Abstract: The present invention provides a method for purifying carbon dioxide gas characterized in that carbon dioxide gas containing at least one of 3-methylmercaptopropionaldehyde and acrolein is contacted with activated carbon to remove at least one of the 3-methylmercaptopropionaldehyde and acrolein. The present invention provides also a method for producing methionine comprising the purification step of the recovered carbon dioxide.

Abstract: The present provides a method for producing methionine which is characterized by a crystallization step in which carbon dioxide is introduced into a reaction solution containing an alkali salt of methionine which is obtained by hydrolyzing 5-[2-(methylthio)ethyl] imidazoline-2,4-dione in the presence of an alkali compound, thereby precipitating the methionine, and further comprises a step of adding waste methionine to the reaction solution. The method of production of the present invention can improve a yield in the production of methionine.

Abstract: The present provides a method for producing methionine which is characterized by a crystallization step in which carbon dioxide is introduced into a reaction solution containing an alkali salt of methionine which is obtained by hydrolyzing 5-[2-(methylthio)ethyl] imidazoline-2,4-dione in the presence of an alkali compound, thereby precipitating the methionine, and further comprises a step of adding waste methionine to the reaction solution. The method of production of the present invention can improve a yield in the production of methionine.

Abstract: The present invention provides a method for producing methionine characterized by comprising a step of hydrolyzing 5-[2-(methylthio)ethyl]imidazolidine-2,4-dione in the presence of an alkali compound to obtain a reaction solution containing an alkali salt of methionine, a step of precipitating methionine by introducing carbon dioxide into the reaction solution to obtain a first slurry containing the methionine, a step of allowing the first slurry to flow into a pressurized filter and obtaining the solid methionine and mother liquor from the first slurry, and a step of recovering carbon dioxide from the mother liquor. By the present production method, the carbon dioxide introduced in the crystallization step is suppressed from being released from the mother liquor, and the carbon dioxide can be recovered.

Abstract: The present invention provides a method for purifying carbon dioxide gas characterized in that carbon dioxide gas containing at least one of 3-methylmercaptopropionaldehyde and acrolein is contacted with activated carbon to remove at least one of the 3-methylmercaptopropionaldehyde and acrolein. The present invention provides also a method for producing methionine comprising the purification step of the recovered carbon dioxide.

Abstract: The present invention provides a method for producing methionine which is characterized by comprising (1) a reaction step: a step of hydrolyzing 5-[2-(methylthio)ethyl]imidazolidine-2,4-dione in the presence of an alkali compound to obtain a reaction solution containing an alkali salt of methionine, (2) a first crystallizing step: a step of introducing carbon dioxide into the reaction solution and precipitating methionine from the reaction solution to obtain the first crystal of methionine and the first crystal mother liquor, and (3) a second crystallizing step: a step in which after obtaining a slurry which contains precipitates containing the second crystals of methionine precipitated by introducing carbon dioxide to the first crystal mother liquor and the slurry was subjected to centrifugation to separate the second crystal of methionine and the second crystal mother liquor by a solid-liquid separation, and the precipitate remained in the obtained second crystal mother liquor is separated using a filter.

Abstract: The present invention provides a method for producing methionine characterized by comprising a step of hydrolyzing 5-[2-(methylthio)ethyl]imidazolidine-2,4-dione in the presence of an alkali compound to obtain a reaction solution containing an alkali salt of methionine, a step of precipitating methionine by introducing carbon dioxide into the reaction solution to obtain a first slurry containing the methionine, a step of allowing the first slurry to flow into a pressurized filter and obtaining the solid methionine and mother liquor from the first slurry, and a step of recovering carbon dioxide from the mother liquor. By the present production method, the carbon dioxide introduced in the crystallization step is suppressed from being released from the mother liquor, and the carbon dioxide can be recovered.