Catalytic oxidation of soot particulates over MnO_x-CeO_2 oxides prepared by complexation-combustion

MnO_x-CeO_2 oxides prepared by complexation-combustion method were used for soot oxidation.The highest conversion rate of soot was obtained on a MnO_x-CeO_2 oxide prepared under mild acid condition of pH=4,where the oxidation temperature corresponding to maximum activity was decreased more than 150℃ compared with that of un-catalytic soot oxidation.The structure and property of the catalysts were investigated by X-ray powder diffraction(XRD)and temperature programmed reduction(TPR).The results indicated that there were at least two kinds of Mn species present in MnO_x-CeO_2 catalysts,i.e.Mn ions within CeO_2 lattice and high dispersion MnO_x on the surface of CeO_2.The presence of Mn ions in the CeO_2 lattice improved the oxygen vacancy due to the charge difference,and the CeO_2 considerably decreased the reduction temperature of MnO_x.The capability to activate oxygen through the oxygen exchange between O_2 in gas phase and lattice oxygen species in MnO_x-CeO_2 oxide contributed to the high catalytic activity for the reaction.