GB1088183A - Benzene polycarboxylic acids - Google Patents

Abstract

Benzene polycarboxylic acids are prepared continuously by liquid phase oxidation of polyalkylbenzene hydrocarbons by a process comprising continuously and simultaneously introducing into an oxidation zone a liquid phase of benzoic acid, a catalyst system consisting essentially of a heavy metal oxidation catalyst and bromine, the heavy metal having an at. wt. of 50 to 200, molecular oxygen and a polyalkyl benzene hydrocarbon in the ratio corresponding to from 1.0 to 1.1 stoichiometric mole ratio of oxygen required to oxidize all the alkyl groups of the polyalkyl benzene to carboxylic acid groups; the oxidation zone is maintained at a constant temperature in the range of 340 DEG to 525 DEG F. and a pressure in the range of 300 to 500 p.s.i.g., and the liquid phase reaction mixture is continuously withdrawn from the oxidation zone to provide a residence time of polyalkylbenzene in the oxidation zone of from 20 to 120 minutes. Specified benzene polycarboxylic acids which may be obtained are phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, trimesic acid and pyromellitic acid. Specified heavy metals for use as catalysts are manganese, cobalt, nickel, chromium, vanadium, molybdenum, tungsten, tin, cerium or mixtures thereof. The metals may be added per se or as one of their compounds. The bromine may be in elemental form or as one of its compounds such as NH4Br, tetrabromoethane, KBrO3, or C6H5CH2Br.