Al2O3-CeO2 Oxides: Synthesis, Characterization and Evaluation as Catalytic Supports in Benzene Combustion. Surface Ceria Effects

Abstract

Abstract Al2O3-CeO2 sol-gel oxides were obtained at ceria loadings of 2, 5, 10, 20 and 50 wt.%, calcined at 700 °C and characterized by N2 physisorption, XRD, TEM, 27Al MAS-NMR, and TPR. All samples present high amounts of surface ceria species and bulk ceria has significant presence from 20 wt.% of ceria. The sample with 50 wt.% presents both the reduction of bulk and interfacial ceria species and X-ray diffraction peaks corresponding to cerianite phase. Surface ceria dispersion degree (surface ceria/total reduced ceria) was determined to be 100 % for samples with 2 and 5 wt.% CeO2, with a slight decrease to ca. 90 % and 75 % for samples with 10 and 20 wt.% CeO2 respectively, and a lower value of 41 % for the sample with 50 wt.% CeO2. It was found the amount of surface ceria has a good correlation with the amount of AlV sites, indicating that incorporated Ce ions distorts the alumina matrix and restricts the amount of surface ceria. Platinum supported on these materials showed that the catalytic activity in benzene combustion for oxygen-depleted environments increased as the surface ceria concentration increased.