GB810020A - Process for the preparation of aromatic mono carboxylic acids - Google Patents

Abstract

Aromatic monocarboxylic acids are prepared by reacting in liquid phase an aromatic compound having an aliphatic nuclear substituent oxidizable to a carboxy group, with molecular oxygen in the presence of a catalyst comprising in conjoint presence bromine and a heavy metal oxidation catalyst. Specified heavy metals are manganese, cobalt, iron and nickel. The metal and bromine may be added in ionic form, for example as the metal bromide or as separate salts, one containing the metal and the other bromine. Alternatively the metal may be present as a carboxylate and the bromine added as a non-metallic or organic bromide. The oxidation process is preferably carried out in the presence of an inert organic medium, preferably a saturated aliphatic monocarboxylic acid containing 2 to 8 carbon atoms, or benzoic acid. Pure oxygen or a mixture of oxygen and inet gases, such as air, may be used. The process may be carried out batchwise or continuously and partially oxidized material may be separated from the product and recycled. Water may be removed from the reaction mixture, for example by distillation or by adding acetic anhydride. Sufficient pressure is applied to the reaction system to maintain a liquid phase. Specified starting materials are methyl-, ethyl-, isopropyl-, n-butyl- and sec.-butyl-benzenes, tert.-butyl-toluenes, a - or b -methyl-naphthalenes, acetophenone, benzaldehyde, a -tolualdehyde, benzyl or phenethyl alcohols, acetonaphthones, naphthyl-methanols or ethanols, and a -naphthaldehyde. In examples a mixture of ethylbenzene, acetic acid and manganese bromide is treated with air at a temperature of 196 DEG C. and 400 pounds per square inch pressure to give benzoic acid; p-tert. butyl-toluene treated similarly gives p-tert. butyl-benzoic acid.