Hierarchical Porous K-OMS-2/3DOM-m Ti0.7Si0.3O2 Catalysts for Soot Combustion: Easy Preparation, High Catalytic Activity, and Good Resistance to H2O and SO2

Soot particles are recognized as one of the main sources of air pollution; therefore, it is an urgent need to eliminate them from the air effectively. Catalytic combustion is a promising strategy for soot abatement, yet the development of highly efficient catalysts is still an important challenge for practical applications. In this study, novel hierarchical porous K-OMS-2/3DOM-m Ti0.7Si0.3O2 catalysts, in which the Ti0.7Si0.3O2 supports contain ordered macropores and mesopores and the K-OMS-2 active phase contains micropores, were purposefully designed and successfully prepared using a simple method. The macropores and mesopores in the as-prepared catalysts were formed by PMMA and P123 as templates, and the micropores were brought about by K-OMS-2, a specific crystal form of cryptomelane. The K-OMS-2/3DOM-m Ti0.7Si0.3O2 catalysts exhibit high catalytic activity for soot combustion, along with high stability and good resistance to sulfur and water. Among the synthesized catalysts, K-OMS-2/3DOM-m Ti0.7Si0.3O2-450 shows the highest catalytic activity with T10, T50, and T90 values of 288, 333, and 364 °C, respectively. This catalyst also exhibits good stability after five catalytic cycles with T10, T50, and T90 values in the range of 290 ± 4, 335 ± 4, and 368 ± 4 °C, respectively. The excellent catalytic performance in soot combustion associated with high NO oxidation activity is attributed to the hierarchical pore effect, a synergistic effect between K and Mn, as well as to doping with Ti. Molecular density functional theory (DFT) and thermodynamic modeling indicated that both Langmuir–Hinshelwood and Eley–Rideal mechanisms may operate in the NO to NO2 oxidation on the K-OSM-2 surface, yet the former is energetically slightly more preferred. Because of their easy synthesis, low cost, high activity, good stability, and good resistance to sulfur and water, the developed optimal K-OMS-2/3DOM-m Ti0.7Si0.3O2 catalysts are promising for practical applications in soot combustion filters.