A kinetic and adsorption study of CO oxidation over unsupported fine gold powder and over gold supported on titanium dioxide
The catalytic oxidation of CO with O{sub 2} and adsorption of CO{sub 2} and O{sub 2} on Au deposited on TiO{sub 2} (AuTiO{sub 2}, mean diameter of gold particles 3.5 nm), TiO{sub 2}, and unsupported Au powder (mean diameter 76 nm) have been investigated by using a closed recirculation reaction system. The catalytic oxidation of CO with O{sub 2} on Au/TiO{sub 2} measured at 253--293 K proceeded very rapidly. In the same temperature range, fine gold powder was catalytically active, while TiO{sub 2} alone was entirely inactive for the oxidation. The rate constant of CO oxidation per unit of surface area of gold was larger by two orders of magnitude for Au/TiO{sub 2} than for Au powder. Adsorption of CO and CO{sub 2} occurred almost instantaneously and reversibly on preoxidized Au/TiO{sub 2}, whereas a slow increase in the O{sub 2} pressure was observed at 273 K in the absence of evacuation. A similar increase of O{sub 2} pressure was observed from oxidized TiO{sub 2}, but Au powder did not show any increase. The increase was ascribed to the desorption of weakly adsorbed O{sub 2} on the support surface of Au/TiO{sub 2}. The rate of reduction of preoxidized Au/TiO{sub 2} with CO almost corresponded to the increase in the O{sub 2} pressure and was far smaller than the rate of the catalytic oxidation of CO with O{sub 2} on the catalyst, indicating that molecular oxygen weakly adsorbed on the support surface of Au/TiO{sub 2} contributes only partly to the catalytic oxidation of CO. During the oxidation, O{sub 2} in the gas phase may be directly activated on the surface of deposited gold particles and/or on the very narrow perimeter interface between the gold and the support.
- Research Organization:
- Kyoto Inst. of Tech., Sakyo (JP)
- OSTI ID:
- 20000958
- Journal Information:
- Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 187; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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