Process for manufacturing high-purity o-toluic acid

Abstract

A process for manufacturing high-purity o-toluic acid from a partial oxidation product of o-xylene is disclosed. o-Toluic acid is widely used as a raw material for agricultural chemicals, medicines, polymerization initiators, and the like. Depending on its use, 99% by weight or more purity is demanded for o-toluic acid. Hitherto, o-toluic acid having purity of higher than 99% by weight could not be obtained by fractionation, and purification by fractional crystallization was used. Fractional crystallization is, however, and expensive operation and not only gives a low yield of product but also results a large amount of waste water. The process disclosed herein gives an economical, commercial way to obtain high purity o-toluic acid. In summary, a process for the manufacture of high purity o-toluic acid which comprises: subjecting an oxidation product of o-xylene to distillation to remove therefrom low boiling point components such as unreacted o-xylene and benzoic acid, and high boiling point components, of which the major component is o-methylbenzyl o-toluate, thus obtaining crude o-toluic acid, treating said crude o-toluic acid with ammonia of an amount 1 to 1.2 mol equivalent of o-phthalic acid contained in said crude o-toluic acid, and subjecting the product thus treated to distillation is disclosed.