The Importance of Soot-Catalyst Contact to Regeneration of Catalytic Diesel Particulate Filters

Catalytic (i.e., catalyst-coated) diesel particulate filters (DPFs) represent the best option for removing particulate matter, which is mostly composed of soot, from diesel engine exhaust. This work is focused on the main critical issue for regeneration of catalytic DPFs: the contact in the solid-solid reaction between soot and catalyst. Both experimental and numerical results show that, in order to fully exploit the potential of catalytic DPFs in soot abatement, both a widespread and homogeneous presence of catalyst in the macro-pores of the filter walls and a suitably low soot load are needed. Under optimal soot-catalyst contact conditions, the consequent decrease in the temperature required for soot oxidation to values within the temperature range of diesel exhausts suggests the passage to a continuous functioning mode for catalytic filters with simultaneous filtration and regeneration. This functioning mode enables overcoming the drawbacks of periodic regeneration performed in current applications, including the formation of excessively hot regions that may severely damage the DPF.