Patent ID: 6054610
Filing Date: 2000-04-25
Classification: C07C,Y02P

Abstract:
A method for purifying crude terephthalic acid (Tfrom a liquid dispersion produced from the oxidation of mixed xylenes comprising:(a) dissolving the crude TPA in a selective crystallization solvent at a temperature of from about 50.degree. C. to about 250.degree. C. to form a solution;(b) crystallizing purified acid from said solution by reducing the temperature and/or pressure thereof;(c) separating said crystallized purified TPA from said solution;(d) redissolving said separated purified TPA in a selective crystallization solvent to form a second solution;(e) crystallizing second stage purified TPA from said second solution by reducing the temperature and pressure sufficient to flash evaporate solvent from said TPA of said second solution but without cooling said solution below 50.degree. C.;(f) separating said second stage purified TPA from said second solution;(g) washing said separated second stage purified TPA with water;(h) soaking said washed separated second stage purified TPA with water at a temperature between about 150.degree. C. and about 300.degree. C.;(i) filtering and drying said water soaked second stage purified T(j) adding an anti-solvent to said filtered solution in (c) to cause the precipitation of substantially all the Tand(k) separating said precipitated TPA from said solution in (j) and combining said precipitated TPA with said original crude TPA for processing in (a);(l) evaporating the solvents from said filtered TPA-free solution in (k) to cause the crystallization of IPA at a temperature from about 5.degree. C. and about 100.degree. C.;(m) separating said crystallized crude IPA from said solution in (1);(n) redissolving crude IPA in a selective crystallization solvent at a temperature from about 500.degree. C. to 250.degree. C. to form a second solution;(o) crystallizing purified IPA from said second solution in (n) by reducing the temperature and pressure sufficient to flash evaporate solvent from said IPA of said second solution but without cooling said solution below about 50.degree. C.; and(p) separating and drying said second stage purified IPA from said second solution.