Abstract: Disclosed is a method for producing an ?, ?-unsaturated carboxylic acid from an olefin or an ?, ?-unsaturated aldehyde, while suppressing dissolution of a silica carrier, which is a carrier for a silica-supported noble metal-containing catalyst, in a water-containing solvent. Specifically disclosed is a method for producing an ?, ?-unsaturated carboxylic acid through oxidation of an olefin or an ?, ?-unsaturated aldehyde in a water-containing solvent in the presence of a silica-supported noble metal-containing catalyst in a reactor, in which at least one of silicic acid and ions thereof is supplied into the reactor.

Abstract: Disclosed is a method for extracting methacrylic acid, in which an extraction solvent is added to a methacrylic acid aqueous solution for transferring methacrylic acid to the extraction solvent. In this method, a solvent containing t-butyl methacrylate is used as the extraction solvent.

Abstract: Disclosed is a method for enhancing a yield of an ?,?-unsaturated carboxylic acid obtained by liquid-phase oxidation reaction of an olefin or an ?,?-unsaturated aldehyde. In particular, there is provided a method for producing an ?,?-unsaturated carboxylic acid, wherein the method includes the step of carrying out oxidation reaction of an olefin or an ?,?-unsaturated aldehyde in a liquid phase to obtain a reaction mixture containing an ?,?-unsaturated carboxylic acid and an ?,?-unsaturated carboxylic acid anhydride and the step of bringing the ?,?-unsaturated carboxylic acid anhydride into contact with an alcohol or water to obtain an ?,?-unsaturated carboxylic acid resulting from decomposition of the ?,?-unsaturated carboxylic acid anhydride.

Abstract: Disclosed is a method for extracting methacrylic acid, in which an extraction solvent is added to a methacrylic acid aqueous solution for transferring methacrylic acid to the extraction solvent. In this method, a solvent containing t-butyl methacrylate is used as the extraction solvent.

Abstract: Disclosed is a method for producing an ?, ?-unsaturated carboxylic acid from an olefin or an ?, ?-unsaturated aldehyde, while suppressing dissolution of a silica carrier, which is a carrier for a silica-supported noble metal-containing catalyst, in a water-containing solvent. Specifically disclosed is a method for producing an ?, ?-unsaturated carboxylic acid through oxidation of an olefin or an ?, ?-unsaturated aldehyde in a water-containing solvent in the presence of a silica-supported noble metal-containing catalyst in a reactor, in which at least one of silicic acid and ions thereof is supplied into the reactor.

Abstract: Disclosed is a method for producing an ?,?-unsaturated carboxylic acid by oxidizing an olefin or an ?,?-unsaturated aldehyde in a liquid phase in the presence of a noble metal catalyst, which can ensure operational safety at the time of stopping the reaction and prevent deterioration of the noble metal catalyst. The method for producing the ?,?-unsaturated carboxylic acid by an oxidation reaction in which the olefin or the ?,?-unsaturated aldehyde is oxidized in the liquid phase in the presence of the noble metal catalyst in a reactor, includes a step of stopping the oxidation reaction by supplying an inert gas to the reactor.

Abstract: Disclosed is a method for enhancing a yield of an ?,?-unsaturated carboxylic acid obtained by liquid-phase oxidation reaction of an olefin or an ?,?-unsaturated aldehyde. In particular, there is provided a method for producing an ?,?-unsaturated carboxylic acid, wherein the method includes the step of carrying out oxidation reaction of an olefin or an ?,?-unsaturated aldehyde in a liquid phase to obtain a reaction mixture containing an ?,?-unsaturated carboxylic acid and an ?,?-unsaturated carboxylic acid anhydride and the step of bringing the ?,?-unsaturated carboxylic acid anhydride into contact with an alcohol or water to obtain an ?,?-unsaturated carboxylic acid resulting from decomposition of the ?,?-unsaturated carboxylic acid anhydride.