REACTIVITY OF PTAL2O3 AND PT-CEO2AL2O3 CATALYSTS FOR THE OXIDATION OF CARBON-MONOXIDE BY OXYGEN .1. CATALYST CHARACTERIZATION BY TPR USING CO AS REDUCING AGENT

Ceria, platinum, and platinum-ceria catalysts supported on α-alumina have been characterized by temperature-programmed reduction (TPR) using CO as reducing agent. In all cases, CO disproportionation was found to be negligible. Nevertheless, a small CO2 TPR signal was detected on the α-alumina support at tempratures higher than 673 K, and has been attributed to the water-gas shift reaction between gaseous CO and the hydroxyl groups of the alumina surface. The comparison between the CO-TPR spectra of CeO2/Al2O3 and Pt-CeO2/Al2O3 has revealed that platinum induces a downscale shift on the temperature of the ceria reduction peak. Two possible interpretations of this platinum-ceria interaction are proposed: (i) a CO bond weakening when CO is adsorbed on platinum particles and (ii) a decrease of the CeO bond strength for ceria localized near platinum. © 1993 Academic Press, Inc.