Effect of a novel catalyst zonal coating strategy on the performance of SCR coated particulate filters

Abstract

The selective catalytic reduction catalysts (SCR) coated into a diesel particulate filter (DPF), so called SDPF, can reduce both NOx and particulate in the exhaust gas of diesel engines, which is a promising technology to meet stringent emission regulations. Advanced coating techniques are crucial for optimizing SDPF technology, and this study focused on the effect of a novel catalyst zonal coating strategy on the performance of SDPFs. Three SDPF samples with 50 %, 75 %, and 100 % catalyst coating (named samples I, II, and III, respectively) were tested at ten steady-state engine operating conditions. The results showed that catalyst zonal coated SDPFs (samples I and II) had good NOx conversion rates under most conditions, but the NOx conversion rates of both samples dropped below 80 % at 2200 r/min with full engine load condition. The three SDPF samples had similar pressure drops at low exhaust flow, while catalyst zonal coated SDPFs showed lower pressure drops and flow resistance at high engine speed and heavy engine load conditions, especially for sample I. Catalyst zonal coated SDPFs had slightly lower particulate filtration efficiencies than that of sample III, because some small particulates with a diameter of<50 nm could escape from the catalyst uncoated area due to its high porosity.