Chemische Werke Huls Aktiengesellschaft

Norbert Wilke

Ferdinand List

Horst-Dieter Wulf

Kurt Wember

Friedrich-August Orlowski

Emmerich Pflegerl

Wilfried Uhlenbrock

Dimethyl terephthalate is prepared by the continuous esterification of terephthalic acid in the gas phase by evaporating solid terephthalic acid in a pre-reactor by means of a hot methanol vapor stream, conducting the gas mixture through a solid bed catalyst in a follow-up reactor, and recirculating a portion of the reaction product to the pre-reactor. After the pre-reactor the terephthalic acid dispersed in the methanol gas phase is heated and vaporized in one or more consecutive heat exchangers followed by one or more dwell period lengths and immediately heated to the esterification temperature prior to entry into the follow-up reactor.

Apparatus for the esterification of terephthalic acid in the gas phase

The process of recovering methanolic mother liquor obtained by the esterification of terephthalic acid with methanol, where the terephthalic acid may be unprepurified, is improved by adjusting to a specific gravity of about 0.85 - 0.98 by addition of water and/or methanol distillate, a mother liquor containing esterification water and dissolved solids at a concentration of about 1.0 to 6.0 percent by weight and cooling the mother liquor from a temperature of about 65.degree. - 85.degree. C to a temperature of about 10.degree. - 30.degree. C to separate the solids and remove the separated solids. The separated solids may be recycled into the esterification reaction and the unseparated solids may be recycled for oxidation to terephthalic acid following distillation to remove the methanol.

Process for recovering the mother liquor produced by the esterification

Dimethyl terephthalate is prepared by the continuous esterification of terephthalic acid in the gas phase by evaporating solid terephthalic acid in a pre-reactor by means of a hot methanol vapor stream, conducting the gas mixture through a solid bed catalyst in a follow-up reactor, and recirculating a portion of the reaction product to the pre-reactor.

Apparatus for the production of dimethyl terephthalate by the

Process for the esterification of terephthalic acid in the gas phase

Dimethyl terephthalate prepared by the esterification of terephthalic

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Marl, Germany

Norbert Wilke