INFLUENCE OF MUTUAL PLATINUM-DISPERSED CERIA INTERACTIONS ON THE PROMOTING EFFECT OF CERIA FOR THE CO OXIDATION REACTION IN A PT CEO2/AL2O3CATALYST/

Catalytic activity tests in combination with characterization studies (using CO temperature programmed reduction, electron paramagnetic reso nance, and Fourier transform infrared) have been performed with the ai m of establishing which are the main factors influencing the reactivit y of an oxidized Pt/CeO2/Al2O3 catalyst for the CO-O-2 reaction. Sever al effects are induced by the presence of both platinum and dispersed ceria in the catalyst. The results show that the low-temperature reduc ibility of both platinum and dispersed ceria is enhanced when the two components are present in the catalyst. Analysis of the characteristic s of the centers responsible of the latter effect, carried out by mean s of EPR using oxygen as the probe molecule, indicates that in this sa mple the most reducible sites are formed by platinum located on bidime nsional ceria patches present at the alumina surface. The enhancement by ceria of the low-temperature reduction of platinum at these sites u nder a CO + O-2 reacting mixture, observed even when starting from oxi dized catalysts, leads us to propose these sites as highly active for the CO oxidation reaction.