Abstract: A process is disclosed for preparation of purified terephthalic acid containing 200 ppmw or less of p-toluic acid. A filter cake of purified terephthalic acid is prepared by filtering, under a differential pressure of about or greater than 0.5 psi over the system pressure and a temperature within the range of from about 100.degree. C. to about 205.degree. C., an aqueous slurry of purified terephthalic acid containing a solution of p-toluic acid. The aqueous solution of p-toluic acid remaining in the filter cake of purified terephthalic acid is displaced from the filter cake by water under a pressure gradient over the system pressure at a temperature within the range of from about 100.degree. C. to about 205.degree. C. Pressure flash evaporation of water remaining in the filter cake occurs upon release of the system pressure to lower pressure with consequent lower temperature. The crystalline terephthalic acid product containing 200 ppmw or less p-toluic acid can be dried under atmospheric pressure.

Abstract: Substantial proportions of methyl acetate and unreacted polymethylbenzene are recovered from the waste gas produced during the oxidation of a polymethylbenzene to its corresponding polycarboxylic acid by passing the waste gas, after being cooled for removal of water vapor, through at least one bed of activated carbon and subsequently desorbing the methyl acetate and polymethylbenzene from the bed by passing a desorbing medium, such as steam, through the bed. Preferably, the cooled stream is heated to a temperature of at least 21.degree. C. (70.degree. F.) prior to being passed into the bed of activated carbon.There is also disclosed an improved process for the oxidation of a polymethylbenzene to its corresponding aromatic polycarboxylic acid, which process comprises producing the polycarboxylic acid and waste gas comprising methyl acetate, water vapor, and unreacted polymethylbenzene and treating the waste gas according to the above method.

Abstract: There is provided a process for the partial oxidation of a polymethylbenzene to the corresponding aromatic polycarboxylic acid, which process comprises contacting in a reaction zone said polymethylbenzene with molecular oxygen in the presence of an oxidation catalyst comprising at least one heavy-metal compound, said heavy-metal compound being acetate free, a source of bromine, and a non-metal acetate compound, the concentration of acetate in the reaction zone being employed to control the rate of oxidation and the selectivity of oxidation.There is also provided the catalyst that is employed in the process.