Oxidation catalysts
Disclosed are catalysts comprised of platinum and gold. The catalysts are generally useful for the selective oxidation of compositions comprised of a primary alcohol group and at least one secondary alcohol group wherein at least the primary alcohol group is converted to a carboxyl group. More particularly, the catalysts are supported catalysts including particles comprising gold and particles comprising platinum, wherein the molar ratio of platinum to gold is in the range of about 100:1 to about 1:4, the platinum is essentially present as Pt(0) and the platinum-containing particles are of a size in the range of about 2 to about 50 nm. Also disclosed are methods for the oxidative chemocatalytic conversion of carbohydrates to carboxylic acids or derivatives thereof. Additionally, methods are disclosed for the selective oxidation of glucose to glucaric acid or derivatives thereof using catalysts comprising platinum and gold. Further, methods are disclosed for the production of such catalysts.
1. A catalyst composition comprising particles of gold-platinum alloy and particles consisting essentially of platinum (0) on a support comprising titania wherein (a) the molar ratio of platinum to gold of the catalyst is from about 4:1 to 1:1, (b) the particle sizes of the platinum (0) particles are substantially in the range of from about 2 to about 50 nanometers, (c) the total gold and platinum metal loading of the catalyst is from about 2 to about 8 wt %, and (d) the gold-platinum alloy is formed at a temperature between about 200° C. and about 350° C. and wherein the catalyst has the ability to catalyze conversion of glucose to glucaric acid at a yield in excess of 60%.
2. The catalyst composition of claim 1 wherein the total gold and platinum metal loading of the catalyst is from about 2 to about 4 wt %.
3. The catalyst composition of claim 2 wherein the molar ratio of platinum to gold of the catalyst is from about 3:1 to 1:1.
4. The catalyst composition of claim 2 wherein the molar ratio of platinum to gold of the catalyst is from about 2:1 to 1:1.
5. The catalyst composition of claim 1 wherein the particles sizes of the particles consisting essentially of platinum (0) are substantially in the range of from about 5 to about 20 nanometers.
6. The catalyst composition of claim 1 wherein the particle sizes of the gold-platinum alloy particles are substantially in the range of from about 2 to about 20 nanometers.
7. The catalyst composition of claim 6 wherein at least about 50% of the gold-platinum alloy particles have a size from about 5 to about 12 nanometers.
8. The catalyst composition of claim 6 wherein the total gold and platinum metal loading of the catalyst is from about 2 to about 4 wt %.
9. The catalyst composition of claim 8 wherein the molar ratio of platinum to gold of the catalyst is from about 3:1 to 1:1.
10. The catalyst composition of claim 8 wherein the molar ratio of platinum to gold of the catalyst is from about 2:1 to 1:1.
11. The catalyst composition of claim 1 wherein at least about 50% of the particles consisting essentially of platinum (0) have a size from about 8 to about 12 nanometers.
12. The catalyst composition of claim 1 wherein the molar ratio of platinum to gold of the catalyst is from about 3:1 to 1:1.
13. The catalyst composition of claim 1 wherein the molar ratio of platinum to gold of the catalyst is from about 2:1 to 1:1.
14. The catalyst composition of claim 1 further comprising metal selected from Group 6 metals.
15. The catalyst composition of claim 1 further comprising a Group 10 metal in addition to platinum.
16. A process for preparing glucaric acid or derivatives thereof comprising reacting glucose with a source of oxygen in the presence of the catalyst of claim 1 .
17. The process of claim 16 wherein the particle sizes of the gold-platinum alloy particles are substantially in the range of from about 2 to about 20 nanometers.
18. The process of claim 17 wherein the total gold and platinum metal loading of the catalyst is from about 2 to about 4 wt %.
19. The process of claim 16 wherein the total gold and platinum metal loading of the catalyst is from about2 to about 4 wt %.
20. The process of claim 16 wherein the catalyst further comprises a metal selected from Group 6 metals.
21. The process of claim 16 wherein the catalyst further comprises a Group 10 metal in addition to platinum.
22. The process of claim 16 wherein the catalyst further comprises wherein the molar ratio of platinum to gold of the catalyst is from about 2:1 to 1:1.