Production of unsaturated acids or esters thereof and catalysts therefor

A catalyst comprising a porous high surface area silica containing 1-10% by weight of an alkali metal (expressed as metal), wherein the catalyst contains a mixture of compounds of modifier elements selected from boron, magnesium, aluminium, zirconium and/or hafnium in such amount that the catalyst contains a total of 0.25 to 2 gram atoms of said modifier elements per 100 moles of silica, said modifier element compound being dispersed in the pores of said silica.

A catalyst as claimed in any preceding claim, wherein the compound of at least one modifier element is present in the form of at least one oxide and/or hydroxide of said at least one modifier element.

A catalyst comprising a porous high surface area silica containing 1-10% by weight of an alkali metal (expressed as metal), wherein the catalyst contains a compound of at least one modifier element selected from boron, magnesium, aluminium, zirconium and hafnium in such amount that the catalyst contains a total of 0.25 to 2 gram atoms of said modifier element per 100 moles of silica, said modifier element compound being dispersed in the pores of said silica, wherein where the catalyst contains only boron as a modifier element it excludes boron up to a level of 0.29 gram atoms of said modifier element per 100 moles of silica.

A catalyst comprising a porous high surface area silica containing 1-10% by weight of an alkali metal (expressed as metal), wherein the catalyst contains a compound of boron as a modifier element in such amount that the catalyst contains a total of 0.39 to 3.9 gram atoms of said modifier element per 100 moles of silica, said modifier element compound being dispersed in the pores of said silica.

A method of preparing a catalyst comprising mixing together particles of a porous high surface area silica with a solution of a mixture of compounds of modifier elements selected from boron, magnesium, aluminium, zirconium and/or hafnium such that said compounds are impregnated into said particles in such amount that the particles contain a total of 0.25 to 2 gram atoms of said modifier element per 100 moles of silica;

• impregnating said particles with a solution of a compound of an alkali metal such that the particles contain 1-10% by weight of said alkali metal (expressed as metal), said impregnation being carried out before during or after the impregnation with the modifier element compounds;
• and subsequently drying said particles.

A method of preparing a catalyst comprising mixing together particles of a porous high surface area silica with a solution of a compound of a modifier element selected from magnesium, aluminium, zirconium and/or hafnium such that said compound is impregnated into said particles in such amount that the particles contain a total of 0.25 to 2 gram atoms of said modifier element per 100 moles of silica;

• impregnating said particles with a solution of a compound of an alkali metal such that the particles contain 1-10% by weight of said alkali metal (expressed as metal), said impregnation being carried out before during or after the impregnation with the modifier element compound;
• and subsequently drying said particles.

A method of preparing a catalyst comprising mixing together particles of a porous high surface area silica with a solution of a compound of a modifier element boron, such that said compound is impregnated into said particles in such amount that the particles contain a total of 0.39 to 3.9 gram atoms of said modifier element per 100 moles of silica;

• impregnating said particles with a solution of a compound of an alkali metal such that the particles contain 1-10% by weight of said alkali metal (expressed as metal), said impregnation being carried out before during or after the impregnation with the modifier element compound;
• and subsequently drying said particles.