GB910484A - Production of carboxylic acids - Google Patents

Abstract

Liquid catalyst compositions comprising the combination product of a heavy metal oxidation catalyst, in which the metal is in the form of a salt, metallate, oxide, hydroxide or hydrated from thereof, and aqueous hydrobromic acid are described. They are used in the liquid phase oxidation of organic compounds to carboxylic acids (see Group IV(b)). The metal is preferably vanadium, chromium, manganese, iron, cobalt or nickel but molybdenum, palladium, tungsten, neodymium, cerium, copper, nitheniam, osmium and rhodium are also mentioned. In examples: (1) catalysts are prepared by mixing 48% aqueous hydrobromic acid and nickel acetate, chromic acetate, ferrous bromide or cerium oxide; (2) neodymium ammonium nitrate and aqueous hydrobromic acid are reacted together generating bromine, most of which remains in the solution obtained as product.ALSO:An aromatic or heterocyclic organic compound having one or more aliphatic nuclear substitutents is oxidised to form a carboxylic acid by treatment in liquid phase with molecular oxygen in the presence of a liquid catalyst composition comprising the combination product of a heavy metal oxidation catalyst, in which the metal is in the form of a salt, metallate, oxide, hydroxide or hydrated form thereof, and aqueous hydrobromic acid. In general such a catalyst composition is soluble in the reaction mixture under the conditions of oxidation. The molar ratio of hydrobromic acid to heavy metal may be in the range of 1/5 to 5/1. The heavy metal is preferably vanadium, chromium, manganese, iron, cobalt, or nickel. Other metals mentioned are molybdenum, palladium, tungsten, neodymium, cerium, copper, ruthenium, osmium, and rhodium. Chlorides, chlorates, bromides, acetates, benzoates, nitrates, and other salts of the metals may be used, as well as metallates such as chromates and molybdates. Oxygen, ozone, or air may be used and the oxidation may take place at 60 DEG -275 DEG C. The reaction may be carried out in the presence of an inert liquid reaction medium such as acetic acid. Examples describe the production of terephthalic acid from p-xylene using as catalyst a liquid preparation formed by mixing nickel acetate chromic acetate, ferrous bromide, cerium oxide, or neodymium ammonium nitrate with a 48% aqueous hydrobromic acid solution. The application of the process to the oxidation of other starting materials and the production of other carboxylic acids is referred to e.g. the oxidation of toluene, durene, mesitylene, diisopropyl benzenes, and p-cymene to the corresponding mono or poly-carboxylic acids; acenaphthene to naphthalic acid; methyl naphthalene to naphthoic acid; ditolyl ethane to iso- and tere-phthalic acids; acetophenone to benzoic acid; p-toluene sulphonic acid to p-sulphobenzoic acid; p-nitrotoluene to p-nitrobenzoic acid; chloro-p-xylene to chloroterephthalic acid; hydroxy-methyl-pyridines and picolines to nicotinic and isonicotinic acids.