Alkali/alkaline-earth metal-modified MnO supported on three-dimensionally ordered macroporous–mesoporous Ti Si1-O2 catalysts: Preparation and catalytic performance for soot combustion

• AMnO x /3DOM-m Ti 0.7 Si 0.3 O 2 (A: alkali/alkaline-earth metals) catalysts were successfully synthesized by simple method. • The as-prepared catalysts have three-dimensionally ordered macroporous–mesoporous structure and excellent redox properties. • CsMnO x /3DOM-m Ti 0.7 Si 0.3 O 2 catalyst exhibits high catalytic activity and good stability 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 Ti x Si 1- x O 2 (3DOM-m Ti x Si 1- x O 2 ) and its supported MnO x catalysts doped with different alkali/alkaline-earth metals (AMnO x /3DOM-m Ti 0.7 Si 0.3 O 2 (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 2 adsorption–desorption, H 2 temperature-programmed reduction, O 2 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 Ti 0.7 Si 0.3 O 2 supports exhibited a well-defined 3DOM-m nanostructure, and AMnO x 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 x /3DOM-m Ti 0.7 Si 0.3 O 2 had the highest catalytic activity for soot combustion, with T 10 , T 50 , and T 90 (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 x /3DOM-m Ti 0.7 Si 0.3 O 2 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 x and the Ti 0.7 Si 0.3 O 2 support.