Understanding the effects of catalytic partial flow filters on particle removal efficiency

The combination of filtration and catalytic pollutant's removal within one aftertreatment component is investigated in this work. A catalytic partial flow filter as a particulate oxidation catalyst (POC) has been chosen for this study. The trapping and oxidation functions as well as its close-coupled position, which provides higher exhaust temperature profiles, can promote passive regeneration as a mean to limit the build-up of soot in the filter. This component is not intended as a replacement of the diesel particulate filter (DPF) in the exhaust system, but it can help reducing the frequency and/or duration of the DPF active regeneration, thus limiting the impact on fuel economy and CO2 emissions. The pollutant's oxidation activity, particulate filtration mechanisms and effect on particulate matter characteristics of the POC have been comprehensively researched under a wide range of engine operation conditions, varying by particle concentration, space velocity and temperature. The interactions between the DPF and the POC have been studied from the filtration and backpressure point of view. Long term filtration and catalytic performance as well as passive regeneration have been also studied. Results show that combining oxidation and filtration functions within a single unit helps to achieve greater catalytic pollutant removal capability and a significant particulate matter filtration efficiency, reducing the pressure increase across the DPF.