Soot oxidation over CeO2-ZrO2 based catalysts: The influence of external surface and low-temperature reducibility

Fresh CeO2-ZrO2-Y2O3-La2O3 (CZYL) catalyst was synthesized via calcining at 600 degrees C of relative precipitates obtained by co-precipitation and then aged at 700-1000 degrees C. Afterwards, 10wt% MnO2 was further loaded on the fresh and 800 degrees C-aging sample, respectively. The oxidation activity tests illustrate that the catalytic performance of CZYL catalysts firstly remains stable and then decreases with increasing aging temperature. Systematical investigations suggest that the amount of surface oxygen vacancies and O-2 desorption ability of all these CeriaZirconia (CZ) based catalysts may be high enough to make little difference on their catalytic activity. On the contrary, it is found that the external surface area and low-temperature reducibility (< 500 degrees C) are the two major factors to influence the soot oxidation activity. Interestingly, the external surface area will does no difference when its value is above a critical point. Furthermore, only relatively larger distinction in low-temperature reducibility among catalysts will contribute to apparently various catalytic activity.