Impacts of catalyst coating on the filtration performance of catalyzed wall-flow filters: From the viewpoint of microstructure

Initial filtration efficiency and soot loading characteristics are important performance criteria for catalyzed wall-flow filters. In this context, the influence of catalyst coating on filtration performance was investigated over a set of bare and coated silicon carbide (SiC) filter cores. Catalyst coating demonstrates a significant decrease effect on the initial filtration efficiency. Both filtration efficiency and pressure drop increase faster with time on coated filters in the deep-bed filtration regime. The scanning electron microscopy (SEM) results reveal that catalyst is preferentially deposited in the smaller pores. The mercury intrusion porosimetry (MIP) data show that catalyst coating reduces the pore volume for the pores relevant to filtration. The capillary flow porometry (CFP) results confirm that the coated catalyst wipes out a group of smaller pores. Accordingly, for the first time, we provide a working mechanism to explain the decreased filtration efficiency on catalyzed filters based on the experimental results and characterization data.