Patent ID: 7799945

Claim:
A catalytic process for preparing aliphatic straight-chain and β-alkyl-branched carboxylic acids of 5 to 13 carbon atoms comprising oxidizing the corresponding aldehydes with oxygen or oxygen-containing gas mixtures at 20 to 100° C. in the liquid phase, wherein the oxidation of the aldehyde is carried out in the presence of a catalyst system which is the reaction product from a separate aldehyde oxidation reaction in which the aldehyde oxidation reaction in which the aldehyde oxidation reaction is carried out in the presence of alkali metal carboxylates or alkaline earth metal carboxylates or a mixture thereof in an amount, calculated as alkali or alkaline earth metal, of 0.5 mmol to 5 mmol per mol of aldehyde used and of 0.05 to 5.0 ppm of a metal of groups 4 to 12 of the Periodic Table, cerium or lanthanum or the corresponding amount of a compound of such a metal or a mixture of such metals and metal compounds, based on the aldehyde used, and after said separate aldehyde oxidation reaction, the carboxylic acids formed, unreacted starting aldehyde and further volatile constituents are distilled off from the reaction mixture and the distillation residue containing the reaction product is used for the subsequent, actual aldehyde oxidation reaction.