Patent ID: 7598415

Claim:
A process for preparation and isolation of p-toluic acid by a single step liquid phase oxidation reaction of p-xylene in water which comprises oxidizing p-xylene or a mixture of p-xylene and p-toluic acid with oxygen, air, or an oxygen/nitrogen mixture, at a pressure of 3-25 Kg/cm 2 with an exit flow rate of 60-80 ml/min, in the presence of a catalytically active bromine-free salt of a transition metal selected from the group consisting of Co, Mn, Ce and combinations thereof in the range 5-160 mmol per mole of p-xylene in water in the range of 40-85 weight % of water based on a total weight of reaction mixture, at a temperature ranging between 130-150° C., for a period of 5-10 hrs, cooling the reaction mixture, removing any un-reacted p-xylene by washing the reaction mixture with an organic solvent, and filtering the reaction mixture to obtain the p-toluic acid as a desired product in a major amount and terephthalic acid in a minor amount.