Process for the preparation of terephthalic acid by the hydrolysis of intermediate stage crude dimethyl terephthalate

Abstract From the Canadian patent

The invention is concerned with a process for the preparation of fiber-grade terephthalic acid from an intermediate stage crude dimethyl terephthalate obtained from a crude ester mixture produced by the oxidation of p-xylene and/or methyl p-toluate with oxygen-containing gases in the presence of heavy-metal-containing oxidation catalysts at an elevated temperature and under an elevated pressure and by, the esterification of the oxidation mixture with methanol at elevated temperature and elevated pressure. The process of the invention comprises separating the resulting crude ester mixture by distillation into a methyl p-toluate-enriched fraction, a residual high boiling fraction and also a …