GB840822A - Improvements in and relating to the production of benzoic acid and substituted derivatives thereof - Google Patents

Abstract

The invention comprises a process for the preparation of aromatic carboxylic acids by the oxidation in the liquid phase by means of ozone or molecular oxygen, of alkyl aromatic compounds or their closely related oxygenated derivatives at elevated temperature and pressure, using a catalyst comprising a metal of variable valence, in which the proportion of bromine is less than 7.8 X 10-5 but not less than 1 X 10-7 gram atom per gram mol. of starting material. The molecular oxygen may be introduced as such or as air or diluted air. Suitable temperatures are 100-300 DEG C., and pressures up to 50 atmospheres may be used. The process may be carried out in chromium/nickel austenitic or mild steel reactors. Bromine may be introduced as such or as bromide e.g. hydrogen bromide, or a metallic or organic bromide. Metals specified are cobalt, manganese or mixtures thereof, cerium and lead. The concentration of metal may be e.g. 1-0.0005 gram atom per mol. of starting material. The metal may be introduced e.g. as the acetate, nonanoate, propionate or naphthenate, and a solvent e.g. acetic acid, propionic acid or orthodichlorobenzene may be present in the reaction mixture. Starting materials mentioned are monoalkyl benzenes, and their aldehydes, alcohols, esters and hydroperoxide, e.g. toluene ethylbenzene, cumene, n and secbutyl benzene, but not those in which the alkyl group is tertiary. Substituents which may be present in the starting materials are NO2, SO2 and SO2NH2. An example is given of the oxidation of toluene to benzoic acid using various concentrations of cobalt, and bromine in the reaction mixture. Specifications 804,612 and 810,020 are referred to.