Abstract: The present invention provides a process for preparing 3-(methylthio)propanal which can sufficiently decrease the production of high-boiling impurities as a by-product. The process comprises reacting acrolein and methyl mercaptan in the presence of Allylamines (I), Triallylamines (II), and preferably an optional organic acid. The preferred amount of Allylamines (I) is 0.001 to 0.50 mol per 1 mol of Triallylamines (II).

Abstract: A process for producing methionine advantageously in view of cost, while efficiently recovering useful components, is provided, including the following steps (1) hydrolyzing 5-[2-(methylthio)ethyl]imidazolidine-2,4-dione in the presence of a basic potassium compound; (2) introducing carbon dioxide into the reaction solution obtained in step (1) to thereby precipitate methionine, and separating the resulting slurry into a precipitate and a mother liquor; (3) concentrating the mother liquor obtained in step (2), mixing the resulting concentrate with a lower alcohol, introducing carbon dioxide into the resulting mixture to thereby precipitate methionine and potassium hydrogencarbonate, and separating the resulting slurry into a precipitate and a mother liquor; and (4) concentrating the mother liquor obtained in step (3), treating the resulting concentrate by heating at a temperature of from 150 to 200° C., and recycling the treated solution for use in step (3).

Abstract: A process is provided capable of producing 3-methylthiopropanal with subgeneration of high-boiling impurities being favorably inhibited. The process for producing 3-methylthiopropanal, includes reacting acrolein with methylmercaptan in the presence of a triallylamine compound represented by the formula (I): wherein each of R1 to R3 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. The reaction of acrolein with methylmercaptan is preferably performed further in the presence of an organic acid. The triallylamine compound represented by the formula (I) is preferably used in an amount of from 0.01 to 1.0 mol based on one mole of the organic acid and in an amount of from 0.1 to 2.0 mmoles based on one mole of methylmercaptan.

Abstract: A process for producing methionine, while corrosion of a pipe and a reaction vessel is well inhibited, is provided including the following steps (1) to (3), wherein a content of thiols in 3 -methylthiopropanal is 500 ppm or less, based on the propanal, and a content of hydrogen sulfide in 3-methylthiopropanal is 60 ppm or less, based on the propanal; step (1) in which 3 -methylthiopropanal is reacted with hydrogen cyanide in the presence of a base to give 2 -hydroxy -4-methylthiobutanenitrile; step (2) in which the 2-hydroxy-4-methylthiobutanenitrile obtained in step (1) is reacted with ammonium carbonate to give 5-(?-methylmercaptoethyl) hydantoin; and step (3) in which the 5-(?-methylmercaptoethyl)hydantoin obtained in step (2) is hydrolyzed in the presence of a basic potassium compound to give methionine.

Abstract: The present invention provides a process for preparing 3-(methylthio)propanal which can sufficiently decrease the production of high-boiling impurities as a by-product. The process comprises reacting acrolein and methyl mercaptan in the presence of Allylamines (I), Triallylamines (II), and preferably an optional organic acid. The preferred amount of Allylamines (I) is 0.001 to 0.50 mol per 1 mol of Triallylamines (II).

Abstract: A process for producing methionine advantageously in view of cost, while efficiently recovering useful components, is provided including the following steps: (1) hydrolyzing 5-[2-(methylthio)ethyl]imidazolidine-2,4-dione in the presence of a basic potassium compound; (2) introducing carbon dioxide into the reaction solution obtained in the step (1) to thereby precipitate methionine, and separating the resulting slurry into a precipitate and a mother liquor; (3) concentrating the mother liquor obtained in the step (2), mixing the resulting concentrate with a lower alcohol, introducing carbon dioxide into the resulting mixture to thereby precipitate methionine and potassium hydrogencarbonate, and separating the resulting slurry into a precipitate and a mother liquor; and (4) concentrating the mother liquor obtained in the step (3), treating the resulting concentrate by heating at a temperature of from 150 to 200° C., and recycling the treated solution for use in step (2).

Abstract: A process is provided capable of producing 3-methylthiopropanal with subgeneration of high-boiling impurities being favorably inhibited. The process for producing 3-methylthiopropanal, includes reacting acrolein with methylmercaptan in the presence of a triallylamine compound represented by the formula (I): wherein each of R1 to R3 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. The reaction of acrolein with methylmercaptan is preferably performed further in the presence of an organic acid. The triallylamine compound represented by the formula (I) is preferably used in an amount of from 0.01 to 1.0 mol based on one mole of the organic acid and in an amount of from 0.1 to 2.0 mmoles based on one mole of methylmercaptan.

Abstract: A process for producing methionine advantageously in view of cost, while efficiently recovering useful components, is provided, including the following steps: (1) hydrolyzing 5-[2-(methylthio)ethyl]imidazolidine-2,4-dione in the presence of a basic potassium compound; (2) introducing carbon dioxide into the reaction solution obtained in step (1) to thereby precipitate methionine, and separating the resulting slurry into a precipitate and a mother liquor; (3) concentrating the mother liquor obtained in step (2), mixing the resulting concentrate with a lower alcohol, introducing carbon dioxide into the resulting mixture to thereby precipitate methionine and potassium hydrogencarbonate, and separating the resulting slurry into a precipitate and a mother liquor; and (4) concentrating the mother liquor obtained in step (3), treating the resulting concentrate by heating at a temperature of from 150 to 200° C., and recycling the treated solution for use in step (3).

Abstract: A process for producing methionine, while corrosion of a pipe and a reaction vessel is well inhibited, is provided including the following steps (1) to (3), wherein a content of thiols in 3-methylthiopropanal is 500 ppm or less, based on the propanal, and a content of hydrogen sulfide in 3-methylthiopropanal is 60 ppm or less, based on the propanal; step (1) in which 3-methylthiopropanal is reacted with hydrogen cyanide in the presence of a base to give 2-hydroxy-4-methylthiobutanenitrile; step (2) in which the 2-hydroxy-4-methylthiobutanenitrile obtained in step (1) is reacted with ammonium carbonate to give 5-(?-methylmercaptoethyl)hydantoin; and step (3) in which the 5-(?-methylmercaptoethyl)hydantoin obtained in step (2) is hydrolyzed in the presence of a basic potassium compound to give methionine.

Abstract: A process for producing methionine advantageously in view of cost, while efficiently recovering useful components, is provided including the following steps: (1) hydrolyzing 5-[2-(methylthio)ethyl]imidazolidine-2,4-dione in the presence of a basic potassium compound; (2) introducing carbon dioxide into the reaction solution obtained in the step (1) to thereby precipitate methionine, and separating the resulting slurry into a precipitate and a mother liquor; (3) concentrating the mother liquor obtained in the step (2), mixing the resulting concentrate with a lower alcohol, introducing carbon dioxide into the resulting mixture to thereby precipitate methionine and potassium hydrogencarbonate, and separating the resulting slurry into a precipitate and a mother liquor; and (4) concentrating the mother liquor obtained in the step (3), treating the resulting concentrate by heating at a temperature of from 150 to 200° C., and recycling the treated solution for use in step (2).

Abstract: The present invention provides a process for producing methionine which is advantageous from the viewpoints of cost and wastewater disposal, and which comprises the following steps (1) to (5): (1) a reaction step comprising hydrolysis of 5-[2-(methylthio)ethyl]imidazolidine-2,4-dione in the presence of a basic potassium compound; (2) a first crystallization step comprising introduction of carbon dioxide into the reaction solution obtained in the step (1) to precipitate methionine, and separation of the resultant slurry into a precipitate and a mother liquor; (3) a second crystallization step comprising concentration of the mother liquor obtained in the step (2), mixing with a lower alcohol, introduction of carbon dioxide into the mixture to precipitate methionine and potassium hydrogen carbonate, and separation of the resultant slurry into a precipitate and a mother liquor; (4) a heating step comprising concentration of the mother liquor obtained in the step (3) followed by a heating treatment at 150 to 20