Abstract: In a method for producing hydrogen cyanide by passing a feed mixture comprising ammonia and methane through reaction tubes, coated on the inner surface with a catalyst comprising platinum, at a reaction temperature of 1000° C. to 1400° C., operated for a time period of at least 100 h, the concentration difference between the ammonia concentration and the methane concentration in the product gas mixture is maintained in a range of from 1.05 % by volume to 3.0% by volume for at least 80% of the time.

Abstract: The present invention relates to a method for preparing methionine or methionine salts. In particular, the invention describes the step of preparing 2-hydroxy-4-(methylthio)butyronitrile (MMP-CN) from 3-methylthiopropanal (MMP) and hydrogen cyanide (HCN) in the presence of ammonia by bringing a gaseous mixture comprising HCN and ammonia into contact with MMP.

Abstract: The present invention relates to a method for preparing methionine or methionine salts. In particular, the invention describes the step of preparing 2-hydroxy-4-(methylthio)butyronitrile (MMP-CN) from 3-methylthiopropanal (MMP) and hydrogen cyanide (HCN) in the presence of ammonia by bringing a gaseous mixture comprising HCN and ammonia into contact with MMP.

Abstract: The reaction tube for preparing hydrogen cyanide comprises a cylindrical tube composed of ceramic, a catalyst comprising platinum applied to the inner wall of the tube and also at least one insert composed of ceramic, having three or four fins pointing from the tube axis to the inner wall of the tube, which is inserted into the cylindrical tube, wherein the fins divide the tube interior space into substantially straight channels with substantially identical circle segment cross sections and wherein the mean gap between the ends of the fins and the inner wall of the tube is in the range of 0.1 to 3 mm. In the method for preparing hydrogen cyanide, ammonia and at least one aliphatic hydrocarbon having 1 to 4 carbon atoms are reacted in the reaction tube at 1000 to 1400° C.

Abstract: In a method for producing hydrogen cyanide by passing a feed mixture comprising ammonia and methane through reaction tubes, coated on the inner surface with a catalyst comprising platinum, at a reaction temperature of 1000° C. to 1400° C., operated for a time period of at least 100 h, the concentration difference between the ammonia concentration and the methane concentration in the product gas mixture is maintained in a range of from 1.05 % by volume to 3.0% by volume for at least 80% of the time.

Abstract: The reaction tube for preparing hydrogen cyanide comprises a cylindrical tube composed of ceramic, a catalyst comprising platinum applied to the inner wall of the tube and also at least one insert composed of ceramic, having three or four fins pointing from the tube axis to the inner wall of the tube, which is inserted into the cylindrical tube, wherein the fins divide the tube interior space into substantially straight channels with substantially identical circle segment cross sections and wherein the mean gap between the ends of the fins and the inner wall of the tube is in the range of 0.1 to 3 mm. In the method for preparing hydrogen cyanide, ammonia and at least one aliphatic hydrocarbon having 1 to 4 carbon atoms are reacted in the reaction tube at 1000 to 1400° C.

Abstract: The reaction tube comprises a cylindrical ceramic tube and a catalyst comprising platinum applied to the inner surface of the tube, wherein the reaction tube has fins on the inner surface which run in the longitudinal direction of the tube, extend into the interior space of the reaction tube and are coated with catalyst. The reaction tube is suitable for preparing hydrogen cyanide by reacting ammonia and at least one aliphatic hydrocarbon having 1 to 4 carbon atoms at a temperature of 1000 to 1400° C.

Abstract: A method to produce D,L-Methionine from 2-hydroxy-4-(methylthio)butyronitrile by reaction with ammonia, optionally in the presence of carbon dioxide, is provided. The 2-hydroxy-4-(methylthio)butyronitrile is obtained by reaction of 3-methylmercaptopropionaldehyde with hydrogen cyanide in the presence of a base as catalyst in a main reaction zone of a multizone reactor. Residual gaseous hydrogen cyanide is removed from the main reaction zone to an absorption and post-reaction zone of the reactor which comprises a mixture of 3-methylmercaptopropionaldehyde and the catalyst; and the gaseous hydrogen cyanide is further reacted with the 3-methylmercaptopropionaldehyde in the absorption and post reaction zone. A molar ratio of hydrogen cyanide to 3-(methylthio)propanal in the main reaction zone is from 0.98 to 1.03.

Abstract: A method for the production of 2-hydroxy-4-methylthiobutyric acid by hydrolysis of 2-hydroxy-4-(methylthio)butyronitrile is provided. 3-Methylmercaptopropionaldehyde is reacted with hydrogen cyanide in the presence of a base as catalyst in a main reaction zone of the multizone reactor to form a reaction mixture comprising the 2-hydroxy-4-(methylthio)butyronitrile, unreacted 3-methylmercaptopropionaldehyde, the catalyst and residual amounts of gaseous hydrogen cyanide. The residual gaseous hydrogen cyanide is removed from the main reaction zone to an absorption and post-reaction zone of the reactor which comprises a mixture of 3-methylmercaptopropionaldehyde and the catalyst; and the gaseous hydrogen cyanide is further reacted with the 3-methylmercaptopropionaldehyde in the absorption and post reaction zone. A molar ratio of hydrogen cyanide to 3-(methylthio)propanal in the main reaction zone is from 0.98 to 1.03.

Abstract: A method to produce D,L-Methionine from 2-hydroxy-4-(methylthio)butyronitrile by reaction with ammonia, optionally in the presence of carbon dioxide, is provided. The 2-hydroxy-4-(methylthio)butyronitrile is obtained by reaction of 3-methylmercapto-propionaldehyde with hydrogen cyanide in the presence of a base as catalyst in a main reaction zone of a multizone reactor. Residual gaseous hydrogen cyanide is removed from the main reaction zone to an absorption and post-reaction zone of the reactor which comprises a mixture of 3-methylmercaptopropionaldehyde and the catalyst; and the gaseous hydrogen cyanide is further reacted with the 3-methylmercaptopropionaldehyde in the absorption and post reaction zone. A molar ratio of hydrogen cyanide to 3-(methylthio)propanal in the main reaction zone is from 0.98 to 1.03.

Abstract: A method for the production of 2-hydroxy-4-(methylthio)butyronitrile having good storage stability in a multi-zone reactor, is provided. 3-methylmercaptopropionaldehyde is reacted with hydrogen cyanide in the presence of a base as catalyst in a main reaction zone of the multizone reactor to form a reaction mixture comprising the 2-hydroxy-4-(methylthio)butyronitrile, unreacted 3-methylmercaptopropionaldehyde, the catalyst and residual amounts of gaseous hydrogen cyanide. The residual gaseous hydrogen cyanide is removed from the main reaction zone to an absorption and post-reaction zone of the reactor which comprises a mixture of 3-methylmercaptopropionaldehyde and the catalyst; and the gaseous hydrogen cyanide is further reacted with the 3-methylmercaptopropionaldehyde in the absorption and post reaction zone. A molar ratio of hydrogen cyanide to 3-(methylthio)propanal in the main reaction zone is from 0.98 to 1.03.

Abstract: A method for the production of 2-hydroxy-4-(methylthio)butyronitrile having good storage stability in a multi-zone reactor, is provided. 3-methylmercaptopropionaldehyde is reacted with hydrogen cyanide in the presence of a base as catalyst in a main reaction zone of the multizone reactor to form a reaction mixture comprising the 2-hydroxy-4-(methylthio)butyronitrile, unreacted 3-methylmercaptopropionaldehyde, the catalyst and residual amounts of gaseous hydrogen cyanide. The residual gaseous hydrogen cyanide is removed from the main reaction zone to an absorption and post-reaction zone of the reactor which comprises a mixture of 3-methylmercaptopropionaldehyde and the catalyst; and the gaseous hydrogen cyanide is further reacted with the 3-methylmercaptopropionaldehyde in the absorption and post reaction zone. A molar ratio of hydrogen cyanide to 3-(methylthio)propanal in the main reaction zone is from 0.98 to 1.03.

Abstract: A storage stable mixture containing 86 to 97% by weight of 2-hydroxy-4-methylthiobutyronitrile, 2 to 14% by weight of water, 0.05 to 0.5% by weight of HCN and having a pH of 1 to 4, measured using a pH electrode at 23° C. is provided. A method to produce the storage stable mixture and its use in manufacture of DL-methionine or 2-hydroxy-4-methylthiobutyric acid is also provided.

Abstract: A method for the production of 2-hydroxy-4-(methylthio)butyronitrile having good storage stability in a multi-zone reactor, is provided. 3-methylmercaptopropionaldehyde is reacted with hydrogen cyanide in the presence of a base as catalyst in a main reaction zone of the multizone reactor to form a reaction mixture comprising the 2-hydroxy-4-(methylthio)butyronitrile, unreacted 3-methylmercaptopropionaldehyde, the catalyst and residual amounts of gaseous hydrogen cyanide. The residual gaseous hydrogen cyanide is removed from the main reaction zone to an absorption and post-reaction zone of the reactor which comprises a mixture of 3-methylmercaptopropionaldehyde and the catalyst; and the gaseous hydrogen cyanide is further reacted with the 3-methylmercaptopropionaldehyde in the absorption and post reaction zone. A molar ratio of hydrogen cyanide to 3-(methylthio)propanal in the main reaction zone is from 0.98 to 1.03.

Abstract: A storage stable mixture containing 86 to 97% by weight of 2-hydroxy-4-methylthiobutyronitrile, 2 to 14% by weight of water, 0.05 to 0.5% by weight of HCN and having a pH of 1 to 4, measured using a pH electrode at 23° C. is provided. A method to produce the storage stable mixture and its use in manufacture of DL-methionine or 2-hydroxy-4-methylthiobutyric acid is also provided.