Model-based optimization of catalyst zoning on SCR-coated particulate filters

- Zone-coated filters with SCR function are numerically benchmarked.
- Wall-flow selectivity resulting from catalyst zoning governs filter performance.
- Distributing the coating near the rear of the filter shows improvement potential.

The integration of selective catalytic reduction (SCR) and diesel particulate filter (DPF) into a single device (so called SCRF® or SDPF) can decrease the packaging volume and costs in modern diesel exhaust aftertreatment systems. While SDPF has already found its way into commercial application in passenger cars, for heavy-duty and non-road applications additional aspects need to be considered. Since these systems typically rely on NO2-assisted regeneration for the removal of soot, the interactions between the SCR and DPF functionalities become important and influence the SDPF performance. Within this frame, advanced coating techniques are investigated in order to limit the detrimental effect of these cross-interactions and achieve optimal system design and control. This study focuses on the evaluation of non-uniform wall impregnation in the axial direction, referred to as catalyst zoning. A validated SDPF mathematical model, able to quantitatively predict the SCR/DPF interactions, is used. The performance of the zone-coated filters is evaluated under both steady-state and transient conditions while the observed phenomena and underlying mechanisms are analytically discussed.