GB2129430A

GB2129430A - Preparing ethyl acetate and ethylidene diacetate

Info

Publication number: GB2129430A
Application number: GB08328140A
Authority: GB
Inventors: Alexander George Kent
Original assignee: BP Chemicals Ltd
Current assignee: BP Chemicals Ltd
Priority date: 1982-10-27
Filing date: 1983-10-21
Publication date: 1984-05-16
Also published as: GB8328140D0

Abstract

Ethyl acetate or ethylidene diacetate is prepared by reacting acetic anhydride with hydrogen in the presence of carbon monoxide and, as catalyst, an effective amount of a Group VIII noble metal e.g. Ru compound that is substantially free of biphyllic ligands containing phosphorus, arsenic or antimony. The amount of carbon monoxide should be at least 5% of the total volume of hydrogen and carbon monoxide and the reaction selectivity can be controlled towards ethyl acetate or ethylidene diacetate, by variation in time and reaction temperature.

Description

SPECIFICATION Process for the preparation of esters This invention relates to a process for the production of esters, more particularly to the production of esters such as ethylidene diacetate or ethyl acetate.

Ethylidene diacetate is a chemical intermediate having a number of uses. It can, for example, be converted into vinyl acetate and acetic acid (Kirk Othmer "Encyclopaedia of Chemical Technology" 2nd Edition, Volume 21, page 321, Interscience New York 1980).

The preparation of ethylidene diacetate has been previously described in US Patent No.

3,579,566 which discloses the reaction of acetic anhydride with hydrogen in the presence of carbon monoxide and a catalyst comprising a Group VIII noble metal complex with a biphyllic ligand of phosphorus, arsenic or antimony and in GB Patent Application No. 2,075,508A which describes a process for the preparation of ethylidene diacetate from acetic anhydride by reacting the acetic anhydride with hydrogen in the presence of a catalyst comprising palladium, ruthenium or rhodium and in the substantial absence of carbon monoxide.

It has now been found however that the above described reaction can be significantly improved (i) using a Group VIII noble metal catalyst free of biphyllic ligands and by including carbon monoxide in the reaction mixture. The incorporation of the carbon monoxide into the reaction mixture makes it possible to produce both or either ethylidene diacetate and ethyl acetate and also to control the relative amounts of the two by adjustment of the reaction conditions.

Thus, according to the present invention a process for the production of ethyl acetate or ethylidene diacetate comprises reacting acetic anhydride with hydrogen in the presence of carbon monoxide and as catalyst, an effective amount of a group Vll noble metal compound that is substantially free of biphyllic ligands containing phosphorus, arsenic or antimony.

The term Group VIII noble metal means ruthenium, rhodium, palladium, osmium, iridium and platinum.

Preferably the Group Vlil noble metal compound is a ruthenium compound conveniently in a form that is soluble in the reaction mixture under the reaction conditions such as a soluble salt e.g. a halide or carbonyl.

Typically the catalyst is employed in an amount of 5 to 10,000 ppm weight of metal for weight of acetic an hydride, preferably 100 to 5000 ppm.

Preferably the process is operated under conditions which maintain the acetic anhydride, ethyl acetate and ethylidene diacetate in the liquid phase, for example at pressures in the range 50 to 150 bar.

Preferably the process is operated at an elevated temperature for example up to 2400 C, preferably in the range 50 to 1800 C.

By appropriate adjustment of the reaction conditions it is possible to produce either ethylidene or ethyl acetate and avoid problems associated with separation.

To increase the yield of ethyl acetate the reaction is preferably operated under conditions of higher temperature and longer reaction times, for example, at a temperature of over 1 500C and reaction time of greater than 6 hours. To increase the yield of ethylidene diacetate, lower temperature and shorter reaction times are preferred, for example, tempertures up to 1 500C and reaction times of 3 hours or less.

The amount of carbon monoxide should preferably be at least 5 vol % based on the total volume of hydrogen and carbon monoxide.

Convenient molar proportions of hydrogen to carbon monoxide are in the range 1:1 to 10:1.

The process can be conveniently effected using a reaction mixture which initially consists substantially of acetic anhydride, hydrogen, carbon monoxide and catalyst, for example the liquid phase may contain at least 95% by wt of acetic anhydride. The process can be effected by feeding the reactants comprising acetic anhydride, hydrogen, and carbon monoxide to a reaction zone.

The invention is illustrated by the following Examples.

In all the examples and the comparative experiments all the reactants and products (except the carbon monoxide and hydrogen) were in the liquid phase and in each case the catalyst was employed in solution.

Example 1 A 100 ml Hastelloy '82' autoclave was charged with 41.0 g of acetic anhydride and 0.200 g ruthenium trichloride. The reactor was purged with carbon monoxide, pressurized with carbon monoxide (partial pressure 200 psi) and hydrogen (partial pressure 1000 psi), then heated at 1 50 C during 3 hours with stirring. After cooling the reaction mixture, g.c. analysis showed it to contain 8.1 g of ethylidene diacetate, 7.0 g of acetic acid and 0.6 g of ethyl acetate, thus more than 50% of the liquid reaction product was ethylidene diacetate.

Example 2 A 100 ml Hastelloy 'B2' autoclave was charged with 41.0 g acetic an hydride and 0.203 g ruthenium carbonyl chloride. The autoclave was purged with carbon monoxide then pressurized with carbon monoxide (200 psi) and hydrogen (1000 psi). The temperature in the reaction vessel was brought to 1 500C and the reaction continued for three hours with stirring. After cooling, gas chromatography (g.c.) analysis of the reaction mixture showed it to contain 2.4 g of ethylidene diacetate and 5.5 g of acetic acid and no detectable amount of ethyl acetate.

Example 3 A 100 ml Hastelloy 'B2' autoclave was charged with 41.0 g of acetic anhydride and 0.253 g of ruthenium trichloride. The autoclave was purged with carbon monoxide and then pressurized with carbon monoxide (200 psi) and hydrogen (1000 psi). The temperature in the reaction vessel was raised to 1 5O0C and the reaction continued for eight hours with stirring. After cooling, g.c.

analysis of the reaction mixture showed it to contain 12.1 g of ethyl acetate and 30.1 g of acetic acid and no detectable amount of ethylidene diacetate.

This example illustrates that with the longer reaction time (eight hours compared with 3 hours in Examples 1 and 2) the main products are ethyl acetate and acetic acid.

Example 4 A 100 ml Hastelloy'B2' autoclave was charged with 41.0 g acetic anhydride and 0.200 g ruthenium trichloride and pressurised with carbon monoxide and hydrogen (relative partial pressures 200 and 1000 psi). The autoclave was then heated at 1 500C during 3 hours with stirring.

After cooling the reaction mixture g.c. analysis showed it to contain 8.1 g of ethylidene diacetate, 7.0 g of acetic acid and 0.6 g of ethyl acetate.

Comparative experiment A: Use of ruthenium catalyst in the absence of carbon monoxide A 100 ml Hastelloy 'B2' autoclave was charged with 41.0 g acetic anhydride and 0.102 g ruthenium trichloride and pressurised with hydrogen to 1000 psi. The autoclave was then heated at 150"C during 3 hours with stirring.

After cooling the reaction mixture, g.c. analysis showed it to contain 1.8 g ethylidene diacetate, 27.6 g acetic acid and 9.8 g ethyl acetate.

Comparative experiment B: Use of palladium chloride catalyst in the absence of carbon monoxide Experiment A was repeated except that 0.200 g palladium chloride was used in place of ruthenium trichloride. The products were 4.4 g ethylidene diacetate and 4.9 g acetic acid, with no detectable amount of ethyl acetate.

Example 5: Use of palladium chloride catalyst with hydrogen and carbon monoxide Example 4 was repeated with 0.208 g palladium chloride in place of ruthenium trichloride. Analysis of the reaction mixture showed it to contain only traces of ethylidene diacetate.

This example compared with Experiment B shows that the palladium catalyst is less effective in the presence of carbon monoxide.

Comparative experiment C: Use of ruthenium phosphine complex as catalyst A 100 ml Hastelloy '82' autoclave was charged with 41.0 g acetic anhydride, 0.203 g ruthenium trichloride and 0.8 g triphenylphosphine and pressurised with carbon monoxide and hydrogen (respective partial pressures 200 to 1000 psi).

The autoclave was then heated at 1 500C during 3 hours with stirring. After cooling the reaction mixture, g.c. analysis showed it to contain 0.2 g ethylidene diacetate and 2.0 g acetic acid.

This experiment when compared with Example 4 shows the advantage of using a catalyst that is free of biphyllic ligands in the form of triphenylphosphine.

Claims

1. A process for the production of ethyl acetate or ethylidene diacetate which comprises reacting acetic anhydride with hydrogen in the presence of carbon monoxide and, as catalyst, an effective amount of a Group VIII noble metal compound that is substantially free of biphyllic ligands containing phosphorus, arsenic or antimony.

2. A process as claimed in claim 1 wherein the Group Villi noble metal compound is a ruthenium compound.

3. A process as claimed in claim 1 or claim 2 wherein the amount of carbon monoxide is at least 5% of the total volume of hydrogen and carbon monoxide.

4. A process as claimed in any one of the previous claims wherein the reaction conditions are controlled to produce ethyl acetate and less than 10% by weight of ethylidene diacetate based on the weight of liquid reaction products.

5. A process as claimed in any one of claims 1 to 3 wherein the reaction conditions are controlled so as to produce more than 50% by weight of ethylidene diacetate based on the weight of the liquid reaction products.

6. A process for the production of ethyl acetate or ethylidene diacetate substantially as hereinbefore described with reference to any one of the Examples.

7. Ethyl acetate or ethylidene diacetate whenever produced by a process as claimed in any one of claims 1 to 6.