PROCESS FOR PREPARING AROMATIC CARBOXYLIC ACIDS

摘要

The invention relates to a process for preparing aromatic carboxylic acids by oxidation of an alkyl-aromatic hydrocarbon in the liquid phase in the absence of an aliphatic carboxylic acid, by means of a gas containing molecular oxygen and in the presence of a catalyst consisting of a cobalt compound that is soluble in the reaction mixture. The process according to the invention is characterized by the fact that in addition to the cobalt compound a catalyst is used that consists of a zirconium and/or hafnium compound soluble in the reaction mixture. The use of zirconium and/or hafnium as a catalyst in addition to cobalt enables a higher reaction rate to be reached at the same temperature, or the reaction to be carried out at a lower temperature with the same reaction rate, with a considerably better selectivity for the desired aromatic carboxylic acid being obtained at the same reaction rate than if only cobalt is used under otherwise identical conditions.