METHOD FOR MANUFACTURING HIGH-PURITY PYROMELLITIC ACID AND HIGH-PURITY PYROMELLITIC ANHYDRIDE

摘要

PROBLEM TO BE SOLVED: To provide a method for manufacturing high-quality, high-purity pyromellitic acid and high-purity pyromellitic anhydride which are colorless and almost free from byproducts. SOLUTION: High-purity pyromellitic acid is manufactured by dissolving crude pyromellitic acid or crude pyromellitic anhydride in water by heating, treating the resulting solution with activated carbon and subsequently cooling the solution to precipitate crystals followed by filtration. Further, the obtained high-purity pyromellitic acid is converted to its anhydride by heating at 170-260 deg.C to manufacture high-purity pyromellitic anhydride.