Thermal stability of MnO_x-CeO2 mixed oxide for soot combustion: influence of Al2O3, TiO2, and ZrO2 carriers

摘要

MnO_x-CeO2 (Mn/Ce =0.15/0.85)mixed oxidematerials supported on ZrO2,Al2O3, and TiO2 were prepared by citrate sol-gelmethod to prevent the CeO2-based oxide catalyst fromsintering during soot combustion reaction. The materials were characterized using XRD, BET method, HRTEM, H2-TPR, and XPS. Results indicate that the MnO_x-CeO2/TiO2 catalyst is rapidly sintered at 800 ° C because of the TiO2 phase change from anatase to rutile. By contrast, MnO_x-CeO2 catalysts supported on Al2O3 and ZrO2 show high thermal stability. After aging at 800 ° C for 10 h, the MnO_x-CeO2 crystalline structure remained highly dispersed on the carrier. Particularly with the ZrO2 carrier, the amount of surface oxygen species and redox properties of MnO_x-CeO2 can be well-maintained for the synergistic effect of CeO2 and ZrO2 in high temperature environments. Good agreement is found between the low-temperature redox property (200 ° C to 400 ° C) and the soot combustion activity of the catalysts.