Influence of Ceria Dispersion on the Catalytic Performance of Cu/(CeO_2)/Al_2O_3 Catalysts for the CO oxidation Reaction.

摘要

Cu/CeO_2/Al_2O_3 catalysts containing different amounts of ceria, as well as Cu/Al_2O_3 and Cu/CeO_2 samples, have been studied in thermal programmed CO oxidation experiments, and characterized with EPR and FTIR. The presence of copper-ceria contacts is revealed by analysis of superoxide-EPR spectra in a Cu/CeO_2/Al_2O_3 samples. These interactions stabilize copper in a reduced state, as indicated by the formation of carbonyls giving bands at 2106-2098 cm~(-1) in the FTIR spectra of CO adsorbed on the calcined samples. On the basis of the reactivity profiles obtained it is proposed that copper-ceria contacts largely promote catalytic reactivity, enhancing the formation of active reduced Cu species, and that the heterogeneity of the different supports, where tridimensional ceria entities appear (together with bidimensional patches) as the ceria loading is increased, leads to the presence of different copper entities whose properties change as a function of their interactions witht he different parts of the support; the final catalytic activity seems to be higher for Cu species interacting with 3-D ceria than for those contacting more dispersed 2-D ceria entities.