Influence of catalyst coating on pore characteristics, catalytic activity and backpressure of catalyzed diesel particulate filters: in-wall vs. on-wall

Abstract

The catalyzed diesel particulate filter (CDPF) has been a standard approach for diesel engines to reduce soot emissions. In this study, the interface morphology, pore structure, soot oxidation and flow characteristics of the CDPF with in-wall and on-wall coating were comparatively investigated. The results showed that the pore volume, porosity, and average pore diameter of the in-wall coating CDPF are lower than those of the on-wall coating CDPF. An increase in catalyst loading will reduce the pore volume, porosity, and average pore diameter of the CDPF, with a more significant impact on the in-wall coating CDPF. The characteristic pore diameter parameters, D₁₀ and D₉₀ (the pore diameters corresponding to 10% and 90% of the total pore volume, respectively), of the in-wall coating CDPF are smaller than those of the on-wall coating CDPF. When the catalyst loading is 3 g L⁻¹, the D₁₀ values of the in-wall coating CDPF and the on-wall coating CDPF are 2.5 μm and 2.7 μm, respectively, and the D₉₀ values are 9.1 μm and 9.6 μm, respectively. As the catalyst loading increases, the soot oxidation activity of the CDPF gradually increases, and the soot oxidation ignition temperature and activation energy show a downward trend. The soot oxidation activity of the in-wall coating CDPF is superior to that of the on-wall coating CDPF, with the lowest activation energies being 96 kJ mol⁻¹ and 102 kJ mol⁻¹, respectively. The backpressure of the on-wall coating CDPF is significantly lower than that of the in-wall coating CDPF, with a greater decrease in backpressure during the deep bed capture stage and filter cake capture stage. This study provides an important reference for optimizing the catalyst coating process of a CDPF to improve its performance.