Factors affecting the catalytic performance of la-k-mn-o perovskite oxides for diesel soot oxidation

Soot combustion performance of K-containing perovskite oxides, La_0.8K_0.2MnO₃ (LKM82), was evaluated under tight- and loose-contact conditions. The perovskite oxides were prepared by evaporation-to-dryness methods using malic acid or citric acid as the complexing reagents. Catalyst surface area, surface K concentration, and morphology of the LKM82 catalysts can be controlled by changing the preparation conditions. The temperature of soot combustion decreased with increasing catalyst surface area and surface K concentration of the LKM82 catalysts, indicating that these are important factors controlling the soot combustion performance. The increase in surface area and surface K concentration of the LKM82 catalysts improved soot ignition activity and promoted the soot combustion reaction after ignition. In the loose-contact mode, the ratio of the amount of catalytically combusted soot to that of non-catalytically combusted soot increased with an increase in catalyst surface area and surface K concentration of the LKM82 catalysts. The apparent activation energy of the catalytic soot combustion with the perovskite oxides that have both high surface area and high surface K concentration was much lower than that of non-catalytic soot combustion.