Efficient Catalysts of K and Ce Co-Doped LaMnO3 for NO x -Soot Simultaneous Removal and Reaction Kinetics.

Presently, the treatment of four-way catalysts is important for reducing pollutant emissions from diesel engine exhaust, which is a major cause of urban haze. In this study, we prepared perovskite-type catalysts via the citric acid sol-gel method. Experiment results showed that K substitution at site A in LaMnO3 decreased the agglomeration of the catalysts effectively, increased the contact with the reaction gas, promoted the conversion of Mn3+ → Mn4+, and reduced the ignition temperature of soot. Ce substitution at the B-site in La0.5K0.5MnO3 produced a CeO2 phase and decreased the Mn4+/Mn3+ ratio to 0.49, which is conducive to improving the catalytic oxidation performance. The K and Ce co-doping had the best activation effect, which showed a low activation energy (10.87 KJ mol-1) and a high simultaneous removal rate of NO x (reaching 90% at 275 °C) and soot ignition at 250 °C under lean conditions.