DE2436177

A process for producing an aromatic carboxylic acid by liquid-phase oxidizing an alkylbenzene with a molecular oxygen-containing gas in a lower aliphatic carboxylic acid solvent in the presence of a heavy-metal-bromine oxidation catalyst, in which the oxidation reaction is conducted using a material containing as inorganic elements only cobalt, manganese, and bromine as the catalyst components and while withdrawing from the reaction system, at least partially, the condensed liquid of a gaseous mixture discharged from the top of the reactor during the reaction and maintaining the water content of the reaction system below a definite level by introducing fresh solvent (or, preferably, the solvent recovered as a side cut fraction by distilling the condensed liquid) in an amount corresponding to the amount of the solvent withdrawn contained in the condensed liquid, and a reaction mother liquor which is formed by separating the aromatic carboxylic acid from the reaction mixture withdrawn from the reactor is recycled, as it is, to the reactor for reuse in the oxidation reaction.