Evaluation of an Integrated Selective Catalytic Reduction-Coated Particulate Filter

In this study, an SCR-coated particulate filter with soot loaded from engine bench experiments was evaluated. Prior to soot loading, the sample was hydro-thermally aged at 850 °C. Flow reactor measurements were performed under various reaction conditions to examine the impact of soot in an SCR-coated diesel particulate filter (DPF) on standard SCR, fast SCR, NH 3 oxidation, and NO oxidation. In the presence of soot, NO x conversion was slightly lower at 200–300 °C due to the blocking of active sites. However, at higher temperatures, the NO x conversion was somewhat higher with soot, indicating that soot more strongly inhibited the oxidation of NH 3 than the SCR reaction. When feeding equal amounts of NO and NO 2 together with NH 3, ammonium nitrates on the sample were formed. The presence of soot significantly decreased the formation or the stability of ammonium nitrate, resulting in higher conversion with soot. To further understand this interesting aspect, ammonium nitrate formation and decomposition experiments using model Cu/BEA catalyst with and without soot were performed. It was observed that less N 2 O was formed in the presence of soot, and this in combination with CO x formation during the ammonium nitrate formation step suggested that soot reacted with the ammonium nitrates, and we propose that this occurs on CuO species on the outside of the zeolite particles.