Process for the production of ethylenically unsaturated carboxylic acids or esters and a catalyst therefor
A method of producing an ethylenically unsaturated carboxylic acid or ester such as (meth) acrylic acid or alkyl esters thereof, for example, methyl methacrylate is described. The process comprises the steps of contacting formaldehyde or a suitable source thereof with a carboxylic acid or ester, for example, propionic acid or alkyl esters thereof in the presence of a catalyst and optionally an alcohol. The catalyst comprises group II metal phosphate crystals having rod or needle like morphology or a suitable source thereof. The phosphate may be a hydroxyapatite, pyrophosphate, hydroxyphosphate, PO 4 2− phosphate or mixtures thereof. The group II metal may be selected from Ca, Sr, Ba or mixtures thereof, for example, strontium hydroxyapatite and calcium hydroxyapatite. A catalyst system comprising a crystalline metal phosphate catalyst and a catalyst support is also described. The metal phosphate has rod/needle like morphology.
1. A catalyst system for the reaction of formaldehyde or a suitable source thereof with a carboxylic acid or ester comprising a crystalline metal phosphate catalyst and a catalyst support wherein the metal phosphate has rod/needle like morphology.
2. The catalyst system according to claim 1 , wherein the phosphate is selected from the group consisting of pyrophosphate, hydroxyphosphate, PO 4 3− phosphate and mixtures thereof.
3. The catalyst system according to claim 2 , wherein the phosphate is selected from the group consisting of pyrophosphate, hydroxyapatite, and mixtures thereof.
4. The catalyst system according to claim 1 , wherein the phosphate is selected from the group consisting of Ca, Sr or Ba or mixtures thereof.
5. The catalyst system according to claim 1 , wherein the catalysts are selected from the group consisting of strontium hydroxyapatite and calcium hydroxyapatite.
6. The catalyst system according to claim 1 , wherein the catalyst is at least 50% w/w metal phosphate.
7. The catalyst system according to claim 1 , wherein the catalyst has a surface layer of crystals depleted below a metal:phosphorus (M:P) mole ratio of 1.67.
8. The catalyst system according to claim 7 , wherein the crystal surface metal:phosphorus (M:P) mole ratio is between 1.30 and 1.55.
9. The catalyst system according to claim 1 , wherein doping elements are present in the catalyst at a level of up to 20 mol % of the metal M.
10. The catalyst system according to claim 9 , wherein the doping elements are metal cations selected from the group consisting of Cs, K, Rb, Na, Li, Zn, Ti, Si, La, Ce, Eu, Mg if not used as a group II metal, Ba if not used as a group II metal, Pb, Cd, Ag, Co, Cu, Ni and Zr.
11. The catalyst system according to claim 1 , wherein doping anions are present in the catalyst at a level of up to 20 mol % phosphate.
12. The catalyst system according to claim 11 , wherein the doping anions are selected from the group consisting of carbonate, chloride and fluoride.
13. The catalyst system according to claim 1 , wherein the catalyst is on a support selected from the group consisting of alumina, silica, silicon nitride, silicon carbide, colloidal silica, titania or aluminium phosphate.
14. The catalyst system according to claim 1 , wherein the metal:phosphorus (M:P) mole ratio is between 0.8-1.8.