Promotion of Oxidation and Reduction of Rh Species by Interaction of Rh and CeO₂ over Rh/CeO₂/SiO₂

Oxidation and reduction of Rh species on Rh/CeO₂/SiO₂ catalyst were promoted by the presence of CeO₂ as indicated from the comparison of the profiles of the temperature-programmed oxidation (TPO) and reduction (TPR) of Rh/CeO₂/SiO₂ and Rh/SiO₂. In situ quick scanning X-ray absorption fine structure (QXAFS) during the TPO and TPR indicates that the formation of the Rh−O−Ce bond was followed by that of Rh−O−Rh during the TPO, and that the Rh−O−Ce bond dissociated more easily than the Rh−O−Rh bond during the TPR. These behaviors can explain the promoting effect of CeO₂ on the oxidation and reduction of Rh species on Rh/CeO₂/SiO₂. In addition, it is found that the addition of CeO₂ to Rh/SiO₂ enhanced the catalytic activity in the partial oxidation of tar from cellulose pyrolysis in the fluidized bed reactor and in the combustion of the methane. The promoting effect of CeO₂ on the catalytic performance is related to the interaction between Rh species and CeO₂.