Method for the continuous preparation of methionine or methionine derivatives

US5672745A · kind A · utility

Assignee

• Degussa AG · DE

Inventors

• Hans-Albrecht Hasseberg · Rodenbach, DE
• Klaus Huthmacher · Gelnhausen, DE
• Stephan Rautenberg · Hanau, DE
• Heinrich Petsch · Hanau, DE
• Horst Weigel · Rodenbach, DE

Key dates

• Filing date: May 23, 1995
• Grant date: Sep 30, 1997
• Expiry date: May 23, 2015

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C319/20
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

The direct saponification of methionine nitrile obtained from methylmercaptopropionaldehyde, prussic acid and ammonia gives low yields, catalyst and educt losses and unwanted side-products. The aim of the invention is therefore to provide a method which can be carried out without isolating the intermediate products, in particular continuously, and with low losses. The ketone used is recovered in high yields after amide saponification since this liberates the ketone from side-products. In order to recover the ammonia, it is necessary for the ammonia to be substantially freed of ketone, the mixture of ammonia, ketone and water obtained being separated under pressure in a separation column. When the amide is saponified at .gtoreq.160.degree. C., amide concentrations of less than 25% by wt. are preferred. Methionine nitrile is produced by treatment with at least 4 equivalents of .gtoreq.50% by wt. ammonia at between 40.degree. and 80.degree. C./or between 5 and 60 min. Cyanide residues are destroyed by heating to over 150.degree. C. Methionine is of particular use as a feedstuff, in particular in aqueous solution.