Evaluation of the effect of substrate structure on the passive soot oxidation and NOx reduction of DPF coated with SCO-SCR catalyst

The application of selective catalytic reduction/oxidation (SCR/SCO) catalysts onto diesel particulate filters (DPF) constitutes a critical strategy for meeting stringent emission regulations. Compared to conventional Cu-SSZ-13 coated on DPF, the novel SCO-SCR integrated DPF (n-SDPF) demonstrates dual functionality in enhancing simultaneous soot combustion and NOx abatement. In this study, a multiphysics model couples factors such as fluid dynamics, mass transfer, chemical reaction and heat transfer was established to assess the impact of substrate structure on soot oxidation and NOx reduction of n-SDPF. Key findings reveal that, SCR catalytic pathways exhibit preferential activation over NH₃ oxidation processes. Enhanced filter wall thickness and extended filter wall length proportionally increase active site density, whereas optimized inlet-to-outlet channel width ratios promote gas-phase reactant charge. When the filter wall thickness increased from 0.25 mm to 0.4 mm, the maximum NOx conversion efficiency increased from 74.76 % to 86.39 %, and the maximum soot oxidation efficiency increased from 15.03 % to 15.83 %. When the filter wall length increased from 140 mm to 200 mm, the NOx conversion efficiency increased from 78.45 % to 88.41 %, and the soot oxidation efficiency increased from 14.62 % to 18.28 %. When the inlet-to-outlet channel width ratio increased from 1 to 1.6, the NOx conversion efficiency decreased from 91.01 % to 77.85 %, and the soot oxidation efficiency decreased from 20.04 % to 14.41 %. Filter wall length extension demonstrates superior technical advantages, achieving improvement in NOx conversion efficiency and enhancement in soot oxidation rates while concurrently reducing pressure drop across both soot cake layers and filter walls. In this study, the coupling relationship between catalytic reaction and substrate structure is revealed. The findings will provide theoretical support for n-SDPF design and practical applications.