Process for production of isophthalic acid

A method for producing isophthalic acid, comprising:

• subjecting a m-phenylene compound and a molecular-oxygen-containing gas to liquid-phase oxidation reaction in the presence of a catalyst comprising a heavy metal compound and a bromine compound, and hydrous acetic acid having a water content of 1 to 15 mass %, to thereby yield a slurry;
• regulating the temperature of the slurry to 35 to 140° C., to thereby precipitate isophthalic acid;
• removing the isophthalic acid through solid-liquid separation, to thereby recover a mother liquor;
• and
• recovering the catalyst from the mother liquor by following (1) to (4) for reusing at least a portion of the catalyst in the liquid-phase oxidation reaction:
• (1) regulating the ratio of an amount by mole of bromide ions in the mother liquor over total amount by mole of heavy metal ions in the mother liquor to 0.3 to 3, and then exposing the mother liquor to a pyridine-ring-containing chelate resin which is heated to 35 to 140° C., wherein the resin adsorbs catalyst-derived heavy metal ions and bromide ions, and also adsorbs a by-produced carboxylic acid mixture which is produced by the liquid-phase oxidation reaction,
• (2) (A) yielding an eluate comprising the by-produced carboxylic acid mixture by exposing hydrous acetic acid having a water content of 1 to 15 mass to the pyridine-ring-containing chelate resin which is processed by (1),
• (3) (B) yielding an eluate comprising catalyst-derived heavy metal ions and bromide ions by exposing water or hydrous acetic acid having a water content of 20 mass % or more to the pyridine-ring-containing chelate resin which is processed by (A), and
• (4) exposing hydrous acetic acid having a water content of 1 to 15 mass % to the pyridine-ring-containing chelate resin which is processed by (B), serving as a displacement liquid, thereby regenerating the resin.