Ordered macro-mesoporous nanostructure of Pd/ZrO2 catalyst for boosting catalytic NO-assisted soot oxidation

Abstract

Herein, the hierarchical porous catalysts of three dimensional ordered macro-mesoporous (3DOMM) ZrO2-supported active Pd nanoparticles (NPs) were prepared by two-step methods of evaporation-induced self-assembly-colloid crystal template (EISA-CCT) and gas bubbling-assisted membrane reduction (GBMR). Ordered macroporous structure can enhance diffusion and mass transfer of soot particles; ordered mesoporous structure is beneficial to enhance activation ability for gaseous reactants. Synergistic effect of hierarchical porous structure in the catalysts is important to improve catalytic activity for soot oxidation. Pd/3DOMM-ZrO2 catalyst exhibits the highest activity (T50 = 404 °C) for soot oxidation compared with the single macroporous or mesoporous structure. The catalytic kinetics of hierarchical porous Pd/3DOMM-ZrO2 catalyst for soot oxidation was systemically investigated, i.e., its reaction rate is 0.038 μmol g-1 s−1 at 310 °C, which is 2.7-fold of power-type Pd/normal-ZrO2 catalyst (0.014 μmol g-1 s−1). The hierarchical porous structure is a good strategy to boost catalytic activity during soot oxidation.