Comparative study on redox properties and catalytic behavior for CO oxidation of CuO/CeO2 and CuO/ZrCeO4 catalysts

Redox processes occurring during the CO-O-2 reaction and catalytic properti es for CO oxidation have been examined for CuO/CeO2 and CuO/ZrCeO4 catalyst s using catalytic activity tests, in situ DRIFTS and EPR spectroscopies, an d CO-TPD. EPR results suggest synergetic effects in the reduction-oxidation of these systems, both copper and the support being involved in these redo x processes. Both EPR and CO-TPD experiments indicate a more facile reducti on by CO of the CuO/CeO2 system, mainly due to the greater reducibility of sites at the interface between the copper oxide clusters and the support fo r this catalyst. A greater CO oxidation activity is exhibited by the CuO/Ce O2 catalyst. A comparison of both catalysts and analysis of the redox prope rties of the different copper entities present in the catalysts indicate th at the active copper sites for CO oxidation are located on the copper oxide clusters. On the basis of the results obtained by the different techniques , it is proposed that CO oxidation in these systems follows a redox mechani sm in which both the support and copper oxide clusters are simultaneously r educed or oxidized following interaction with CO or O-2, respectively. The limiting step in the reaction is related to the oxidation process. (C) 2000 Academic Press.