GB942415A - Preparation of adipic and alkyladipic acids - Google Patents

Abstract

Adipic or alkyladipic acids are made by oxidising with a molecular oxygen containing gas hexahydrobenzoic acid or an alkyl substituted hexayhdrobenzoic acid at 50-150 DEG C. in the liquid phase in the presence of a catalyst soluble in the reaction mixture which provides as the catalytically active constituent a simple cation of chromium, manganese, iron, cobalt, nickel or copper. The catalyst may be added to the reaction mixture in the form of finely divided metal, as the metal oxide, hydroxide, carbonate or carboxylate. The preferred catalyst is cobalt, at 80 to 120 DEG C. The oxidation mixture may contain as solvent an aliphatic or aromatic carboxylic acid, or their methyl or ethyl esters, especially acetic acid. Cyclohexanol and/or cyclohexanone are formed as by-products and can be recovered as such or re-circulated with the starting materials. Cyclohexyl acetate and the lower dicarboxylic acids may also be obtained as by-products. The reaction may be effected at atmospheric or supertmospheric pressure. Toluene or xylene may be used as the primary starting material for conversion to hexahydrobenzoic acids by side chain oxidation followed by catalytic ring reduction. Examples describe batchwise and continuous operation of the process and give details of the separation of the reaction products and methods of assay.