METHOD FOR PRODUCING HIGHLY PURE PYROMELLITIC ANHYDRIDE

摘要

PROBLEM TO BE SOLVED: To provide a method for producing highly pure colorless pyromellitic anhydride almost free from a by-product and having high quality. SOLUTION: The objective pyromellitic anhydride is recovered as purified crystal by dissolving crude pyromellitic acid or crude pyromellitic anhydride in water under heating, cooling the solution to crystallize pyromellitic acid, heating and dehydrating the obtained crystal, evaporating the obtained pyromellitic anhydride and cooling the vapor of the pyromellitic anhydride.