Title of Invention

"A CATALYST FOR USE IN THE PRODUCTION OF VINYL ACETATE"

Abstract A catalyst for use in the production of vinyl acetate which comprises (1) a catalyst support selected from porous silica, alumina, silica/alumina, titania, zirconia and carbon, (2) palladium, (3) a heteropolyacid, (4) at least one acetic acid catalyst promoter is selected from selenium, titanium, tellurium and/or vanadium-containing compounds and (5) at least one vinyl acetate promoter selected from the group consisting of cadmium acetate, gold, copper and nickel.
Full Text The present invention relates to a catalyst for use in the production of vinyl acetate.
The present invention relates to a process for the production of vinyl acetate and to a novel catalyst for use in the process.
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
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 US 5185308 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.
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.
US 3373189 relates to a process for the production of vinyl acetate from ethylene and oxygen using a palladium catalyst. US 4188490 discloses a process for the production of acetic acid and vinyl acetate using a palladium catalyst on a zinc oxide support. US 3637818 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.
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.
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.
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.
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.
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 Ca/C4 alkenes or alkanes.
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.
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/
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.
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.
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 m2 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
9mm 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.
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.
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 HAuCU,
NaAuCU, KAuCU, dimethyl gold acetate, barium acetoaurate or gold acetate. The
preferred gold compound is HAuCU. 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.
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.
The final catalyst composition may suitably be optimised to maximise vinyl
acetate production rate whilst maximising selectivity.
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.
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°C. The preferred metal salts are sodium metal silicate, sodium carbonate and
sodium hydroxide.
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°C, preferably 60 to 120°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°C in order to effect complete reduction.
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.
The method of catalyst preparation may be varied to optimise catalyst
performance based on maximising vinyl acetate yield and selectivity.
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°C,
preferably 140 to 210°C and a pressure of 1 bar to 20 barg, preferably 6 to 15
barg.
The process may be carried out in a fixed bed or a fluidised bed reactor and
is preferably carried out in the gas phase.
The present invention will now be illustrated with reference to the
following Examples.
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
(a) Preparation of the Catalyst.
In an aqueous solution containing 1.7g of sodium tetrachloropalladate (II)
and 1.5g of sodium tetrachloroaurate (III) hydrate dissolved in 34g of water was
placed 68.4g of a porous silica carrie (KA 160 ex Sud Chemie) having a particle
size 5mm to 7mm to absorb the entire solution. The resultant carrier was added to
76.5g of an aqueous solution containing 6.5g of sodium metasilicate and covered
completely by the solution. The mixture was allowed to stand for 18 hours and
then 20g 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 AgNOj solution. The
resultant carrier was dried at 60°C for 24 hours. In an aqueous solution containing
0.0071g of potassium selenate (VI) and O.Slg of potassium acetate dissolved in 5g
of water was added lOg of the dried carrier. The carrier absorbed the entire
solution and was dried at 60°C for 24 hours. Thereafter, an aqueous solution
containing 3.3g of silicotungstic acid hydrate dissolved in 5g water was added to
the carrier and absorbed entirely. The resultant carrier containing Pd, Au, selenium
salt and silicotungstic acid was dried at 60°C for 24 hours.
Production of Vinyl Acetate
5g of the resultant catalyst was distributed evenly in 60mls glass beads (size
1mm) 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°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.
CO2 selectivity was 22%.
Comparative Example A
Preparation of Catalyst
Sodium tetrachloropalladate (II)(9.5g) was dissolved in water (90g). A
porous silica carrier (KA160 ex Sudchemie, particle size 5mm to 7mm) (180g) was
impregnated with this aqueous solution until the entire solution was absorbed. The
resultant carrier was added to an aqueous solution (170g) containing sodium
metasilicate (17.7g). The mixture as allowed to stand for 18 hours and then 20g 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 AgN03 solution. The
resultant carrier was dried at 60°C for 48 hours. Potassium selenate (VI)(0.164g)
was dissolved in water (lOg) and was absorbed entirely by 20g of the dried carrier.
Then the carrier was dried again at 60°C for 24 hours. Thereafter, an aqueous
solution containing silicotungstic acid hydrate (6.3)g dissolved in water (lOg) was
added to the carrier and absorbed entirely. The resultant carrier containing
palladium, selenium salt and silicotungstic acid was dried at 60°C for 24 hours.
Five gram of the resultant catalyst was distributed evenly in 60mls of glass
beads (size 1mm) 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°C and a pressure of 8 bar G at a flow rate of 15.5Nl/hr to
effect reaction. The effluent was analysed on line by gas chromatography.
As a result the following data was obtained: acetic acid space time yield of
235 g/hr.l, vinyl acetate space time yield of 2.1 g/hr.l, acetaldehyde space time
yield of 3.5 g/hr.l and carbon dioxide space time yield of 21.2 g/hr.l. Overall
selectivity to acetic acid was 87% and overall selectivity to vinyl acetate was
0.54%.
Comparative Example B
(a) Preparation of catalyst
Vinyl acetate catalyst prepared according to US 5185308 with nominal
loadings of 0.9 Pd, 0.4 Au and 7 wt% KOAc on KA160.
Two and half gram of the resultant catalyst was distributed evenly in 60 mis
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°C and a pressure of 8 bar G at a flow rate of 21.1Nl/hr to
effect reaction. The effluent was analysed on line by gas chromatography.
As a result the following data was obtained carbon dioxide space time yield
of 119.6 g/hr.l, no acetic acid, vinyl acetate or other by-products were detected.
Comparative Example C
(a) Preparation of catalyst
Catalysts were prepared according to Comparative Examples A and B.
(b) Production of Vinyl Acetate
A reaction tube was packed with Catalyst 1 (5g) and 2 (2.5g) and glass
beads (60ml, size 1mm). Catalyst 1 distributed evenly in glass beads (32ml) was
placed in the upper part of the tube and Catalyst 2 in glass beads (16ml) at the
lower. There were 2ml glass beads between Catalyst 1 section and Catalyst 2, and
5ml 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°C and a pressure of 8 bar G at a flow rate of 15.8Nl/hr to
effect reaction. The effluent was analysed by on line gas chromatography.
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.
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.







WE CLAIM:

1. A catalyst for use in the production of vinyl acetate which comprises (1) a catalyst support selected from porous silica, alumina, silica/alumina, titania, zirconia and carbon, (2) palladium, (3) a heteropolyacid, (4) at least one acetic acid catalyst promoter is selected from selenium, titanium, tellurium and/or vanadium-containing compounds and (5) at least one vinyl acetate promoter selected from the group consisting of cadmium acetate, gold, copper and nickel.
2. A catalyst as claimed in claim 1, in which the heteropolyacid content is up to 50% by weight.
3. A catalyst as claimed in claim 1, in which the acetic acid catalyst promoter is an oxide, acetate or acetylacetonate.
4. A catalyst as claimed in any one of the preceding claims in which the vinyl acetate catalyst promoter is gold.
5. A catalyst as claimed in any one of the preceding claims further comprising at least one vinyl acetate catalyst co-promoter.
6. A catalyst as claimed in claim 5, in which the vinyl acetate catalyst co-promoter is selected from alkali or alkaline earth metal salts.
7. A catalyst as claimed in claim 6, in which the vinyl acetate co-promoter is sodium acetate or potassium acetate.





Documents:

1877-DEL-2005-Abstract-(04-02-2009).pdf

1877-del-2005-abstract.pdf

1877-DEL-2005-Claims-(04-02-2009).pdf

1877-del-2005-claims.pdf

1877-DEL-2005-Correspondence-Others-(04-02-2009).pdf

1877-DEL-2005-Correspondence-Others-(16-09-2009).pdf

1877-DEL-2005-Correspondence-Others-(23-09-2009).pdf

1877-del-2005-correspondence-others.pdf

1877-DEL-2005-Description (Complete)-(04-02-2009).pdf

1877-del-2005-description (complete).pdf

1877-del-2005-form-1.pdf

1877-del-2005-form-18.pdf

1877-DEL-2005-Form-2-(04-02-2009).pdf

1877-del-2005-form-2.pdf

1877-DEL-2005-Form-3-(04-02-2009).pdf

1877-DEL-2005-Form-3-(23-09-2009).pdf

1877-del-2005-form-3.pdf

1877-del-2005-form-5.pdf

1877-DEL-2005-GPA-(04-02-2009).pdf

1877-del-2005-gpa.pdf

1877-DEL-2005-Petition-137-(04-02-2009).pdf

1877-DEL-2005-Petition-138-(04-02-2009).pdf


Patent Number 243198
Indian Patent Application Number 1877/DEL/2005
PG Journal Number 40/2010
Publication Date 01-Oct-2010
Grant Date 29-Sep-2010
Date of Filing 19-Jul-2005
Name of Patentee BP CHEMICALS LIMITED
Applicant Address BRITANNIC HOUSE, 1 FINSBURY CIRCUS, LONDON EC2M 7BA, ENGLAND.
Inventors:
# Inventor's Name Inventor's Address
1 SIMON JAMES KITCHEN HILLSIDE HOUSE, MAIN STREET, HILLAM, NORTH YORKSHIRE LS25 5HG, ENGLAND.
2 DAIYI QIN UNIT 3 FLOOR 3, 21 WANGJIA XIANG, CHENGDU 610064, REPUBLIC OF CHINA.
PCT International Classification Number C08
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 9810928.3 1998-05-22 U.K.