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 selected from the group consisting of titanias, zirconias, silicas, zeolites, and montmorillonites wherein (a) the molar ratio of platinum to gold of the catalyst composition is from about 4:1 to 1:1 and (b) the gold-platinum alloy is formed at a temperature between about 200° C. and about 350° C.
2. The catalyst composition of claim 1 , wherein the particles of gold-platinum alloy and particles consisting essentially of platinum (0) constitute less than or equal to about 10 wt % of the catalyst composition.
3. The catalyst composition of claim 1 , wherein the particles of gold-platinum alloy and particles consisting essentially of platinum (0) constitute from about 1 wt % to about 8 wt % of the catalyst composition.
4. The catalyst composition of claim 1 , wherein the particles of gold-platinum alloy and particles consisting essentially of platinum (0) constitute from about 1 wt % to about 4 wt % of the catalyst composition.
5. The catalyst composition of claim 1 , wherein the particles of gold-platinum alloy and particles consisting essentially of platinum (0) are present in a molar ratio of platinum to gold from about 2:1 to 1:1.
6. The catalyst composition of claim 2 , wherein the particles of gold-platinum alloy and particles consisting essentially of platinum (0) are present in a molar ratio of platinum to gold from about 2:1 to 1:1.
7. The catalyst composition of claim 1 , wherein the support comprises zirconia.
8. The catalyst composition of claim 1 , wherein the support is selected from the group consisting of titanias, zirconias and silicas.
9. The catalyst composition of claim 1 , wherein the support comprises titania.
10. The catalyst composition of claim 1 , further comprising a Group 6 metal.
11. The catalyst composition of claim 1 , further comprising a Group 10 metal in addition to platinum.
12. The catalyst composition of claim 1 , wherein at least about 50% of the gold-platinum alloy particles have a particle size that is less than or equal to about 20 nanometers.
13. The catalyst composition of claim 12 , wherein at least about 50% of the gold-platinum alloy particles have a particle size in the range of about 2 to about 15 nm.
14. The catalyst composition of claim 13 , wherein at least about 50% of the gold-platinum alloy particles have a particle size in the range of about 5 to about 12 nm.
15. The catalyst composition of claim 1 , wherein at least about 50% of the particles consisting essentially of platinum (0) have a particle size that is less than or equal to about 50 nanometers.
16. The catalyst composition of claim 15 , wherein at least about 50% of the particles consisting essentially of platinum (0) have a particle size in the range from about 2 to about 50 nanometers.
17. A mixture comprising glucose in contact with a catalyst composition, wherein the catalyst composition comprises particles of gold-platinum alloy and particles consisting essentially of platinum (0) on a support selected from the group consisting of titanias, zirconias, silicas, zeolites, and montmorillonites wherein (a) the molar ratio of platinum to gold of the catalyst composition is from about 4:1 to 1:1 and (b) the gold-platinum alloy is formed at a temperature between 200 C and about 350 C.
18. The mixture of claim 17 , wherein the support comprises titania.
19. The mixture of claim 17 , further comprising a solvent comprising water.
20. The mixture of claim 17 , further comprising oxygen.