Method of preparing trifluoromethanesulfonic acid anhydride

摘要

(CF3SO2)2O is formed by reaction of CF3SO3H with P2O5 and taken out of the reaction system by distillation, but the residue of the distillation contains a considerable amount of unreacted CF3SO3H. From the residue unreacted by adding water or a phosphoric acid solution, preferably the latter, to the residue to obtain a fluidic mixture containing an adequate amount of water and subjecting the mixture to distillation, preferably under reduced pressure at temperatures ranging from 180 DEG to 280 DEG C. It is possible to form additional CF3SO3H during the recovery process by adding a metal salt of CF3SO3H to the aformentioned mixture since the metal salt is decomposed by phosphoric acid contained in the mixture.