PROCESS FOR MANUFACTURING A DIMETHYLTEREPHTHALATE INTERMEDIATE PRODUCT OF GIVEN PURITY, SUBSEQUENT PROCESSING THEREOF TO OBTAIN ULTRAPURE DIMETHYLTEREPHTHALATE AND/OR MEDIUM OR HIGH-PURITY TEREPHTHALIC ACID

摘要

The DMT intermediate product is manufactured by joint oxidation of a mixture containing predominantly para-xylol (p-X) and para-toluene acid methyl ester (p-TE) in a liquid phase with a gas containing oxygen. The acids produced are esterified with methanol, and the esterification products are separated into a fraction rich in p-TE, a fraction containing more than 99 weight percent of DMT and its isomers and a residue fraction with a high boiling point, and the p-TE fraction is recycled to the oxidation. The residue fraction has a DMT content of 15 to 70 weight percent and the DMT fraction is purified by simple solvent recrystallisation in methanol to yield the DMT intermediate product in which the methyl hydroxy benzoate and methyl terephthalate together amount to less than 200 ppm.