Effect of Catalyst Coating Strategy on NOx Reduction and Passive Soot Oxidation for Selective Catalytic Oxidation-Selective Catalytic Reduction Catalyst on Diesel Particulate Filter

Selective catalytic oxidation/reduction catalysts coated on diesel particulate filters (SDPF) are an important technology route to meet next-stage emission regulations. The previous research of the research group showed that compared with SDPF coated with Cu-SSZ-13, the SDPF coated with novel selective catalytic oxidation-selective catalytic reduction (SCO-SCR) catalyst, which combined MnO₂-CeO₂/Al₂O₃ and Cu-SSZ-13, can simultaneously improve NOx reduction and soot oxidation performance. Catalyst coating strategy is an important parameter affecting the performance of SDPF. In this study, the effects of different coating strategies of SCO-SCR catalysts (C25, C50, C75, and C100) on the performance of NOx reduction and soot oxidation in SDPF were investigated. The results show that, as the inlet gas temperature increases, NO emissions first decrease and then increase, NOx conversion efficiency first increases and then decreases, and the rich-NO₂ area, NH₃ oxidation rate, N₂O, CO, CO₂ emissions, and pressure drop increase. By expanding the catalyst coating area, the NH₃ oxidation rate, NOx conversion efficiency, NO₂, N₂O, CO, CO₂ emission and pressure drop of filter wall all increased, the pressure drop of soot cake layer and NO emissions decreased. When the temperature is 450 °C, there are rich-NO₂ areas at both the front end and rear end of C100. The 25% area at the rear end of the filter wall coated with SCO-SCR catalyst can increase NOx conversion efficiency and soot regeneration efficiency. While the impact on N₂O generation is small. Still, it will lead to excessive NO₂ emissions. The increased magnitude in NOx conversion efficiency and soot regeneration efficiency decease as the catalyst coating area expands.