Experimental and theoretical study on La0.5K0.5Mn1−xFexO3 perovskite catalysts for mild temperature soot combustion and simultaneous removal of soot and NO

Abstract

In order to control high emissions of soot and NOx from diesel engines, this research utilizes highly efficient perovskite oxide catalysts to simultaneously remove soot and NO. A series of La0.5K0.5Mn1-xFexO3 catalysts were prepared by citric acid complexation method, and the active sites and structure stability of LaMnO3 perovskite catalyst were investigated according to the first principle. Research results show that K+ doping causes the transformation of Mn3+ into Mn4+ in LaMnO3 catalyst system and forms more oxygen vacancies. Meanwhile, Fe3+ doping leads to the octahedron distortion of MnO6 and FeO6 in catalyst system, which enhances the stability of catalyst structure. The oxygen vacancy formed by doping K+ and Fe3+ accelerates the migration rate of lattice oxygen and improves the catalytic activity of perovskite catalyst for soot oxidation. With the increase of Fe3+ doping, the proportion of adsorbed oxygen and high valence active ions in catalyst system increases. Moreover, the alkaline sites on the catalyst surface are favorable for the adsorption of acid gas NO. The La0.5K0.5Mn0.67Fe0.33O3 catalyst has the highest catalytic activity, the ignition temperature of soot oxidation drops to 291 °C, and CO2 selectivity exceeds 99.9%. At 370 °C, the conversion rate of NO reaches the maximum value of 61.7%.