PURIFICATION OF TRIFLUOROMETHANESULFONIC ACID ANHYDRIDE

PROBLEM TO BE SOLVED: To provide a method for efficiently purifying trifluoromethanesulfonic acid anhydride by removing phosphorus oxychloride which is produced, as a by-product, upon producing trifluoromethanesulfonic acid anhydride by reacting trifluoromethanesulfonic acid with phosphine pentachloride or phosphine trichloride and chlorine. SOLUTION: This method comprises the steps of (1) addition of phosphoric acid to 'phosphorus oxychloride'-containing trifluoromethanesulfonic acid anhydride, (2) liquid-separation, and (2) distillation. Trifluoromethanesulfonic acid anhydride, which is useful as a raw material, for example, for medicines, agrochemicals, and various functional materials, and as a catalyst, can be purified by removing phosphorus oxychloride, which is contained in trifluoromethanesulfonic acid anhydride, easily, selectively, and in high yield by using phosphoric acid.