The dynamics of oxygen exchange with zirconia-supported PdO
- Univ. of California, Berkeley, CA (United States). Dept. of Chemical Engineering
- Lawrence Berkeley National Lab., CA (United States)
Isotopic tracer methods involving {sup 18}O and {sup 16}O were used to investigate the dynamics of O{sub 2} adsorption and desorption from the surface of zirconia-supported PdO and the dynamics of O atom diffusion through the bulk of PdO. The rate coefficient for the recombination of O atoms is found to be 1.4 {times} 10{sup 13} exp({minus}144,000/RT) s{sup {minus}1} and the diffusivity of O atoms through bulk PdO is 1.6 {times} 10{sup {minus}10} exp({minus}89,000/RT) cm{sup 2}/s. In both cases, the activation energies are in units of kJ/mol. While oxygen exchange with pure ZrO{sub 2} was not observed under the conditions of the present experiments, such exchange did occur to a limited degree when PdO was supported on ZrO{sub 2}, the degree of exchange increasing with decreasing PdO particle size. Palladium oxide supported on zirconia is known to be a particularly active catalyst for the combustion of methane. Analysis of the reaction kinetics suggests that dissociatively adsorbed CH{sub 4} reacts with oxygen atoms present at the surface of PdO particles. The oxygen lost from the catalyst is replenished by dissociative adsorption of O{sub 2} from the gas phase and by diffusion from the catalyst bulk. For this reason it is of interest to measure the dynamics of oxygen adsorption and desorption, as well as the dynamics of oxygen diffusion through bulk PdO.
- Sponsoring Organization:
- Petroleum Research Fund (United States); USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 684576
- Journal Information:
- Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 185; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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