Effect of A-site substitution on the simultaneous catalytic removal of NOx and soot by LaMnO3 perovskites

Abstract

The simultaneous catalytic removal of NO_x and soot by La_1−xM_xMnO₃ (M = K, Sr, Pr; x = 0, 0.1, 0.2, 0.3) perovskites was investigated. The properties of the catalysts were characterized by XRD, FT-IR, BET, SEM, XPS, H₂-TPR and soot-TPR. The results showed that K⁺, Sr²⁺ and Pr³⁺ successfully entered the lattice and formed a perovskite structure. The catalyst doped with K⁺ exhibited the most outstanding performance. The La_0.8K_0.2MnO₃ catalyst showed the best catalytic activity with 39.07% NO conversion and 92.41% N₂ selectivity; the soot burning rates reached 10% (T_i) and 50% (T_m) at 365 °C and 420 °C, respectively. More oxygen vacancies and Mn⁴⁺ ions appeared in the catalyst with the increase in K⁺, due to which the ratio of O_ads/O_lat and Mn⁴⁺/Mn³⁺ changed regularly; this increased the ability of removing NO_x and diesel soot particles.