Patent ID: 8217197

Claim:
A process for producing methionine, comprising the following steps (1), (2), (3) and (4): (1) a reaction step of hydrolyzing 5-[2-(methylthio)ethyl]imidazolidine-2,4-dione in the presence of a basic potassium compound; (2) a first crystallization step of introducing carbon dioxide into the reaction solution obtained in the step (1) to thereby precipitate methionine, and separating the resulting slurry into a precipitate and a mother liquor; (3) a second crystallization step of concentrating the mother liquor obtained in the step (2), mixing the resulting concentrate with a lower alcohol, introducing carbon dioxide into the resulting mixture to thereby precipitate methionine and potassium hydrogencarbonate, and separating the resulting slurry into a precipitate and a mother liquor; and (4) a heating step of concentrating the mother liquor obtained in the step (3), treating the resulting concentrate by heating at a temperature of from 150 to 200° C., and recycling the treated solution for use in the step (3).