Promotional Effect of Hydroxyl on the Aqueous Phase Oxidation of Carbon Monoxide and Glycerol over Supported Au Catalysts
Gold particles supported on carbon and titania were explored as catalysts for oxidation of CO or glycerol by O{sub 2} at room temperature in liquid-phase water. Although Au/carbon catalysts were not active for vapor phase CO oxidation at room temperature, a turnover frequency of 5 s{sup -1} could be achieved with comparable CO concentration in aqueous solution containing 1 M NaOH. The turnover frequency on Au/carbon was a strong function of pH, decreasing by about a factor of 50 when the pH decreased from 14 to 0.3. Evidently, a catalytic oxidation route that was not available in the vapor phase is enabled by operation in the liquid water at high pH. Since Au/titania is active for vapor phase CO oxidation, the role of water, and therefore hydroxyl concentration, is not as significant as that for Au/carbon. Hydrogen peroxide is also produced during CO oxidation over Au in liquid water and increasing the hydroxyl concentration enhances its formation rate. For glycerol oxidation to glyceric acid (C{sub 3}) and glycolic acid (C{sub 2}) with O{sub 2} (1-10 atm) at 308-333 K over supported Au particles, high pH is required for catalysis to occur. Similar to CO oxidation in liquid water, H{sub 2}O{sub 2} is also produced during glycerol oxidation at high pH. The formation of the C-C cleavage product glycolic acid is attributed to peroxide in the reaction.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 930432
- Report Number(s):
- BNL-81176-2008-JA; TRN: US200904%%540
- Journal Information:
- Topics in Catalysis, Vol. 44, Issue 39449; ISSN 1022-5528
- Country of Publication:
- United States
- Language:
- English
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