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.