Activity of Rh{sup x+} species in CO oxidation and NO reduction in a CO/NO/O{sub 2} stoichiometric mixture over a Rh/CeO{sub 2}-ZrO{sub 2} catalyst

Journal Article · Sun Oct 25 00:00:00 EDT 1998 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1998.2222· OSTI ID:289440

Fajardie, F; Blanchard, G ^[1]; Tempere, J F; Manoli, J M; Djega-Mariadassou, G ^[2]; Touret, O ^[3]

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1. Rhone Poulenc, Aubervilliers (France). Centre de Recherches d`Aubervilliers
2. Univ. P and M Curie, Paris (France). Lab. de Reactivite de Surface
3. Rhone Poulenc, La Rochelle (France)

The catalytic activity of a 0.30 wt% Rh/CeO{sub 2}-ZrO{sub 2} catalyst (25% ZrO{sub 2} in weight) 188 m{sup 2}/g was studied in the oxidation of CO and reduction of NO in a CO/NO/O{sub 2} stoichiometric mixture, in the temperature range of 298--773 K. The hydrogenation of benzene, a structure insensitive reaction was used for counting surface Rh(0) atoms after either thermal treatment of the catalyst in hydrogen at 773 K, or reduction by the stoichiometric CO/O{sub 2}/NO reaction mixture. The bibliography shows that the turnover rate over RH{sup x+} is lower than that over Rh(0) by two orders of magnitude. Rhodium supported on CeO{sub 2}-ZrO{sub 2} submitted to the above reducing treatments was found to be totally inactive in benzene hydrogenation but active in CO/NO/O{sub 2} reaction. As a conclusion the present catalyst consisted exclusively of Rh{sup x+} surface species. The catalyst behavior of this rhodium-supported catalyst was interpreted in terms of multiple active sites containing one Rh{sup x+} ion grafted in the support and able to chemisorb CO and/or NO as for a rhodium homogeneous complex. This Rh{sup x+} is associated with two adjacent oxygen vacancies (and corresponding Ce{sup 3+} cations) linked to the reduction of the support and permitting oxygen and NO chemisorption. A method was defined for counting surface Rh{sup x+} containing multiple sites by measuring the number of NO molecules adsorbed at low temperature and desorbing at the temperature of light-off of CO. A (NO/Rh{sup x+}) ratio of 2 was found, in agreement with a dinitrosyl species reaction intermediate.

• OSTI ID: 289440
• Journal Information: Journal of Catalysis, Vol. 179, Issue 2; Other Information: PBD: 25 Oct 1998
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
33 ADVANCED PROPULSION SYSTEMS
CARBON MONOXIDE
OXIDATION
NITRIC OXIDE
SELECTIVE CATALYTIC REDUCTION
RHODIUM
CERIUM OXIDES
ZIRCONIUM OXIDES
CATALYTIC EFFECTS
AIR POLLUTION CONTROL