Process for producing highly pure terephthalic acid

Details Process for producing highly pure terephthalic acid Process for producing highly pure terephthalic acid

1996-09-03

1998-01-06

Barts, Samuel

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic acids and salts thereof

562413, C07C 5116

Patent

active

057056820

ABSTRACT:
A process for producing highly pure terephthalic acid comprising: (a) oxidizing a p-phenylene compound in the liquid phase in the presence of acetic acid, to produce a liquid-phase oxidation product, (b) separating the liquid-phase oxidation product into the following: (i) a first mother liquid containing acetic acid and (ii) a crude terephthalic acid, (c) evaporating, in whole or in part, the first mother liquid, to produce a vapor, (d) feeding the vapor, or a condensate thereof, to an intermediate stage of a distillation tower, carrying out an azeotropic distillation and withdrawing through a bottom of the distillation tower a concentrated acetic acid, (e) subjecting the crude terephthalic acid to a refining treatment, which is a catalytic hydrotreatment, a catalytic treatment or a recrystallization, which is carried out in the presence of is water, (f) cooling and crystallizing the resultant liquid from step (e), to produce a pure terephthalic acid and a second mother liquor, (g) subjecting the second mother liquor to an extraction in the presence of an azeotrope-forming agent to extract aromatic carboxylic acids contained in second mother liquor, to produce a liquid extract, and (h) recycling the liquid extract to the distillation tower in step (d). The process can greatly reduce the effluent water treatment load and enhance the yield of the objective terephthalic acid, in addition to providing recycling of useful reactants.

REFERENCES:
patent: 4939297 (1990-07-01), Browder et al.

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