Patent ID: 6455731
Filing Date: 2002-09-24
Classification: C07C

Abstract:
A process for producing a high purity aromatic polycarboxylic acid by purifying a crude aromatic polycarboxylic acid in accordance with (I) a step of forming a salt which comprises forming an amine salt of an aromatic polycarboxylic acid from the crude polycarboxylic acid and an amine, (II) a step of decomposing a salt which comprises (i) conducting in a salt decomposition reactor operations of supplying an aqueous solution of the amine salt of an aromatic polycarboxylic acid formed in the step of forming a salt, (ii) removing the amine and water by distillation under heating and (iii) taking out a slurry containing crystallized aromatic polycarboxylic acid, and (III) a step of separating crystals which comprises separating and recovering crystals of the aromatic polycarboxylic acid from the slurry which is taken out in the step of decomposing a salt, whereinin the step of decomposing a salt, the slurry in the salt decomposition reactor which comprises the aqueous solution of the amine salt and the aromatic polycarboxylic acid formed by the decomposition is circulated through a heat exchanger, heat is supplied in the heat exchanger while a pressure of the slurry is kept at a vapor pressure of the slurry or higher, wherein the pressure of the slurry in the heat exchanger being kept higher than the vapor pressure of the slurry at a temperature at an outlet of the heat exchanger and a difference in the pressure being in a range of +0.02 MPa to +0.5 MPa, a mixture of the amine and water is removed by distillation in the salt decomposition reactor, and the aromatic polycarboxylic acid is crystallized in the salt decomposition reactor.