Investigation of Soot Oxidation Carried out on Membrane Filters Composed of SiC Nanoparticles

The diesel particulate membrane filter (DPMF) is a good solution to the problem of high pressure drop that exists across diesel particulate filters (DPFs) as a result of the soot trapping process. Moreover, DPMFs that have a membrane layer composed of SiC nanoparticles can reduce the oxidation temperature of soot and the apparent activation energy. The SiC nanoparticles have an oxide layer on their surface, with a thickness less than 10 nm. From the visualization of soot oxidation on the surface of SiC nanoparticles by an environmental transmission electron microscope (ETEM), soot oxidation is seen to occur at the interface between the soot and oxide layers. The soot oxidation temperature dependency of the contact area between soot and SiC nanoparticles was evaluated using a temperature programmed reactor (TPR). The contact area between soot and SiC nanoparticles was varied by changing the ratio of SiC nanoparticles and carbon black (CB), which was used as an alternative to soot. If the contact area between CB and SiC nanoparticles was large enough, CB oxidation temperatures were almost the same whether Pt was embedded in the oxide layer or not. Furthermore, the CB oxidation temperature was found to depend on the oxygen concentration in the gas phase. Pt helped increase the amount of adsorbed oxygen on the surface of SiC nanoparticles.