Laboratory Study of Soot, Propylene, and Diesel Fuel Impact on Zeolite-Based SCR Filter Catalysts

Selective Catalytic Reduction (SCR) catalysts have been designed to reduce NOx with the assistance of an ammonia-based reductant. Diesel Particulate Filters (DPF) have been designed to trap and eventually oxidize particulate matter (PM). Combining the SCR function within the wall of a high porosity particulate filter substrate has the potential to reduce the overall complexity of the aftertreatment system while maintaining the required NOx and PM performance. The concept, termed Selective Catalytic Reduction Filter (SCRF) was studied using a synthetic gas bench to determine the NOx conversion robustness from soot, coke, and hydrocarbon deposition. Soot deposition, coke derived from propylene exposure, and coke derived from diesel fuel exposure negatively affected the NOx conversion. The type of soot and/or coke responsible for the inhibited NOx conversion did not contribute to the SCRF backpressure. Reaction gas exposure at 450°C completely regained the NOx conversion without regenerating the soot and without gaining backpressure relief. Similarly to the soot-loaded experiments, coke generated from propylene exposure negatively affected NOx conversion for both Cu/zeolite SCRF formulations studied. However, coke generated from diesel fuel vapor impacted one Cu/zeolite SCRF catalyst formulation but not the other.