Abstract: A method for regenerating a phosphorus-, molybdenum- and alkali metal-containing oxidation catalyst spent in the production of an unsaturated carboxylic acid by vapor-phase oxidation of an unsaturated aldehyde, which comprises treating the deactivated catalyst with aqueous ammonia and an aqueous solution containing at least one of a nitrogen-containing heterocyclic compound, an amine, and ammonium carbonate, followed by drying and calcining the treated catalyst.

Abstract: A process for improving the operating characteristics of a phosphorous-, molybdenum-, and oxygen-containing catalyst used for the production of an unsaturated carboxylic acid by gas phase catalytic oxidation of a corresponding unsaturated aldehyde, comprising the step of calcinating the catalyst at a temperature of 300.degree.-500.degree. C. while a gas containing 0.05-3 vol. % of ammonia and/or steam is passed over the catalyst.

Abstract: This disclosure relates to a process for the purification of 2-acrylamido-2-methylpropanesulfonic acid, which comprises dissolving said sulfonic acid in hydrous acetic acid of a water content of 3 to 80% by weight at 60.degree. to 110.degree. C. and subjecting the resulting solution to recrystallization. The purified product thus obtained is useful particularly as a starting material in preparing a high-molecular-weight polymer or copolymer.

Abstract: This disclosure relates to a process for preparing highly pure 2-acylamido-2-methylpropanesulfonic acid, which comprises the steps of adding acetic acid to a slurry containing crystals of 2-acrylamido-2-methylpropanesulfonic acid obtained by the reaction of acrylonitrile, isobutene and either conc. sulfuric acid, fuming sulfuric acid or sulfuric anhydride plus water in a solvent, then distilling the resulting mixture to replace the reaction solvent with acetic acid, adding water or hydrous acetic acid to the resulting mixture, heating the mixture to dissolve said crystals, and subjecting the solution to recrystallization.