Degussa Aktiengesellschaft

Friedhelm Geiger

Herbert Tanner

Klaus Huthmacher

Jurgen Martens

Friedrich Bittner

Hans-Joachim Hasselbach

Klaus Hentschel

Manfred Spindler

Jose Vanrobaeys

Martin Korfer

Sven-Peter Mannsfeld

Baudouin Halsberghe

Klaus Willigerodt

Ferdinand Theissen

Gerd Schreyer

Werner Heimberger

Horst Hillenbrand

Gerhard Bach

A process for the preparation of methionine or a salt of methionine by reaction of the components 3-methylmercaptopropionaldhyde, hydrogen cyanide, ammonia and carbon dioxide or components from which the above-mentioned components can be prepared, optionally in the presence of water, to 5-(2-methylmercaptoethyl)-hydantoin and further reaction thereof to methionine or the salt thereof, characterised in that the reaction of the components is initiated by means of at least one premixture in such a way that a first mixture is formed containing at least the predominant proportion (at least 5/10) of the 3-methylmercaptopropionaldeyde and at least 1/10 of the hydrogen cyanide component or corresponding quantities of components from which these components can be prepared, and less than 5/10 of one of the components ammonia, carbon dioxide or of the components from which ammonia or carbon dioxide can be prepared, and in that this first mixture is combined with the other component(s) for the reactive conversion to 5-(2-methylmercaptoethyl)-hydantoin, wherein this (these) latter component(s) may be premixed in one or more other mixtures.

Process for the preparation of D,L-methionine or the salt thereof

The residual gases obtained in the production of cyanuric chloride having a pressure of 1-5 bar (absolute) preferably 1-4 bar, are worked up by leading them into the lower portion of a column, reacted in the column with at least the equivalent amount of hydrogen cyanide to form cyanogen chloride and led in countercurrent flow to the water charged to the upper portion of the column whereupon the aqueous solution of cyanogen chloride formed is withdrawn from the lower portion of the column and preferably is returned into the production portion of the plant for recovery of the cyanogen chloride while the purified waste gas of the column leaves in the upper portion of the column.

Working up of the residual gases resulting from the production of

Aqueous sodium methioninate solutions having a low content of sodium carbonate can be recovered from the crude hydrolysis mixture resulting from the saponification of 5-(.beta.-methylmercaptoethyl)hydantoin with 1.1 to 6 equivalents of sodium hydroxide and/or sodium carbonate by cooling the crude hydrolysis mixture to a temperature below 10.degree. C., separating off the precipitated sodium carbonate and concentrating the sodium methioninate solution remaining to 40 to 65 weight percent.

Process for the production of aqueous sodium methioninate solutions

Aqueous sodium methioninate solutions having a low content of sodium carbonate can be recovered from the crude hydrolysis mixture resulting from the saponification of 5-(.beta.-methylmercaptoethyl)-hydantoin with 1.1 to 6 equivalents of sodium hydroxide and/or sodium carbonate by distilling off the water from the crude hydrolysis mixture until the sodium methioninate content is 40 to 65 weight percent, and after cooling to at most room temperature separating off the precipitated sodium carbonate.

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Erlensee, Germany

Friedhelm Geiger