METHOD OF CONTINUOUS PREPARATION OF METHIONINE OR SALTS THEREOF Russian patent published in 1998 - IPC

FIELD: food industry. SUBSTANCE: methionine is used as feed additive, more particularly as aqueous solution. Methionine is prepared by direct saponification of methionine-nitriles to produce methionine amide in the presence of ketone and saponification of amide with base. During and/or after saponification of amide, mixture of ammonia, ketone and water is removed at higher or equal to 85 C and/or vacuum. Methionine nitrile is used which is prepared by reacting methilmercaptopropione aldehyde (MMP) with hydrocyanic acid and ammonia or by reacting the corresponding cyanhydrine (CH) with ammonia or by reacting any mixture of MMP with hydrocyanic acid and the corresponding cyanhydrine with ammonia. Said method is carried out without isolation of intermediate products continuously at minimum losses. The ketone used is recuperated with high yield after saponification of amide, and it contains no reaction by-products. Ammonia is separated from ketone, and the resulting mixture of ammonia, ketone and water is separated in column under pressure. If amide is saponified at higher or equal to 160 C, preferable amide concentration is higher or equal to 25 wt%. Methionine nitrile is prepared by treatment of at least 4 equivalents of higher or equal to 50 wt % ammonia at temperature from 40 to 80 C for from 5 to 60 min. Cyanide residue is destructed by heating to temperature higher than 150 C. EFFECT: more efficient continuous preparation method. 17 cl, 1 dwg, 1 tbl