CRYSTALLIZATION-MEDIATED ISOPHTHALIC ACID PURIFICATION Russian patent published in 2003 - IPC

FIELD: industrial organic synthesis. SUBSTANCE: isophthalic acid suitable for copolymerization processes is produced by oxidation of m-xylene in reaction solvent until liquid dispersion is obtained. invention, in particular, relates to purification of crude isophthalic acid from its liquid dispersion also containing impurities including unreacted starting substances, solvent, reaction by-products, and/or other undesired materials. Purification procedure: filtration of dispersion to give crude isophthalic acid in the form of cake; dissolving this cake in selective crystallization solvent at elevated temperature (within a range of about 50 to 200 C); crystallization of isophthalic acid from thus obtained solution by lowering temperature or lowering pressure to a value sufficient for instant distillation of solvent from isophthalic acid solution; separation of thus purified isophthalic acid from solution; washing cake of purified isophthalic acid with pure or isophthalic acid-saturated solvent to displace mother solution and colorants; and redissolving or soaking washed isophthalic acid cake in water at elevated temperatures. Purified product contains less than 40 ppm 3-carboxybenzaldehyde and less than 2 ppm m-tolylic acid the balance. EFFECT: increased degree of purification. 25 cl, 1 dwg, 2 tbl, 2 ex