Passive Soot Oxidation Improvement in an SCR Coated DPF Through Adding an Additional SCO Catalyst

Ben  Jensen, Pacific Northwest National Laboratory

Increased thermal efficiency and more stringent emissions regulations on today’s diesel engines has necessitated the need for better cold start performance of diesel exhaust aftertreatment systems. A promising solution for better cold start NOx reduction is a selective catalytic reduction (SCR) catalyst coated diesel exhaust filter (SDPF). The SDPF can be placed closer to the engine than in a traditional DPF-SCR system enabling better cold start SCR functionality. One drawback of an SDPF is the negative impact on passive soot regeneration in the filter due to the reduction of NO2. This issue is particularly impactful to the Heavy-Duty market, which relies heavily on passive soot regeneration.

 

This research looks to improve passive soot regeneration while maintaining the SCR capabilities of the SDPF. The main objective is to increase NO2 concentrations in the SDPF filter to enable increased NO2 soot reactions for passive soot regeneration conditions while minimizing adverse impact on SCR performance. A strategy to improve NO2 soot reactions is to generate NO2 insitu by introducing a selective catalytic oxidation (SCO) catalyst together with the SCR catalyst coating on the DPF. The performance of different SCR and SCO washcoat loading strategies will be evaluated using computer simulation software Exothermia Suite and experimental tests on mini core filters. The performance with regards to reduction of NOx and passive soot regeneration of these different catalyst loading strategies will be presented.