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 T-10, T-50, and T-90 values of 288, 333, and 364 degrees C, respectively. This catalyst also exhibits good stability after five catalytic cycles with T-10, T-50, and T-90 values in the range of 290 +/- 4, 335 +/- 4, and 368 +/- 4 degrees 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.

Automated summary

Soot particles are a major source of air pollution, and catalytic combustion is an effective strategy for reducing them. The study successfully developed novel catalysts with high catalytic activity and stability.