Method of producing multi-component catalysts
Supported catalysts are produced with nanometer sized particles comprised of different metals dispersed throughout the catalyst support material. The supported catalysts reduce substantially or completely the amount of platinum that is required without sacrificing catalytic performance. In place of platinum, the supported catalysts employ palladium, silver, or copper, all of which costs significantly less than platinum.
1. A method of producing a supported platinum-palladium catalyst, comprising the steps of:
contacting a quantity of alumina support material with a volume of water for a first time period to form a liquid mixture, wherein said volume of water is greater than two times a pore volume of said quantity of alumina support material;
adding a platinum salt solution having a molar concentration of 0.0001 to 0.1 and a palladium salt solution having a molar concentration of 0.0001 to 0.1 to said liquid mixture following said first time period and stirring said liquid mixture for a second time period;
adding a reducing agent to said liquid mixture following said second time period and stirring said liquid mixture for a third time period;
separating out said quantity of alumina support material with platinum particles and palladium particles supported thereon from the liquid mixture; and
drying said quantity of alumina support material with platinum particles and palladium particles supported thereon,
wherein said platinum salt is reduced to platinum particles within said liquid mixture during said third time period, and said palladium salt is reduced to palladium particles within pores of said quantity of alumina support material within said liquid mixture during said third time period.
2. The method according to claim 1 , wherein said platinum salt solution added to said liquid mixture comprises dissolved platinum ions and said palladium salt solution added to said liquid mixture comprises dissolved palladium ions.
3. The method according to claim 2 , wherein pH of said liquid mixture is not adjusted after the platinum salt solution and the palladium salt solution are added to said liquid mixture.
4. The method according to claim 3 , wherein said reducing agent is chosen from the group consisting of N 2 H 4 , NH 2 OH, sodium citrate, potassium citrate, ammonium citrate, alkali metal borohydrides, alcohols and glycols.
5. The method according to claim 4 , wherein the reducing agent comprises NH 2 OH.
6. The method according to claim 4 , wherein said platinum salt solution comprises Pt(NO 3 ) 2 and the palladium salt solution comprises Pd(NH 3 ) 4 (NO 3 ) 2 .
7. The method according to claim 4 , wherein the combined metal weight loading of the platinum and palladium metal particles is less than 1%.
8. The method according to claim 1 , wherein the platinum to palladium weight loading ratio is between 3:1 to 4:1.
9. A method of producing a supported mixed metal catalyst, comprising the steps of:
contacting a quantity of support material with a volume of solvent for a first time period to form a liquid mixture, wherein said volume of solvent is greater than two times a pore volume of said quantity of support material;
adding a metal salt solution of a first type having a molar concentration of 0.0001 to 0.1 to said liquid mixture following said first time period and stirring said liquid mixture for a second time period;
adding a first reducing agent to said liquid mixture following said second time period and stirring said liquid mixture for a third time period, wherein said metal salt of the first type is reduced to metal particles within pores of said quantity of support material within said liquid mixture during said third time period;
adding a metal salt solution of a second type having a molar concentration of 0.0001 to 0.1 to said liquid mixture following said third time period and stirring said liquid mixture for a fourth time period; and
adding a second reducing agent to said liquid mixture following said fourth time period and stirring said liquid mixture for a fifth time period, wherein said metal salt of the second type is reduced to metal particles within pores of said quantity of support material within said liquid mixture during said fifth time period.
10. The method according to claim 9 , wherein said metal salt solution of the first type added to said liquid mixture comprises dissolved metal ions of the first type and said metal salt solution of the second type added to said liquid mixture comprises dissolved metal ions of the second type.
11. The method according to claim 10 , wherein pH of said liquid mixture is not adjusted from start of the first time period until end of the fifth time period.
12. The method according to claim 11 , wherein one of the two types of metals is platinum.
13. The method according to claim 12 , wherein both of said first and second reducing agents are chosen from the group consisting of N 2 H 4 , NH 2 OH, sodium citrate, potassium citrate, ammonium citrate, alkali metal borohydrides, alcohols and glycols.
14. The method according to claim 13 , wherein both of said first and second reducing agents comprise NH 2 OH.
15. The method according to claim 14 , wherein the first reducing agent is different from the second reducing agent.
16. The method according to claim 13 , wherein the platinum salt comprises Pt(NO 3 ) 2 .
17. The method according to claim 12 , wherein the weight loading of the platinum particles is less than 1%.
18. The method according to claim 12 , wherein one of the two types of metals is silver or copper.
19. The method according to claim 9 , wherein the support material comprises alumina and the solvent is water.