Process for production of a silica-supported alkali metal catalyst
A process for regenerating a silica-supported depleted alkali metal catalyst is described. The level of alkali metal on the depleted catalyst is at least 0.5 mol % and the silica support is a zero-gel. The process comprises the steps of contacting the silica supported depleted alkali metal catalyst with a solution of a salt of the alkali metal in a solvent system that has a polar organic solvent as the majority component. A re-impregnated catalyst prepared by the process of the invention any comprising a silica zero-gel support and a catalytic metal selected from an alkali metal in the range 0.5-5 mol % on the catalyst, wherein the surface area of the silica support is <180 m 2 /g is also described. The invention is applicable to a process for preparing an ethylenically unsaturated acid or ester comprising contacting an alkanoic acid or ester of the formula R 1 —CH 2 —COOR 3 , with formaldehyde or a suitable source of formaldehyde.
1. A process for regenerating a silica-supported depleted alkali metal catalyst wherein a level of alkali metal on the depleted catalyst is at least 0.5 mol %, and
wherein the silica support is a zero-gel comprising the step of:
contacting said silica supported depleted alkali metal catalyst with a solution of a salt of the alkali metal in a solvent system that has a polar organic solvent as the majority component.
2. The process according to claim 1 , wherein a surface area of the catalyst is <180 m 2 /g.
3. The process according to claim 1 , wherein a bulk of a surface area of the silica is present in pores having a diameter ranging from 5 nm to 150 nm.
4. The process according to claim 3 , wherein a bulk of pore volume of the silica is provided by pores having diameters ranging from 5 nm to 150 nm.
5. The process according to claim 1 , wherein the alkali metal is selected from lithium, sodium, potassium, rubidium, and caesium.
6. The process according to claim 1 , wherein the salt of the alkali metal is selected from the group consisting of acetate, propionate, carbonate, hydrogen carbonate, nitrate, and hydroxide.
7. The process according to claim 1 , wherein the depleted alkali metal catalyst comprises a second metal selected from the group consisting of zirconium, titanium, hafnium, aluminium, boron and magnesium, and mixtures thereof.
8. The process according to claim 1 , wherein the polar organic solvent is an alcohol.
9. The process according to claim 1 , wherein the solution of the alkali metal salt in the solvent system has a starting pH between 8 and 13.
10. The process according to claim 1 , wherein water is present in the solution at up to 40% by weight.
11. The process according to claim 1 , wherein the alkali metal salt in solution is <2 wt %.
12. The process according to claim 1 , wherein an increase in alkali metal on the catalyst following the process is in the range 0.25 to 2.0 mol %.
13. The process according to claim 1 , wherein alkali metal concentration in the solvent system to initially begin impregnation is between 6×10 −3 and 0.6 mol·dm −3 alkali metal in the solution.
14. The process according to claim 1 , wherein the process is carried out at a temperature of 0-100° C.
15. The process according to claim 1 , wherein the process is carried out at a pressure of 1-10 bara.
16. The process according to claim 1 , wherein the catalyst is a fixed bed form during contact with the alkali metal solution.
17. The process according to claim 1 , wherein flow rates for the alkali metal solution in contact with the catalyst are 0.1 to 10 bed volumes/hr.
18. The process according to claim 1 , wherein the catalyst is formed into shaped units having maximum and minimum dimensions in the range 1 to 10 mm.
19. The process according to claim 1 , wherein the process is a liquid phase impregnation process.