METHOD OF GAINING AND REINTRODUCING THE OXIDATION CATALYSER IN PROCESS OF PRODUCING THE DIMETHYL TEREPHTALATE IN THE OXIDATION

摘要

A process for effecting the recovery and use of a heavy metal oxidation catalyst from a high-boiling distillation residue obtained during the Witten process for the production of dimethyl terephthalate involves the extraction of the high-boiling distillation reside with water or dilute aqueous solution of low molecular weight aliphatic monocarboxylic acids or alcohols and recycling of the extract into the oxidation stage of the Witten process. In the extract the quantitative ratio of the sum of the amount of trimellitic acid and monomethyl ester of trimellitic acid to the amount of heavy metal catalyst is controlled to be at a value of no more than 1.8:1 and in the oxidation stage of the Witten process the catalyst concentration (c), expressed in p.p.m., is represented by the formula: c=44x(a/b)+d wherein a represents the sum of trimellitic acid and monomethyl ester of trimellitic acid, b is the amount of heavy metal oxidation catalyst within the extract, and d is in a range of from 60 to 300 p.p.m.