Process for the separation of the raw ester mixture from the production of dimethylterephthalate by the Witten-Hercules process

摘要

A process for separating the crude ester mixture (CEM) from the production of dimethyl terephthalate (DMT) by the Witten- Hercules process, comprising continuous distillation in at least one column in which DMT is separated from the residue and/or low- boiling components, and into which methanol is introduced, thus combining separation with methanolysis. Preferably methanol may be injected indirectly into one or more columns via a circulation system equipped with a heat exchanger, optionally together with vaporised products from the depressurised CEM, and/or directly or indirectly into the bottom of at least one of the columns. The methanol is injected as vapour, especially as the vaporised methanol obtained when the CEM is depressurised after leaving the esterification reactor.