Method for making silica supported, crush-resistant catalysts
View Patent ↗A method for making a silica supported catalyst involves impregnating a silica component with a catalytic metal using an aqueous, alkaline bath before drying. More specifically, the method involves forming and washing a silica component, such as a silica gel or a co-gel, for example a silica-zirconia co-gel. Then, the washed silica component is contacted with the alkaline bath to effect the impregnation with the catalytic metal, such as cesium, to form an activated silica component. Subsequently, the activated silica component is dried to form the catalyst. The resulting catalysts demonstrate good mechanical strength.
1. A method for making a catalyst comprising the steps of:
forming a silica component, wherein the silica component is a silica hydrogel;
washing said silica hydrogel;
contacting said silica hydrogel with an aqueous, alkaline bath comprising a catalytic metal selected from the group consisting of an alkali metal and an alkaline earth metal to impregnate said silica hydrogel with said catalytic metal to form an activated silica hydrogel; and
drying said activated silica hydrogel to form said catalyst.
2. The method in accordance with claim 1 , wherein said alkaline bath has a pH of between about 7.5 and 10 at the end of the metal impregnation.
3. The method in accordance with claim 2 , wherein said alkaline bath has a pH of between about 8 and 9.5 at the end of the metal impregnation.
4. The method in accordance with claim 1 , wherein said alkaline bath further comprises a salt of said catalytic metal and ammonium hydroxide.
5. The method in accordance with claim 4 , wherein said catalytic metal is cesium and said salt is cesium carbonate.
6. The method in accordance with claim 1 , wherein the step of forming said silica hydrogel comprises mixing an alkali metal silicate with a mineral acid to form a hydrosol and allowing said hydrosol to set.
7. The method in accordance with claim 1 , wherein said silica hydrogel comprises a co-gel and the step of forming said co-gel comprises combining an alkali metal silicate, a mineral acid, and a source of a second metal to form a hydrosol and allowing said hydrosol to set.
8. The method in accordance with claim 7 , wherein the combining step comprises first mixing said mineral acid with said source of said second metal to form a mixture then combining said alkali metal silicate with said mixture.
9. The method in accordance with claim 7 , wherein said second metal is selected from the group consisting of zirconium, titanium, aluminum and Fe.
10. The method in accordance with claim 9 , wherein said second metal is zirconium and said source of zirconium is zirconium orthosulfate.
11. The method in accordance with claim 1 , wherein the washing step comprises acidifying said silica hydrogel and then washing said acidified silica hydrogel with acidified water.
12. The method in accordance with claim 11 , wherein the pH of said acidified silica hydrogel is about 1.5 to 2.5, and th pH of said acidified water is about 2.5 to 4.
13. The method in accordance with claim 1 , wherein the washing step comprises washing said silica hydrogel with an aqueous ammonium sulfate solution then with neutral water.
14. The method in accordance with claim 1 further comprising, prior to the washing step, heating said silica hydrogel in an alkaline hydrothermal solution.
15. The method in accordance with claim 1 further comprising calcining said dried catalyst.
16. The method in accordance with claim 1 , wherein said alkaline bath further comprises ammonium hydroxide.
17. The method in accordance with claim 1 , wherein said catalytic metal is an alkali metal.
18. A method for making a catalyst comprising the steps of:
combining an alkali metal silicate, a mineral acid, and a source of zirconium to form a hydrosol and allowing said hydrosol to set to form a co-gel;
washing said co-gel;
contacting said co-gel with an aqueous, alkaline bath comprising cesium to impregnate said co-gel with said cesium to form an activated silica co-gel, wherein said bath has a pH between and 8 and 9.5 at the end of the metal impregnation; and
drying said activated silica co-gel to form said catalyst.