Study Of Superficial Active Oxygen On CuO-CeO₂ Complex Oxides Catalyst Towards Purification Of Soot Carbon In Exhaust Gas From Diesel-fuelled Vehicles

Soot particles in exhaust gas from diesel-fuelled vehicles have caused a serious environmental pollution, thus promoting the establishment of more emission standards. CuO-CeO2 was found to accelerate soot combustion under low temperature. The catalytic performance was guaranteed mainly due to its active oxygen species. Therefore, this paper studied the effects of solvent used in the preparation process on active oxygen species.In this paper, catalysts CuO-CeO2-A and CuO-CeO2-W were prepared using the method of citrate acid complex-combustion, and absolute alcohol and water were used as the solvents for comparsion, respectively. Characterization techniques were used, including temperature programmed oxidation (TPO), and characterized by temperature programmed reduction (H2-TPR), temperature programmed desorption (O2-TPD), x-ray diffraction (XRD), Fourier transform infrared spectrophotometer (FTIR), and x-ray photoelectron spectroscopy(XPS).The effect of different solvents on surface active oxygen species as one of activity factors was inverstigated. The main results are as follows:(1) The same crystal structure was found in CuO-CeO2-A and CuO-CeO2-W, prepared by citrate acid complex-combustion with absolute alcohol or water as solvents. And both of the catalysts exhibited the formation of solid solution.(2) Absolute alcohol could enhance the distribution of CuO on surface of CeO2 and increases the amount ofβoxygen, which favors the oxidation of CO, not soot. For soot oxidation, the main active oxygen species is a oxygen, but notβoxygen.(3) Solvent affects the catalytic activity mainly via changing the distribution of CuO and oxygen storage capacity of catalyst.(4) CuO-CeO2-A prepared by citrate acid complex-combustion using absolute alcohol as the solvent keep the cubic fluorite structure as CeO2 until n(Ce)/(n(Ce)+n(Cu)<20%, and then CuO in crystal phase is formed.(5) Without NOx and SO2 in act system, the amount of lattice oxygen has no effect on catalytic activity for CuO-CeO2 prepared by citrate acid complex-combustion with absolute alcohol or water as solvents to catalytic combustion of soot.