Patent ID: 7368597

Claim:
A process for the production of a carboxylic acid and/or the alcohol ester of a carboxylic acid, which process comprises carbonylating an alcohol and/or a reactive derivative of the alcohol which is selected from the group consisting of esters, halides, ethers and mixtures thereof, thereof with carbon monoxide in a liquid reaction composition in a carbonylation reactor, said liquid reaction composition comprising said alcohol and/or a reactive derivative thereof, a carbonylation catalyst and an alkyl halide co-catalyst and optionally a finite concentration of water, wherein said catalyst comprises at least one of rhodium or iridium which is coordinated with a polydentate ligand wherein said polydentate ligand has a bite angle of at least 145° or forms a rigid Rh or Ir metal-ligand complex and wherein said polydentate ligand comprises at least two coordinating groups which independently contain P, N, As or Sb as the coordinating atom of at least two of the co-ordinating groups and wherein in said process there is maintained hydrogen at a hydrogen:CO mole ratio of at least 1:100 and/or the carbon monoxide feed to the carbonylation reactor contains at least 1 mol % hydrogen.