Efficient catalytic removal of diesel soot over Mg substituted K/La_0.8Ce_0.2CoO₃ perovskites with large surface areas

Mg-substituted La_0.8Ce_0.2CoO₃ (LCCM) perovskite oxides with large surface areas (148.7 m²/g) were prepared by a modified citric acid complexation method. Then, K promoted LCCM catalysts were synthesized via impregnation. The samples were characterized by XRD, FT-IR, N₂ adsorption-desorption, SEM, TEM, XPS and TG/DTA techniques. The addition of Mg not only restrained the growth of LCCM crystallite, but also inhibited the agglomeration of nanoparticles and, consequently the surface areas of LCCM perovskites increased. The low-valence ion substitution of Mg²⁺ both promoted the formation of Co⁴⁺ and adsorbed oxygen species, which were further enhanced by the partial replacement of La³⁺ by K⁺. The local electron density of neighboring carbon sites and their affinity for binding oxygen atom were promoted by K promotion, which also contributed to the contact between soot and catalyst surface, and the activity of the catalyst was thus enhanced. Among all the catalysts, the K/LCCM-4 calcined at 600 °C exhibited the highest activity with T_m,t at 380 °C, and maintained good stability with T_m,l only increased by 10 °C after recycling for three times.