of acetaldehyde, acetic acid and vinyl
acetate by the oxidation of ethylene in the presence of a noble
metal and manganese or cobalt oxides. The aforementioned processes
are carried out in the liquid phase.
[0006] We have now found that vinyl acetate can be produced
directly from a reactant mixture comprising ethylene, optionally
water, and an oxygen-containing gas without the need to initially
produce acetic acid as a separate stage in the overall process
Through the use of a modified palladium catalyst, vinyl acetate can
be produced directly in a one stage process.
[0007] Accordingly, the present invention provides a process for
the production of vinyl acetate which comprises reacting ethylene
with an oxygen-containing gas, and optionally water, in the
presence of a catalyst comprising (1) a catalyst support, (2)
palladium, (3) an acid, (4) at least one acetic acid catalyst
promoter and (5) at least one vinyl acetate catalyst promoter
and/or co-promoter.
[0008] In a further embodiment of the present invention there is
provided a catalyst for use in the production of vinyl acetate
which comprises (1) a catalyst support, (2) palladium, (3) an acid,
(4) at least one acetic acid catalyst promoter and (5) at least one
vinyl acetate catalyst promoter and/or co-promoter.
[0009] The present invention provides a novel and cost effective
route for the production of vinyl acetate. The process is not only
highly selective towards the production of vinyl acetate but does
not require the independent and separate production of acetic acid
which is then used as a co-reactant in the process. In contrast,
use of the modified palladium catalyst results in the in-situ
oxidation of the reactants to produce acetic acid which is then
oxidised with ethylene to vinyl acetate. The bi-functional nature
of the catalyst results in a direct process.
[0010] The present invention provides a process for the production
of vinyl acetate from ethylene, an oxygen-containing gas and
optionally water. The ethylene may be substantially pure or may be
admixed with one or more of nitrogen, methane, ethane, carbon
dioxide, hydrogen, and low levels of C.sub.3/C.sub.4 alkenes or
alkanes.
[0011] The oxygen-containing gas may be air or a gas richer or
poorer in molecular oxygen than air. Suitably, the gas may be
oxygen diluted with a suitable diluent, for example nitrogen or
carbon dioxide. Preferably, the oxygen-containing gas is
oxygen.
[0012] Water may be optionally co-fed into the reaction chamber.
Where water is present in the reaction chamber, it may be present
in an amount up to 50 volume percent, preferably in the range from
10 to 30 volume percent.
[0013] A small amount of acetic acid may also be introduced into
the reaction chamber. Suitably, the acetic acid may be introduced
through a recycle stream. Where it is desired to introduce acetic
acid, this may be present in an amount up to 50 volume percent,
preferably in the range from 5 to 20 volume percent.
[0014] The catalyst of the present invention comprises palladium.
The palladium concentration may be greater than 0.5% by weight,
preferably greater than 1% by weight based upon the total weight of
the catalyst. The palladium concentration may be as high as 10% by
weight for fixed bed or fluid bed applications.
[0015] The catalyst of the present invention is a supported
catalyst. Suitable catalyst supports may comprise porous silica,
alumina, silica/alumina, titania, zirconia or carbon. Preferably,
the support is silica. Suitably, the support may have a pore volume
from 0.2 to 3.5 ml per gram of support, a surface area of 5 to 800
m.sup.2 per gram of support and an apparent bulk density of 0.3 to
1.5 g/ml. For catalysts used in fixed bed processes, the support
typically has dimensions of 3 to 9 mm and may be spheric, tablet,
extrudate, pill shaped or any suitable shape. For catalysts used in
fluid bed processes, the support typically may have a particle size
distribution such that at least 60% of the catalyst particles have
a particle diameter of below 200 microns, preferably at least 50%
less than 105 microns and no more than 40% of the catalyst
particles have a diameter of less than 40 microns.
[0016] The catalyst composition comprises at least one acetic acid
catalyst promoter. Suitable promoters include selenium, titanium,
tellurium and/or vanadium-containing compounds. Preferably, the
acetic acid catalyst promoter is an oxide, acetate or
acetylacetonate of at least one of the aforementioned metals.
Preferably, the acetic acid catalyst promoter content of the final
catalyst is up to 10% by weight.
[0017] In addition to the palladium compound and the acetic acid
promoter, the catalyst comprises at least one vinyl acetate
catalyst promoter and/or co-promoter, preferably both a promoter
and a co-promoter. Suitable promoters include gold, copper and/or
nickel, and cadmium acetate. A preferred promoter is gold. Suitable
sources of gold include gold chloride, tetrachloroauric acid
HAuCl.sub.4, NaAuCl.sub.4, KAuCl.sub.4, dimethyl gold acetate,
barium acetoaurate or gold acetate. The preferred gold compound is
HAuCl.sub.4. The metal may be present in an amount of from 0.1 to
10% by weight in the finished catalyst. Suitable co-promoters
include alkali or alkaline earth metal salts, preferably an acetate
salt, such as potassium or sodium acetate. Preferably, the
co-promoter content in the final catalyst is in the range from 0.1
to 9.5% by weight as acetate. A preferred catalyst component (5) is
gold and either sodium or potassium acetate.
[0018] The catalyst composition comprises an acid. Preferably, the
acid is a strong acid. Suitable acids comprise heteropolyacids
which may include silicotungstic acid, phosphotungstic acid,
phosphomolybdic acid, silicomolybdic acid, tungstomolybdophosphoric
acid, tungstomolybdosilisic acid, tungstovanadophosphoric acid,
tungstovanadosilisic acid, molybdovanadophosphoric acid,
molybdovanadosilisic acid, borotungstic acid, boromolybdic acid,
tungstomolybdoboric acid, molybdoaluminic acid, tungstoaluminic
acid, molybdotungstoaluminic acid, molybdogermanic acid,
tungstogermanic acid, molybdotungstogermanic acid, molybdotitanic
acid, tungstotitanic acid, molybdotungstotitanic acid,
cericmolybdic acid, cerictungstic acid, cericmolybdotungstic acid,
molybdocobalt acid, tungstocobalt acid, molybdotungstocobalt acid,
phosphoniobic acid, siliconiobic acid and silicotantalic acid.
Among them, silicotungstic acid, phosphotungstic acid,
phosphomolybdic acid, silicomolybdic acid, tungstomolybdophosphoric
acid, tungstomolybdosilisic acid, tungstovanadophosphoric acid,
tungstovanadosilisic acid, molybdovanadosilisic acid, borotungstic
acid, boromolybdic acid and boromolybdotungstic acid are especially
preferred. Preferably, the acid content in the final catalyst is up
to 50% by weight.
[0019] The final catalyst composition may suitably be optimised to
maximise vinyl acetate production rate whilst maximising
selectivity.
[0020] The catalyst of the present invention may suitably be
prepared by the method described in detail in GB-A-1559540. In the
first stage of the preparation process, the support is impregnated
with a solution containing the required palladium and the promoter
metal, for example gold, in the form of soluble salts. Example of
such salts include the soluble halide derivatives. The impregnating
solution is preferably an aqueous solution and the volume of
solution used is such that it corresponds to between 50 and 100% of
the pore volume of the support, preferably 95 to 99% of the pore
volume for fixed bed catalysts or 50 to 99% of the pore volume for
fluid bed catalysts.
[0021] After impregnation, the wet support is, optionally, treated
with an aqueous solution of an alkali metal salt selected from
alkali metal silicates, carbonates or hydroxides to develop a metal
shell structure familiar to those skilled in the art. The amount of
alkali metal salt used is such that after the solution has been in
contact with the impregnated support for between 12 and 24 hours,
the pH of the solution is suitably in the range 6.5 to 9.5,
preferably 7.5 to 8 when measured at 25.degree. C. The preferred
metal salts are sodium metal silicate, sodium carbonate and sodium
hydroxide.
[0022] During the treatment described above, palladium and
promoter, for example gold, hydroxides are believed to be
precipitated or incorporated onto the support. Alternatively, the
impregnated support can be dried at ambient or reduced pressure and
from ambient temperature to 150.degree. C., preferably 60 to
120.degree. C., prior to metals reduction. To convert such
materials into the metallic state, the impregnated support is
treated with a reducing agent such as ethylene, hydrazine,
formaldehyde or hydrogen. If hydrogen is used, it will usually be
necessary to heat the catalyst to 100 to 300.degree. C. in order to
effect complete reduction.
[0023] After the steps described above have been carried out, the
reduced catalyst is washed with water and then dried. The dried
carrier is then impregnated with the required amount of vinyl
acetate catalyst co-promoter, for example aqueous alkali metal
acetate, and acetic acid catalyst promoter, for example aqueous
selenium-containing compound, and thereafter dried. The dried
carrier is further treated with an appropriate amount of heteropoly
acid dissolved in water, and the final product dried.
[0024] The method of catalyst preparation may be varied to optimise
catalyst performance based on maximising vinyl acetate yield and
selectivity.
[0025] Preparation of vinyl acetate using the catalyst of the
present invention is typically carried out by contacting ethylene,
water and an oxygen-containing gas such as oxygen or air with the
catalyst at a temperature of from 100 to 400.degree. C., preferably
140 to 210.degree. C. and a pressure of 1 bar to 20 barg,
preferably 6 to 15 barg.
[0026] The process may be carried out in a fixed bed or a fluidised
bed reactor and is preferably carried out in the gas phase.
[0027] The present invention will now be illustrated with reference
to the following Examples.
[0028] Example 1 is an example according to the present invention.
Comparative Examples A, B and C are not according to the invention
wherein the process utilised a catalyst not according to the
present invention, Example A because it does not contain a vinyl
acetate catalyst promoter or co-promoter, Example B because it does
not contain an acid or an acetic acid catalyst promoter, and
Example C because the acetic acid catalyst component and the vinyl
acetate catalyst component are in separate beds.
EXAMPLE 1
[0029] (a) Preparation of the Catalyst.
[0030]
[0031] In an aqueous solution containing 1.7 g of sodium
tetrachloropalladate (II) and 1.5 g of sodium tetrachloroaurate
(III) hydrate dissolved in 34 g of water was placed 68.4 g of a
porous silica carrie (KA 160 ex Sud Chemie) having a particle size
5 mm to 7 mm to absorb the entire solution. The resultant carrier
was added to 76.5 g of an aqueous solution containing 6.5 g of
sodium metasilicate and covered completely by the solution. The
mixture was allowed to stand for 18 hours and then 20 g of 99%
hydrazine hydrate was added to the solution to reduce Pd and Au.
The resultant mixture was allowed to stand for 4 hours or until the
reduction was complete. The carrier was separated from solution and
washed with deionised water until no chloride ion was found in the
effluent using a AgNO.sub.3 solution. The resultant carrier was
dried at 60.degree. C. for 24 hours. In an aqueous solution
containing 0.0071 g of potassium selenate (VI) and 0.51 g of
potassium acetate dissolved in 5 g of water was added 10 g of the
dried carrier. The carrier absorbed the entire solution and was
dried at 60.degree. C. for 24 hours. Thereafter, an aqueous
solution containing 3.3 g of silicotungstic acid hydrate dissolved
in 5 g water was added to the carrier and absorbed entirely. The
resultant carrier containing Pd, Au, selenium salt and
silicotungstic acid was dried at 60.degree. C. for 24 hours.
[0032] Production of Vinyl Acetate
[0033] 5 g of the resultant catalyst was distributed evenly in 60
mls glass beads (size 1 mm) in a reaction tube. A mixture of
ethylene, oxygen, steam and inert gas in a volume ratio of
40:6:31:23 was introduced into the unit at a temperature of
160.degree. C. and a pressure of 8 barg at a flow rate of 15.8
NL/hr to effect reaction. The effluent was analysed on line by gas
chromatography. Vinyl acetate space time yield of 84.5 g/hr.L and
selectivity of 76% was obtained based on carbon balance. CO.sub.2
selectivity was 22%.
COMPARATIVE EXAMPLE A
[0034] Preparation of Catalyst
[0035] Sodium tetrachloropalladate (II)(9.5 g) was dissolved in
water (90 g). A porous silica carrier (KA 60 ex Sudchemie, particle
size 5 mm to 7 mm) (180 g) was impregnated with this aqueous
solution until the entire solution was absorbed. The resultant
carrier was added to an aqueous solution (170 g) containing sodium
metasilicate (17.7 g). The mixture as allowed to stand for 18 hours
and then 20 g of 99% hydrazine hydrate was added to the solution to
reduce the palladium. The resultant mixture was allowed to stand
for 4 hours or until the reduction was complete. The carrier was
separated from the solution and washed with de-ionised water until
no chloride ion was found in the effluent using a AgNO3 solution.
The resultant carrier was dried at 60.degree. C. for 48 hours.
Potassium selenate (VI) (0.164 g) was dissolved in water (10 g) and
was absorbed entirely by 20 g of the dried carrier. Then the
carrier was dried again at 60.degree. C. for 24 hours. Thereafter,
an aqueous solution containing silicotungstic acid hydrate (6.3) g
dissolved in water (10 g) was added to the carrier and absorbed
entirely. The resultant carrier containing palladium, selenium salt
and silicotungstic acid was dried at 60.degree. C. for 24
hours.
[0036] Five gram of the resultant catalyst was distributed evenly
in 60 nls of glass beads (size 1 mm) in a reaction tube, a mixture
of ethylene, oxygen, steam and an inert gas in a volume ratio of
40:6:31:23 was introduced into the unit at a temperature of
150.degree. C. and a pressure of 8 bar G at a flow rate of 15.5
Nl/hr to effect reaction. The effluent was analysed on line by gas
chromatography.
[0037] As a result the following data was obtained: acetic acid
space time yield of 235 g/hr. 1, vinyl acetate space time yield of
2.1 g/hr. 1, acetaldehyde space time yield of 3.5 g/hr. 1 and
carbon dioxide space time yield of 21.2 g/hr. 1. Overall
selectivity to acetic acid was 87% and overall selectivity to vinyl
acetate was 0.54%.
COMPARATIVE EXAMPLE B
[0038] (a) Preparation of Catalyst
[0039] Vinyl acetate catalyst prepared according to U.S. Pat. No.
5,185,308 with nominal loadings of 0.9 Pd, 0.4 Au and 7 wt % KOAc
on KA 60.
[0040] Two and half gram of the resultant catalyst was distributed
evenly in 60 mls of glass beads (size 1 mm) in a reaction tube, a
mixture of ethylene, oxygen, steam and an inert gas in a volume
ratio of 47:7:19:27 was introduced into the unit at a temperature
of 150.degree. C. and a pressure of 8 bar G at a flow rate of 21.1
Nl/hr to effect reaction. The effluent was analysed on line by gas
chromatography.
[0041] As a result the following data was obtained carbon dioxide
space time yield of 119.6 g/hr. 1, no acetic acid, vinyl acetate or
other by-products were detected.
COMPARATIVE EXAMPLE C
[0042] (a) Preparation of Catalyst
[0043] Catalysts were prepared according to Comparative Examples A
and B.
[0044] (b) Production of Vinyl Acetate
[0045] A reaction tube was packed with Catalyst 1 (5 g) and 2 (2.5
g) and glass beads (60 ml, size 1 mm). Catalyst 1 distributed
evenly in glass beads (32 ml) was placed in the upper part of the
tube and Catalyst 2 in glass beads (16 ml) at the lower. There were
2 ml glass beads between Catalyst 1 section and Catalyst 2, and 5
ml each at the top and the bottom of the tube. A mixture of
ethylene, oxygen, steam and an inert gas in a volume ratio of
50:8:21:21 was introduced into the unit at a temperature of
150.degree. C. and a pressure of 8 bar G at a flow rate of 15.8
Nl/hr to effect reaction. The effluent was analysed by on line gas
chromatography.
[0046] The following results were obtained: vinyl acetate space
time yield of 115 g/hr. 1 with a selectivity of 77% based on carbon
balance, CO2 selectivity of 11% and acetic acid selectivity of 5%.
Ethyl acetate and ethanol were minor byproducts.
[0047] It can be seen that reaction selectivities are only achieved
which are comparable to those achieved from the claimed process
when a two-stage process is operated.
* * * * *