Method and apparatus for preparing purified terephthalic acid

Details Method and apparatus for preparing purified terephthalic acid Method and apparatus for preparing purified terephthalic acid

1997-10-31

1998-11-24

Barts, Samuel

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

Organic compounds

Carboxylic acids and salts thereof

562486, C07C 5142

Patent

active

058409688

ABSTRACT:
A method and apparatus for purifying crude terephthalic acid from a liquid dispersion thereof also containing impurities selected from unreacted starting materials, solvents, products of side reactions and/or other undesired materials is provided. The method comprises the steps of filtering the dispersion to form a crude terephthalic acid filter cake, dissolving the filter cake in a selective crystallization solvent at an elevated temperature to form a solution, crystallizing purified terephthalic acid from the solution in the crystallization solvent by reducing the pressure and temperature of the solution, and separating the crystallized purified terephthalic acid from the solution. According to the invention, the selective crystallization solvent is non-aqueous, non-corrosive and essentially non-reactive with terephthalic acid. Preferably, the selective crystallization solvent is N-methyl pyrrolidone or dimethyl acetamide. The method and apparatus produces purified terephthalic acid having a purity desired for use in forming polyester resin and other products at an economically attractive rate and at operating conditions of reduced severity which require a lower capital investment and simplified processing.

REFERENCES:
patent: 5159109 (1992-10-01), Rosen et al.
patent: 5344969 (1994-09-01), Iwane et al.

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