Simulation on catalytic reaction in diesel particulate filter

Abstract

To reduce particulate matters (PM) in diesel exhaust gas, stricter exhaust emission standards such as Euro V are being set in many countries. Recently, for the after-treatment of exhaust gas, a diesel particulate filter (DPF) has been developed. Latest researches have shown that DPF filtration efficiency can be as high as 99%. However, the filter would be plugged with particles to cause an increase of filter back-pressure, which must be kept at lower levels, because the higher back-pressure increases fuel consumption and reduces available torque. Here, we are focusing on NO x -soot conversion system. There are two stages for PM oxidation. At the first step, the catalyst oxidizes NO in exhaust gas into NO 2. At the next step, NO 2 reacts with soot to produce CO and CO 2. However, the reaction rate and quantitative effect of NO 2 on soot oxidation is not clear, because it is difficult to observe small-scale phenomena in DPF experimentally, and there is not enough information on the PM oxidation. In this study, we simulated the above two-stage system. In the first part, the reaction with Pt catalyst for the oxidation of NO to NO 2 was simulated in non-porous flow-through filter. The catalytic reaction mechanism was discussed. In the second part, we simulated the flow in wall-flow filter to confirm the effectiveness of regeneration process by NO 2 in the real cordierite DPF.