Process for the purification of crude terephthalic acid from a liquid dispersion of it that also contains selected impurities among non-reactive starting materials, solvents, secondary reaction products and/or other unwanted materials

摘要

PROCEEDINGS FOR THE PURIFICATION OF SUCCESSFUL TERPHABETICAL ACID OF A LIQUID DISCHARGE WHICH ALSO CONTAINS SELECTED IMPRISES BETWEEN RELATED PARTY MATERIALS NOT REACTED, SOLVENTS, SECONDARY REACTION PRODUCTS AND/OR OTHER INDESTED MATERIALS." A process and apparatus for the purification of crude terephthalic acid from a liquid dispersion of it also contains selected impurities between non-reactive starting materials, solvents, secondary reaction products and/or other unwanted materials are provided. The process comprises the dispersion filtration steps to form a crude terephthalic acid filter pie,dissolution of filter pie in a solvent for selective crystallization at a high temperature to form a solution, crystallization of terephthalic acid purified from solution in crystallisation solvent by reduction of pressure and solution temperature and separation from said purified crystallised terephthalic acid solution. According to the invention, the solvent is non-aqueous, non-corrosive and essentially non-reactive with terephthalic acid. Preferably,the solvent for selective crystallization is N-methyl pyrrolidone or N,N-dimethyl acetamide. The process and apparatus produce purified terephthalic acid that has a desired purity for use in the formation of polyester resin and other products at an economically attractive speed and the condition of reduced gravity operation requiring less capital investment and simplified processing.