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.

Abstract: A method for producing allyl chloride is provided which includes: a chlorination step of reacting propylene with chlorine to obtain a reaction product containing allyl chloride, unreacted propylene and by-product hydrogen chloride; a separation step of cooling the reaction product to separate the reaction product into the allyl chloride and a mixed gas containing the unreacted propylene and the by-product hydrogen chloride; a collection step of separating the mixed gas into the unreacted propylene and the by-product hydrogen chloride to collect the unreacted propylene; and an oxidation step of oxidizing the separated by-product hydrogen chloride to obtain chlorine. At least part of the chlorine used in the chlorination step is the chlorine obtained in the oxidation step. A method for producing dichlorohydrin using the chlorine obtained in the oxidation step is also provided.

Abstract: An object of the present invention is to provide a novel method for producing chlorine, by which it is possible to remove impurities contained with hydrogen chloride in a raw material gas and further to recover unreacted hydrogen chloride after an oxidation reaction efficiently in a method for producing chlorine by oxidizing hydrogen chloride.

Abstract: An object of the present invention is to provide a novel method for producing chlorine with improved efficiency, which can remove impurities other than hydrogen chloride contained in a raw material gas and can recover unreacted hydrogen chloride after an oxidation reaction efficiently.

Abstract: Provided is a method of purifying hydrochloric acid by removing an organic substance having a boiling point of ?25° C. to 120° C. under atmospheric pressure from an organic substance-containing hydrochloric acid that contains the organic substance and has a hydrogen chloride concentration higher than an azeotropic hydrogen chloride concentration under atmospheric pressure. The method includes the step of subjecting the organic substance-containing hydrochloric acid to distillation using a distillation tower at an operation pressure set such that an azeotropic hydrogen chloride concentration under the operation pressure is higher than the hydrogen chloride concentration of the organic substance-containing hydrochloric acid, to distill out the organic substance from the top of the distillation tower.

Abstract: Provided is a method of purifying hydrochloric acid by removing an organic substance having a boiling point of ?25° C. to 120° C. under atmospheric pressure from a first organic substance-containing hydrochloric acid that contains the organic substance and has a hydrogen chloride concentration higher than an azeotropic hydrogen chloride concentration under atmospheric pressure. The method includes the step of subjecting a second organic substance-containing hydrochloric acid to distillation using a distillation tower under atmospheric pressure, to distill out the organic substance from a top of the distillation tower. The second organic substance-containing hydrochloric acid is obtained by mixing the first organic substance-containing hydrochloric acid and water or dilute hydrochloric acid and has the hydrogen chloride concentration lower than the azeotropic hydrogen chloride concentration under atmospheric pressure.

Abstract: Disclosed is a process for producing chlorine, which makes it possible to successfully continue an oxidation reaction, even if sulfur component-containing hydrogen chloride is used. This process comprises a step of feeding sulfur component-containing hydrogen chloride and oxygen into a reaction tube 1 comprising a catalyst packed bed 10, to thereby oxidize the hydrogen chloride to produce chlorine, wherein the catalyst packed bed 10 includes an alumina-mixed catalyst packed bed 20 formed of a mixture of a catalyst 3 with alumina (or a diluent 4), and wherein the BET specific surface area of the alumina is from 10 to 500 m2/g. Preferably, the alumina is ?-alumina and/or ?-alumina.

Abstract: Disclosed is a process for producing chlorine by oxidation of hydrogen chloride through a catalytic gas-phase reaction in the presence of a catalyst, wherein hydrogen chloride as a raw material is a by-product of synthesis of isocyanate by reacting phosgene and primary amine and oxidizing the hydrogen chloride through a catalytic gas phase reaction in the presence of a catalyst. The process is characterized by adjusting the sulfur content in carbon monoxide which is a raw material for the phosgene to 2000 vol. ppb or less.

Abstract: Provided is a hydrogen chloride oxidation reaction apparatus for producing chlorine by oxidizing hydrogen chloride through a contact gas phase reaction in the presence of a catalyst by using hydrogen chloride and oxygen as major raw materials, wherein the hydrogen chloride oxidation reaction apparatus includes a mixing portion for mixing the raw material gases and a transfer piping portion for transferring the mixed raw material gases from the mixing portion to a reactor for a contact gas phase reaction, and wherein a gas contact surface of the mixing portion and/or a part of a gas contact surface of the transfer piping is made of or covered with tantalum or a tantalum-tungsten alloy, as well as a hydrogen chloride oxidation reaction method using the same.