Abstract:

(CeMn)_1-xZr_xO₂ catalysts were prepared by co-precipitation, where 0≤x≤0.3 and the molar ratio of CeO₂ to MnO₂ was 6: 4. The catalytic activities of these catalysts for the catalytic combustion of diesel soot were investigated. The catalysts were further characterized by a series of characterization methods. The results of X-ray diffraction(XRD) and low temperature nitrogen adsorption-desorption measurements indicated that the addition of ZrO₂ improved the structure properties and textural properties of aged catalysts. When x≥0.2, the catalysts exhibited optimum structure properties, while improved textural properties could be observed for the catalysts with x≥0.1. The results of H₂-temperature programmed reduction(H₂-TPR) measurements revealed that, among the ZrO₂-doped aged catalysts, the one with x=0.2 exhibited the best low-temperature reduction ability. The results of O₂-temperature programmed desorption(O₂-TPD) measurements suggested that the adding of ZrO₂ increased the anion vacant sites on the surface of the catalysts and improved the catalyst's ability to adsorb and activate O₂. The results of catalytic activities of these catalysts discolsed that T_m(T_m is the temperature at which the maximal mass loss can be observed in the combustion process of soot) of the fresh catalysts decreased by about 270 ℃. After aged, the adding of ZrO₂ increased the stability. When x=0.2, the catalyst exhibited excellent thermal resistance performance, the gap of T_m before and after aging was only 6 ℃. These catalysts suggested potential application in diesel soot catalytic combustion.

Key words: Zirconium content, Soot, Catalytic combustion, Aging resistance