METHOD AND APPARATUS FOR PRODUCING PURIFIED TEREPHTHALIC ACID

PROBLEM TO BE SOLVED: To provide a method and an apparatus for purifying crude terephthalic acid from a liquid dispersion thereof also containing impurities selected from unreacted starting materials, solvents, products of side reaction and/or other undesired materials. SOLUTION: The method comprises the steps of filtering the dispersion to form a crude terephthalic acid filter cake (F-1), dissolving the filter cake in a selective crystallization solvent at an elevated temperature to form a solution (T-3, T-4), crystallizing purified terephthalic acid from the solution in the crystallization solvent by reducing the temperature of the solution (S-1), and separating the crystallized purified terephthalic acid from the solution (F-2). 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. The method and apparatus produces purified terephthalic acid having purity desired for use in forming a 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. COPYRIGHT: (C)2009,JPO&INPIT