METHOD AND APPARATUS FOR PREPARING PURIFIED TEREPHTHALIC ACID

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 reduci ng the pressure and temperature of the solution, and separating the crystallize d purified terephthalic acid from the solution. According to the invention, the selective crystallization solvent is non-aqueous, non-corrosi ve and essentially non-reactive with terephthalic acid. Preferably, the selective crystallization solvent is N-methyl pyrrolidone or dimethyl acetamide. 7he 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 condition of reduced severity which require a lower capital investment and simplified processing.