Di:methyl terephthalate prodn. from methyl para:toluate - by oxidn. in liquid phase contg. some methanol and esterification of obtd. acids to reduce by=product formation

摘要

Prodn. of dimethyl terephthalate (I) by oxidn. of methyl p-toluate (II), opt. mixed with p-xylene (III), is carried out in the liq. phase at elevated pressure and temp. in the presence of a low-mol. aliphatic alcohol, using (gas contg.)O2 in the presence of oxidn. catalysts, followed by esterification of the acids formed with MeOH and sepn. of the esterification prods. The novelty is that, during oxidn., the liq. phase is treated with Me OH in an amt. insufficient for significant esterification, so that a MeOH concn. of 400-0000 (700-2000) ppm is maintained in this phase. Pref. oxidn. is carried out in stages in a series of oxidn. reactors and the MeOH concn. is controlled separately in each stage. (I) is used as raw material in the mfr. of fibre- and film-forming polyesters. No solvents or hydrocarbon cpds. are used and the amt. of volatile acids and of high boiling residues, which cannot be converted to (I) and (II), formed is less than usual, without the oxidn. of harmful amts. of MeOH.