C - Chemistry – Metallurgy – 07 – C
Patent
C - Chemistry, Metallurgy
07
C
260/511.2
C07C 63/26 (2006.01) C07C 51/09 (2006.01)
Patent
CA 1134857
ABSTRACT OF THE DISCLOSURE: The invention is concerned with a process for the preparation of fiber-grade terephthalic acid from an inter- mediate stage crude dimethyl terephthalate obtained from a crude ester mixture produced by the oxidation of p-xylene and/or methyl p-toluate with oxygen-containing gases in the presence of heavy-metal-containing oxidation catalysts at an elevated temperature and under an elevated pressure, and by the esterification of the oxidation mixture with methanol at elevated temperature and elevated pressure. The process of the invention comprises separating the resulting crude ester mixture by distillation into a methyl p-toluate-enriched fraction, a residual high boiling fraction, and also a crude dimethyl terephthalate having a limited content of the inter- mediate oxidation products and other by-products; subsequently hydrolyzing the crude dimethyl terephthalate with water at a weight ratio of the crude dimethyl terephthalate to water of between 3 : l and 0.1 ; l, and at temperatures of between 140°C. and 350°C. and under the pressure required to maintain the liquid phase to produce a reaction mixture containing crystalline fiber-grade terephthalic acid, and then recovering the terephthalic acid from the reaction mixture. The invention enables one to produce directly from a crude DMT, a terephthalic acid, suitable for manufacturing polyester fibers, by means of hydrolysis, without the step of recrystallization of the crude DMT from methanol customary in the Katzschmann process or of a corresponding step of recrystallization of the thus-obtained terephthalic acid.
342255
Schoengen Anton
Schreiber Georg
Schroeder Heinz
Dynamit Nobel Aktiengesellschaft
Robic Robic & Associes/associates
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