Kinetics of the selective low-temperature oxidation of CO in H{sub 2}-rich gas over Au/{alpha}-Fe{sub 2}O{sub 3}
- Univ. Ulm (Germany). Abteilung Oberflaechenchemie und Katalyse
The selective CO oxidation (also referred to as PROX) on a Au/{alpha}-Fe{sub 2}O{sub 3} catalyst in simulated reformer gas (low concentrations of CO and O{sub 2}, 75 kPa H{sub 2}, balance N{sub 2}) at atmospheric pressure was investigated over almost two orders of magnitude in CO partial pressure (0.025--1.5 kPa) and over a large range of p{sub O{sub 2}}/p{sub CO} ratios (0.25--10). Quantitative evaluation of CO oxidation rates as a function of CO and O{sub 2} partial pressure at 80 C yields reaction orders with respect to CO and O{sub 2} of 0.55 and 0.27, respectively. The apparent activation energy for this reaction evaluated in the temperature range of 40--100 C is 31 kJ/mol. At 80 C, the selectivity, defined as the ratio of oxygen consumption for CO oxidation to the total oxygen consumption, reaches 75% at large CO partial pressures (1.5 kPa), but decreases significantly with diminishing p{sub CO}. This is related to the fact that the H{sub 2} oxidation rate is independent of the CO partial pressure, consistent with a reaction mechanism where oxygen adsorbed at the metal/metal oxide interface reacts with H and CO adsorbed at low coverages on the supported Au nanoclusters. The selectivity increases with decreasing temperature, reflecting a higher apparent activation energy for H{sub 2} oxidation than for Co oxidation. A comparison with Pt/{gamma}-Al{sub 2}O{sub 3}, a commonly used PROX catalyst with an optimum operating temperature of ca. 200 C, demonstrates that Au/{alpha}-Fe{sub 2}O{sub 3} already offers comparable activity and selectivity at 80 C.
- OSTI ID:
- 338554
- Journal Information:
- Journal of Catalysis, Vol. 182, Issue 2; Other Information: PBD: 10 Mar 1999
- Country of Publication:
- United States
- Language:
- English
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