PRODUCTION OF HIGH-PURITY 2-ACRYLAMIDE-2-METHYLPROPANESULFONIC ACID

PURPOSE:To efficiently obtain the high-purity subject compound by washing crude 2-acrylamide-2-methylpropanesulfonic acid with water-containing acrylonitrile having high water content. CONSTITUTION:Excess acrylonitrile which is used as both of a raw material and a reaction solvent is made to react with a prescribed amount of sulfuric acid or fuming sulfuric acid and isobutylene to provide crude acrylamide-2- methylpropanesulfonic acid separated and deposited in a crystalline state from the reaction mixture. The crude crystal is, preferably right after being separated and obtained, washed with acrylonitrile having >=1.0wt.%, preferably >=2.0wt.% acrylonitrile and dried at 30-140 deg.C according to ordinary method to provide the objective compound as a powdery high-purity crystal. An amount of acrylonitrile used for washing is preferably 0.5-5 pts.wt. especially 1-3 pts.wt. based on 1 pts. crude crystal.