METODA PENTRU TRATAREA REZIDUURILOR DE DISTILARE A ESTERILOR SI A FILTRATELOR OBTINUTE IN PROCESUL DE PRODUCERE A DIMETILTEREFTALATULUI

摘要

The dimethylterephthalate (I) is obtd. by oxidn., partic. with atmos. O2, of a mixt. of p-xylene and p-methyltoluate (II) and esterificn. with MeOH of the aromatic carboxylic acid obtd. Esterification is carried out under press. and the reaction mixt. is sepd. by distn. into final prod. and residues contg. crude ester. The crude ester is converted as completely as possible to (I) and (II) by esterificn. with MeOH in the presence of aromatic carboxylic acids. A mixt. comprising 10 pts. wt. distn. residue and aromatic acid to 0.5 pt.wt. MeOH is reacted at 190 degrees - 350 degrees C at a press. of 15-50 atmos. (I) and (II) are then recovered from the reaction mixt. Used in the prepn. of pure (I). Recovery of (I) and (II) from the crude ester residues is effected in yields of 60 wt. % and 20 wt. % resp. (c.f. =40 wt. % total prior methods) In an example, 160g distn. residues and 160g reaction mixt. from oxidn. process were esterified with MeOH for 3 h at 310 degrees C and 31 atmos. The yied of (I) recovered was 52.4 wt. %.