Alkali/alkaline-earth metal-modified MnO supported on three-dimensionally ordered macroporous-mesoporous TiSiO catalysts: Preparation and catalytic performance for soot combustion.

The performance of catalysts used in after-treatment systems is the key factor for the removal of diesel soot, which is an important component of atmospheric fine particle emissions. Herein, three-dimensionally ordered macroporous-mesoporous TiSiO (3DOM-m TiSiO) and its supported MnO catalysts doped with different alkali/alkaline-earth metals (AMnO/3DOM-m TiSiO (A: Li, Na, K, Ru, Cs, Mg, Ca, Sr, Ba)) were prepared by mesoporous template (P123)-assisted colloidal crystal template (CCT) and incipient wetness impregnation methods, respectively. Physicochemical characterizations of the catalysts were performed using scanning electron microscopy, X-ray diffraction, N adsorption-desorption, H temperature-programmed reduction, O temperature-programmed desorption, NO temperature-programmed oxidation, and Raman spectroscopy techniques; then, we evaluated their catalytic performances for the removal of diesel soot particles. The results show that the 3DOM-m TiSiO supports exhibited a well-defined 3DOM-m nanostructure, and AMnO nanoparticles with 10-50 nm were evenly dispersed on the inner walls of the uniform macropores. In addition, the as-prepared catalysts exhibited good catalytic performance for soot combustion. Among the prepared catalysts, CsMnO/3DOM-m TiSiO had the highest catalytic activity for soot combustion, with T, T, and T (the temperatures corresponding to soot conversion rates of 10%, 50%, and 90%) values of 285, 355, and 393°C, respectively. The high catalytic activity of the CsMnO/3DOM-m TiSiO catalysts was attributed to their excellent low-temperature reducibility and homogeneous macroporous-mesoporous structure, as well as to the synergistic effects between Cs and Mn species and between CsMnO and the TiSiO support.