Method for separating ammonium sulfate and ammonium bisulfate from each other and process for producing 2-hydroxy-4-methylthiobutanoic acid utilizing the method

摘要

A process for producing 2-hydroxy-4-methylthiobutanoic acid which includes conducting hydration and successive hydrolysis of 2-hydroxy-4-methylthiobutyronitrile in a reaction system containing 2-hydroxy-4-methylthiobutyronitrile and sulfuric acid, ammonium bisulfate being added to the reaction system at the time of the hydration and/or the hydrolysis, acquiring 2-hydroxy-4-methylthiobutanoic acid from the resulting organic layer, adding a water-miscible organic solvent to the by-produced aqueous layer to deposit ammonium sulfate, and separating and removing the ammonium sulfate from ammonium bisulfate, thereby permitting recycling and reusing of ammonium bisulfate, reduces the amount of sulfuric acid used, produces substantially no waste water containing sulfates and is of a low production cost and environmentally friendly.