| 摘要 |
Dimethyl terephthalate is purified by passing a stream of preheated toluene, xylene or tetrahydronaphthalene vapour through the molten ester whereby it distils over at atmospheric pressure without appreciable decomposition or sublimation. The introduced vapours are preferably preheated to a temperature of 200-255 DEG C. The ester distils over with the vapour at 250-260 DEG C. and is cooled to yield a hard crystal magma which is flaked, washed with a pure aromatic compound, e.g. toluene, and dried. In the example toluene vapour preheated to 255 DEG C. is passed through molten dimethyl terephthalate kept at 270-273 DEG C. A mixture of ester (75 per cent) and toluene (25 per cent) distils over and is condensed on cooled rollers. The solid ester is flaked, washed with pure toluene and dried. |
