KNO₃ supported on three-dimensionally ordered macroporous La_0.8Ce_0.2Mn_{1-: X}Fe_xO₃ for soot removal

Three-dimensionally ordered macroporous (3DOM) La_0.8Ce_0.2Mn_1-xFe_xO₃ perovskites were successfully prepared by a colloidal crystal template method and KNO₃-supported 3DOM La_0.8Ce_0.2Mn_1-xFe_xO₃ catalysts were prepared by a wetness impregnation method. Physicochemical properties of these catalysts were characterized by XRD, FT-IR, FESEM, TEM, BET, H₂-TPR, O₂-TPD, and XPS techniques and their catalytic performances were evaluated by soot combustion. All these perovskites possessed a well-ordered 3DOM structure, and KNO₃ was highly dispersed on the skeleton of the supporters without changing the morphology and crystal structure of the perovskites. The 3DOM structure provides an increased contact area between the catalyst and soot. Besides, partial replacement of Mn by Fe into the perovskites increased the surface area and reducibility. The introduction of K ions increased the amount of active oxygen species in the catalysts, which could accelerate soot combustion at low temperature. On the other hand, the NO₃^- species brought by KNO₃ were beneficial to the reaction at high temperature. Among all the samples, the 3DOM K/La_0.8Ce_0.2Mn_0.6Fe_0.4O₃ exhibited the highest catalytic performance with the lowest T₅₀ at 379 °C.