Dimethyl terephthalate prepared by the esterification of terephthalic acid
AssigneeChemische Werke Huls Aktiengesellschaft
InventorsHorst-Dieter Wulf, Ferdinand List, Kurt Wember, Norbert Wilke
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Abstract
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.
Claims9
In the continuous method for the preparation of dimethyl terephthalate by the esterification of terephthalic acid with methanol in the gas phase, comprising vaporizing solid terephthalic acid with a hot methanol vapor stream in a pre-reactor and introducing the reaction product of the pre-reactor into a follow-up reactor having a solid bed catalyst to produce a hot gaseous dimethyl terephthalate product stream, part of this stream being the output of the process the improvement comprising recirculating a portion of said dimethyl terephthalate product stream to said pre-reactor.
A continuous method for the preparation of dimethyl terephthalate by the esterification of terephthalic acid with methanol in the gas phase at a temperature of about 290.degree.-330.degree.C, comprising:
- a. vaporizing solid terephthalic acid with a hot methanol vapor stream in a pre-reactor in a ratio of terephthalic acid to methanol of about 1:3 by weight;
- b. introducing the reaction product of the pre-reactor into a follow-up reactor having a solid bed granular esterification catalyst and producing a hot gaseous dimethyl terephthalate product stream having a given volume;
- and
- c, recirculating c. portion of said hot gaseous dimethyl terephthalate product stream to said pre-reactor of step (a) wherein the volume ratio of said portion to the remainder of said given volume is about 0.5:1 to 5:1 and heating said recirculated portion at a temperature of about 250.degree. to 350.degree.C.
Dependencies are inferred from the claim text.