Patent ID: 7547803

Claim:
A process for producing a high purity aromatic polycarboxylic acid selected from the group consisting of naphthalenepolycarboxylic acids and biphenylpolycarboxylic acids by purifying a crude aromatic polycarboxytic acid selected from the group consisting of crude naphthalenepolycarboxylic acids and crude biphenylpolycarboxylic acids, respectively, which comprises: (I), in a step of aging, aging a slurry comprising the crude aromatic polycarboxylic acid in a first dispersion medium under heating at 210 to 290° C. for 10 minutes or longer while being stirred; (II), in a step of substituting dispersion media, introducing the slurry comprising the aromatic polycarboxylic acid which has been treated by aging under heating into a column for substituting dispersion media, bringing the slurry into contact with a second dispersion medium and separating a resultant fluid into a fluid of the first dispersion medium and a slurry of the second dispersion medium comprising crystals of the aromatic polycarboxylic acid; and (III), in a step of separating crystals, separating the crystals of the aromatic polycarboxylic acid from the slurry of the second dispersion medium.