Bp Chemicals Limited

David J Gulliver

Robert G Beevor

Simon James Kitchen

Robert M Sorrell

Neil A Greener

In a process for the preparation of palladium and palladium/gold shell type catalysts for vinyl acetate production, the improvement comprises using a barium salt to precipitate water-insoluble palladium and optional gold compounds onto a support prior to reduction with a reducing agent. A barium salt additive may also be introduced to the catalyst after reduction to reduce the tendency of the catalyst to deactivate with use.

Process for the preparation of vinyl acetate

A process for preparing a carboxylic acid having (n+1) carbon atoms (e.g. acetic acid) from an alcohol having n carbon atoms (e.g. methanol) by liquid phase, rhodium catalyses carbonylation is provided. The process is characterized by using a catalyst stabilizer selected from certain classes of imidazolium iodides, alkyl substituted pyridinium iodides and hydroxypyridinium iodides. Most preferred are those derived from the amines 2-ethyl-4-methyl imidazole, 4-ethylpyridine, 4-t-butylpyridine and 3,4-lutidine by quarternisation with a methyl group.

Preparing carboxylic acids

The solubility and stability of rhodium catalysts in rhodium-catalysed carbonylation of alkyl esters or alkyl ethers under substantially anhydrous conditions to produce carboxylic acid anhydrides is improved by the use of co-promoters selected from the group:

Process for the production of carboxylic acid anhydrides

A process for recovering Group VIII noble metals from tar is provided. The process involves heating a mixture of the Group VIII noble metal, tar and methyl iodide in a closed system at a temperature in excess of 50.degree. C. During the process the Group VIII noble metal is precipitated in an insoluble form which can be separated by e.g. filtration. Precipitation preferably takes place at a temperature in the range 120.degree. to 180.degree. C. The process is particularly suitable for the recovery of either rhodium or iridium.

Recovery of noble metals

A process for recovering Group VIII metals from process streams derived from carbonylation processes is provided. The process comprises contacting the process stream with an extracting stream comprising acetic acid in water and thereafter recovering the extracting stream. The process stream is preferably one which contains tar and is produced by diluting a side stream from a carbonylation reactor with methyl iodide. During the process the Group VIII metal is extracted into the extracting stream from the process stream.

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North Humberside, United Kingdom

David J Gulliver