Di:methyl terephthalate prepn. - by liquid phase oxidn. of para-xylene or derivs., esterification, distn. and residue treatment with oxygen and methanol (NL 31.1.78)

摘要

Dimethyl terephthalate is prepd. by (1) liquid-phase oxidn. of p-xylene, Me p-toluate and p-tolualdehyde with O2 or an O2-contg. gas in the presence of a heavy metal catalyst (2) prod. esterification with MeOH and (3) esterified prod. distn. to separate dimethyl terephthalate and cpds. boiling below dimethyl terephthalate, with formation of a distn. residue. (4) Distn. residue is contacted with MeOH and O2 or an O2-contg. gas. esp. air under O2 partial press. =0.2 (=4)=kg/cm2 at 140-350 (180-330) esp. 200-300 degrees C in the presence of =10 ppm Mn cpd. (calculated as Mn metal wrt. distn. residue), and (5) dimethyl terephthalate and its intermediate products e.g. Me-p-toluate, p-toluic acid, Me p-formyl benzoate, monomethyl terephthalate and terephthalic acid, are recovered. Dimethyl terephthalate is a starting material in polyester prodn. Dimethyl terephthalate yields are increased.