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

MnOx-CeO2 (Mn/Ce = 0.15/0.85) mixed oxide materials supported on ZrO2, Al2O3, and TiO2 were prepared by citrate sol-gel method to prevent the CeO2-based oxide catalyst from sintering during soot combustion reaction. The materials were characterized using XRD, BET method, HRTEM, H-2-TPR, and XPS. Results indicate that the MnOx-CeO2/TiO2 catalyst is rapidly sintered at 800 degrees C because of the TiO2 phase change from anatase to rutile. By contrast, MnOx-CeO2 catalysts supported on Al2O3 and ZrO2 show high thermal stability. After aging at 800 degrees C for 10 h, the MnOx-CeO2 crystalline structure remained highly dispersed on the carrier. Particularly with the ZrO2 carrier, the amount of surface oxygen species and redox properties of MnOx-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 degrees C to 400 degrees C) and the soot combustion activity of the catalysts.