PURIFICATION PROCESS FOR AROMATIC ACIDS

1386582 Purification of aromatic acids SUN RESEARCH & DEVELOPMENT CO 19 June 1973 [19 June 1972] 28931/73 Heading C2C An impure aromatic acid is purified by heating it in a three-phase heterogeneous system consisting of an aqueous solution of acetic acid, a liquid aromatic hydrocarbon and the impure aromatic acid, the aqueous acetic acid solution containing 40-65% (wt.) of water, the weight ratio of acetic acid to aromatic acid being from 3À75 : 1 to 20 : 1, from 15 to 90% of the aromatic acid being in the solid phase and said heating being carried out in a closed system at a temperature of 200-250‹ C.; separating the hydrocarbon solvent and isolating the purified acid from the aqueous acetic acid layer. The aromatic acid is a benzene, polycarboxylic or naphthalene mono or polycarboxylic acid. Examples describe the purification of terephthalic acid, isophthalic acid and 2,6-naphthalene dicarboxylic acid.