Catalyst having metal in reduced quantity and reduced cluster size
The invention contemplates a method of making a catalytic material, and uses of the material. The catalytic material is made by depositing catalytic metals, such as gold or platinum, on substrate materials, such as lanthanum-doped ceria or other oxides. The catalytic metal, which comprises both crystalline and non-crystalline structures, is treated, for example with aqueous basic NaCN solution, to leach away at least some of the crystalline metallic component. The remaining noncrystalline metallic component associated with the substrate exhibits catalytic activity that is substantially similar to the catalyst as prepared. The use of the catalyst in an apparatus such as a reactor or analytic instrument is contemplated, as is the use of the catalyst in efficient, cost-effective reactions, such as removal of carbon monoxide from fuel gases, for example by performing the water gas shift reaction.
1. A method of preparing a catalyst material, comprising the steps of:
providing a substrate component having a surface;
producing on said surface of said substrate component a second component having metallic crystalline particles and a structure lacking crystallinity; and
removing selectively from said surface of said substrate component at least some of said metallic crystalline particles, leaving associated with said substrate component at least a portion of said structure lacking crystallinity;
whereby said remaining structure lacking crystallinity associated with said substrate component exhibits catalytic activity.
2. The method of claim 1 , wherein said catalytic activity of said remaining structure lacking crystallinity and said substrate component is substantially equal to a catalytic activity exhibited by said catalyst material prior to said selective removal of crystalline particles.
3. The method of claim 1 , wherein the step of providing said substrate component comprises forming said substrate by a gelation/coprecipitation process followed by calcining.
4. The method of claim 1 , wherein the step of producing on said surface of said substrate component a metallic component comprises applying said metallic component by a process selected from precipitation, co-precipitation, gelation, evaporation, a deposition-precipitation process, an impregnation process, adsorption of molecules followed by decomposition, ion implantation, chemical vapor deposition, and physical vapor deposition.
5. The method of claim 1 , wherein said substrate component comprises a microcrystalline substance.
6. The method of claim 1 , wherein said substrate component is sintered at a temperature of approximately 400 degrees Centigrade.
7. The method of claim 1 , wherein said substrate component comprises a selected one of a rare-earth-, an alkaline earth-, a Sc- or a Y-doped cerium oxide.
8. The method of claim 7 , wherein said rare-earth is lanthanum.
9. The method of claim 1 , wherein said metallic component comprises an element selected from the group consisting of Au, Pt, Cu, Rh, Pd, Ag, Fe, Mn, Ni, Co, Ru, and Ir.
10. The method of claim 1 , wherein said removal step comprises a process selected from the group consisting of leaching, etching, and dissolving.
11. The method of claim 1 , wherein said removal step comprises leaching with a solution of NaCN.
12. The method of claim 11 , wherein said removal step comprises leaching with an aqueous solution of 2 mole percent NaCN having a pH of at least 8.
13. The method of claim 1 , wherein said removal step removes at least 10% of the original quantity of said metallic component.
14. The method of claim 1 , wherein said removal step removes at least 25% of the original quantity of said metallic component.
15. The method of claim 1 , wherein said removal step removes at least 50% of the original quantity of said metallic component.
16. The method of claim 1 , wherein said removal step removes at least 90% of the original quantity of said metallic component.
17. The method of claim 1 , wherein said catalytic activity is exhibited in the performance of a water gas shift reaction.
18. The method of claim 1 , wherein said substrate comprises an oxide.
19. The method of claim 1 , wherein said substrate comprises a selected one of a zeolite, a carbide, a nitride, a sulfate, and a sulfide.
20. The method of claim 1 , wherein said substrate comprises a crystalline defect solid that provides oxygen to a reaction.