The catalytic behavior of La-Mn-O nanoparticle perovskite-type oxide catalysts for the combustion of the soot particle from the diesel engine

The La_1−xM_x MnO₃(M=Li, Na, K, Rb, x=0, 0.10, 0.25) perovskite-type oxides whose sizes are nanoparticle have been prepared by the citric acid-ligated method. The characters of the catalysts were characterized by means of XRD, IR, SEM and BET surface area measurement. The catalytic activity for the combustion of soot particulate was evaluated by a technique of the temperature-programmed reaction. In the LaMnO₃ catalyst, the partial substitution of alkali metal (Li, Na, K, Rb) into A-site enhanced the catalytic activity for the combustion of soot particle. The La_0.75K_0.25MnO₃ oxides are good candidate catalysts for the soot particle removal reaction, and the combustion temperatures of soot particle are between 285 °C and 430 °C when the contact of catalysts and soot is loose, and their catalytic activities for the combustion of soot particle are as good as supported Pt catalysts, which is the best catalyst system so far reported for soot combustion under loose contact conditions.