Effects of cerium incorporation on the catalytic oxidation of benzene over flame-made perovskite La1-xCexMnO3 catalysts
摘要
Perovskite-type La1-xCexMnO3（x = 0-10%） catalysts were prepared by flame spray pyrolysis and their activities during the catalytic oxidation of benzene were examined over the temperature range of100-450℃.The structural properties and reducibility of these materials were also characterized by X-ray diffraction（XRD）,N2 adsorption/desorption,H2 temperature-programmed reduction（H2-TPR） and X-ray photoelectron spectroscopy（XPS）.The incorporation of Ce was found to improve the benzene oxidation activity,and the perovskite in which x was 0.1 exhibited the highest activity.Phase composition and surface elemental analyses indicated that non-stoichiometric compounds were present.The incorporation of Ce had a negligible effect on the specific surface area of the perovskites and hence this factor has little impact on the catalytic activity.Introduction of Ce44+ resulted in modification of the chemical states of both B-site ions and oxygen species and facilitated the reducibility of the perovskite.The surface Mn4+/Mn3+ratio was increased as a result of Ce4+ substitution,while a decrease in the surface-adsorbed O/lattice O(Oads/Olatt) ratio was observed.The relationship between the surface elemental ratios and catalytic activity was established to allow a better understanding of the process by which benzene is oxidized over perovskites.