METHOD OF PRODUCING METHIONINE Russian patent published in 2003 - IPC

FIELD: chemical purification of sewage water and other media. SUBSTANCE: method of producing methionine from 5-β-methylmercaptoethyl)hydantoin involves two stages: (A) adding at least one compound selected from the group, comprising potassium carbonate, potassium bicarbonate and potassium hydroxide, to solution comprising 5-(β-methylmercaptoethyl)hydantoin so that ratio between hydantoin and at least one of said compounds is 1:1 and 1:5, at temperature of from 120 C to 220 C for producing methionine- containing solution; (B) saturating resultant solution with gaseous carbon dioxide and separating settled methionine for obtaining first filtrate; (C) dividing first filtrate into first and second parts, directing first part back to stage (A) and transferring part or whole amount of first filtrate to stage (D); (D) heating transferred first filtrate, adding water- miscible solvent and saturating it with gaseous carbon dioxide for settling of methionine and potassium bicarbonate and separating sediments thereof for obtaining second filtrate after separation; and (E) directing, when needed, second filtrate back to stage (A). Method allows methionine dimer available in the system to be effectively used and, as a result, methionine yield to be increased. EFFECT: increased efficiency by reduced loading of sewage water and eliminating increase in contaminants and dyed substance content in reaction system, and simplified extraction of methionine and potassium bicarbonate. 7 cl, 3 tbl, 7 ex