Preparation of phthalic acid by solventless oxidation of liquid ortho-xylene

摘要

This invention relates to the preparation of o-phthalic acid by the oxidation of liquid o-xylene with a source of molecular oxygen at a temperature in the range of from 150 DEG C. up to 235 DEG C. in the presence of catalysis provided by the combination of components which include a source of bromine and at least cobalt as metal oxidation catalyst, in the presence of liquid water in an amount to activate said catalysis and solubilize a catalytically effective amount of metal oxidation catalyst in liquid phthalic acid and under conditions which retain substantially all the o-phthalic acid in the free acid form but in the absence of any material extraneous to the oxidation reaction or its products as solvent. Such preparative process results in yields of 85 to 92 mole percent and higher to o-phthalic acid in but a single oxidation step with recycle thereto of only o-xylene vaporized from the reaction zone and recovered.