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 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 of formula I as defined below:
where R 5 is methyl and R 6 is H;
X is O;
n is 1;
and m is 1;
in the presence of a re-impregnated catalyst, and optionally in the presence of an alkanol; wherein R 1 is hydrogen or an alkyl group with 1 to 12 carbon atoms and R 3 is independently, hydrogen or an alkyl group with 1 to 12 carbon atoms, wherein the re-impregnated catalyst comprises a silica zero-gel support having a surface area of <180 m 2 /g, and a catalytic metal selected from an alkali metal ranging from 0.5 to 5 mol % on the re-impregnated catalyst and wherein the re-impregnated catalyst has been depleted prior to being re-impregnated.
2. The process according to claim 1 , wherein the ethylenically unsaturated acid or ester is selected from methacrylic acid, acrylic acid, methyl methacrylate, ethyl acrylate, or butyl acrylate.
3. The process according to claim 1 , wherein the ester or acid of formula R 1 —CH 2 —COOR 3 is methyl propionate or propionic acid.
4. The process according to claim 1 , wherein the alkanol is methanol.
5. The process according to claim 1 , wherein the process is conducted at a molar ratio of acid or ester to formaldehyde from 20:1 to 1:20, and at a temperature of 250-400° C. with a residence time of 1-100 seconds, and at a pressure of 1-10 bara.
6. The process according to claim 1 , wherein the re-impregnated catalyst is prepared by a process of contacting a silica supported depleted alkali metal catalyst with a solution of a salt of the alkali metal in a solvent system having a polar organic solvent as a majority component.
7. A re-impregnated catalyst comprising:
a silica zero-gel support and
a catalytic metal selected from an alkali metal ranging from 0.5 to 5 mol % on the catalyst, wherein: a surface area of the silica support is <180 m 2 /g and wherein the re-impregnated catalyst has been depleted prior to being re-impregnated.
8. The re-impregnated catalyst of claim 7 , wherein the re-impregnated catalyst is prepared by a process of contacting a silica supported depleted alkali metal catalyst with a solution of a salt of the alkali metal in a solvent system having a polar organic solvent as a majority component.
9. The re-impregnated catalyst of claim 7 , wherein the catalytic metal is selected from an alkali metal ranging from 5 to 10 wt % on the catalyst.