This disclosure provides for catalyst systems and processes for forming an α,β-unsaturated carboxylic acid or a salt thereof. In an aspect, the catalyst system can comprise: a transition metal precursor comprising a Group 8-11 transition metal and at least one first ligand; optionally, at least one second ligand; an olefin; carbon dioxide (CO.sub.2); a diluent; and an oxoacid anion-substituted polyaromatic resin comprising a sulfonated polyaromatic resin, a phosphonated polyaromatic resin, a sulfinated polyaromatic resin, a thiosulfonated, or a thiosulfinated polyaromatic resin, and further comprising associated metal cations. Methods of regenerating the polyaromatic resin with associated metal cations are described.

The present invention provides a method for producing an oxide catalyst containing antimony, comprising a step (A) of obtaining the oxide catalyst using antimony particles containing a diantimony trioxide as a source of the antimony, wherein an abundance of a pentavalent antimony in a surface layer of the antimony particle to be measured in XPS analysis is less than 70 atom %, and the antimony particle has an average particle size of 1.2 μm or less.

The present invention provides a method for producing an oxide catalyst containing antimony, comprising a step (A) of obtaining the oxide catalyst using antimony particles containing a diantimony trioxide as a source of the antimony, wherein an abundance of a pentavalent antimony in a surface layer of the antimony particle to be measured in XPS analysis is less than 70 atom %, and the antimony particle has an average particle size of 1.2 μm or less.

The present invention provides a method for producing an oxide catalyst containing antimony, comprising a step (A) of obtaining the oxide catalyst using antimony particles containing a diantimony trioxide as a source of the antimony, wherein an abundance of a pentavalent antimony in a surface layer of the antimony particle to be measured in XPS analysis is less than 70 atom %, and the antimony particle has an average particle size of 1.2 μm or less.

A method is described for producing a catalyst having a high raw material conversion rate and a high product selectivity, as well as an excellent yield of unsaturated carboxylic acid, the catalyst being used in a vapor-phase catalytic oxidation reaction for producing an unsaturated carboxylic acid such as acrylic acid or methacrolein from an unsaturated aldehyde such as acrolein or methacrolein. The method includes a molding process of molding a powder containing a catalyst component element to produce a catalyst precursor, where a sulfur-containing inorganic compound is added to the powder, and the powder is molded in the molding process.

A method is described for producing a catalyst having a high raw material conversion rate and a high product selectivity, as well as an excellent yield of unsaturated carboxylic acid, the catalyst being used in a vapor-phase catalytic oxidation reaction for producing an unsaturated carboxylic acid such as acrylic acid or methacrolein from an unsaturated aldehyde such as acrolein or methacrolein. The method includes a molding process of molding a powder containing a catalyst component element to produce a catalyst precursor, where a sulfur-containing inorganic compound is added to the powder, and the powder is molded in the molding process.

A process can be used for producing methacrylic acid or a methacrylic acid ester. The process involves producing acrolein, reacting the produced acrolein with hydrogen to produce propanal, reacting the propanal with formaldehyde to produce methacrolein, and oxidizing the methacrolein in the presence of an oxygen containing gas and optionally an alcohol, to obtain methacrylic acid or methacrylic acid ester.

A process can be used for producing methacrylic acid or a methacrylic acid ester. The process involves producing acrolein, reacting the produced acrolein with hydrogen to produce propanal, reacting the propanal with formaldehyde to produce methacrolein, and oxidizing the methacrolein in the presence of an oxygen containing gas and optionally an alcohol, to obtain methacrylic acid or methacrylic acid ester.

A catalyst has a modified silica support and comprises a modifier metal, zirconium and/or hafnium, and a catalytic metal on the modified support. The catalyst has at least a proportion, typically, at least 25%, of modifier metal present in moieties having a total of up to 2 modifier metal atoms. The moieties may be derived from a monomeric and/or dimeric cation source. A method of production:— provides a silica support with isolated silanol groups with optional treatment to provide isolated silanol groups (—SiOH) at a level of <2.5 groups per nm.sup.2; contacting the optionally treated silica support with a monomeric zirconium or hafnium modifier metal compound to effect adsorption onto the support; optionally calcining the modified support for a time and temperature sufficient to convert the monomeric zirconium or hafnium compound adsorbed on the surface to an oxide or hydroxide of zirconium or hafnium in preparation for catalyst impregnation.

A catalyst has a modified silica support and comprises a modifier metal, zirconium and/or hafnium, and a catalytic metal on the modified support. The catalyst has at least a proportion, typically, at least 25%, of modifier metal present in moieties having a total of up to 2 modifier metal atoms. The moieties may be derived from a monomeric and/or dimeric cation source. A method of production:— provides a silica support with isolated silanol groups with optional treatment to provide isolated silanol groups (—SiOH) at a level of <2.5 groups per nm.sup.2; contacting the optionally treated silica support with a monomeric zirconium or hafnium modifier metal compound to effect adsorption onto the support; optionally calcining the modified support for a time and temperature sufficient to convert the monomeric zirconium or hafnium compound adsorbed on the surface to an oxide or hydroxide of zirconium or hafnium in preparation for catalyst impregnation.