Patent ID: 8026391

Claim:
A method for producing potassium perfluoroalkanesulfonate, comprising the steps of: subjecting an alkanesulfonyl halide compound represented by the general formula: C n H 2n+1 SO 2 X, in which n is an integer of 1 to 3 and X is Cl or F, to electrochemical fluorination in anhydrous hydrogen fluoride, thereby to generate a production gas containing, as the main component, perfluoroalkanesulfonyl fluoride represented by the general formula: C n F 2n+1 SO 2 F in which n is an integer of 1 to 3, (electrochemical fluorination step); reacting the production gas with an aqueous solution of potassium hydroxide, thereby to generate a gas absorbed solution containing a potassium perfluoroalkanesulfonate represented by the general formula: C n F 2n+1 SO 3 K, in which n is an integer of 1 to 3, (gas absorption step); removing potassium fluoride, potassium hydroxide, and potassium sulfate which are impurities contained in the gas absorbed solution, (purification step); and subjecting the aqueous solution from which the impurities are removed to concentration and drying, thereby to obtain potassium perfluoroalkanesulfonate represented by the general formula: C n F 2n+1 SO 3 K, in which n is an integer of 1 to 3, (concentration and collection step), wherein, in the purification step, alkali metal hydroxide or alkaline earth metal hydroxide is added to the gas absorbed solution to allow it to react with the potassium fluoride contained in the gas absorbed solution so as to form a fluoride precipitate and potassium hydroxide, and an acid is further added to precipitate the potassium hydroxide in the solution, and these precipitates are removed by filtration, said acid is selected from the group consisting of sulfuric acid, perfluoroalkanesulfonic acid, and a residue of the reaction solution generated in producing perfluoroalkanesulfonic acid by an acid decomposition reaction, and in the concentration and collection step, the filtrate is subjected to concentration and drying to obtain potassium perfluoroalkanesulfonate.