Effects of hydrothermal aging on SiC-DPF with metal oxide ash and alkali metals

The silicon carbide used to make diesel particulate filters (SiC-DPF) has a maximum temperature of use, which is not the melting point of the filter material itself but rather the eutectic melting points of the ash materials and alkali metals deposited on the filter wall. Chemical reactions between the SiC filter and the other materials, i.e. ash materials and/or alkali metals, decrease the filtration efficiency and catalytic reactivity of engine out emission. The objective of this study is to understand the effect of hydrothermal aging on the SiC-DPF, and on the SiC-CDPF (catalyzed diesel particulate filter) deposited with ash materials and/or alkali metals. Hydrothermal aging simulated for the extreme condition of uncontrolled regeneration in DPF is carried out by using H2O at high temperature. The surface change of the SiC filter was characterized in terms of the geometric microstructure and metal composites of the filter by using the SEM-EDS, BET and XRD. The accumulated ash materials and alkali metals in the SiC-DPF were an admixture, and the SiC-DPF after-treatment system always contained H2O. According to the results, H2O in the after-treatment system can be regarded as an influential factor of SiC-DPF durability even though the SiC itself has a very high melting point. The regeneration temperature has to be controlled under a critical value to ensure the durability of SiC-DPF in the after-treatment system, considering the fact that large quantities of ash materials, alkali metals and H2O components are included in the exhaust gas.