LNT/CDPF catalysts for simultaneous removal of NOx and PM from diesel vehicle exhaust

• NOx conversion of LNT(2Pt20Ba)/CDPF combined with LNT and CDPF was 49% at 370 °C.
• NOx conversion of the LNT(2Pt20Ba5Co)/CDPF was improved to 55% at 310 °C.
• LOT50 of the particulate matter was 550 °C over the LNT/CDPF.
• The rate of PM oxidation over the LNT/CDPF was higher than one over the bare DPF.

The objective of the present study is to investigate the simultaneous removal characteristics of NOx and PM over LNT/CDPF which the combination of an lean NOx trap (LNT) catalyst and a diesel particulate filter (DPF). LNT catalysts were prepared by an impregnation method, and then analyzed through TEM, BET surface area, and EDS to investigate their physical characteristics. It was found from experiments with the LNT catalysts that the NOx conversion of 2Pt20Ba/Al2O3 coated with cordierite substrate was 65% at 350 °C, which demonstrated the highest de-NOx performance among other LNT catalysts. The NOx conversion of LNT(2Pt20Ba)/CDPF combined with LNT and CDPF was 49% at 370 °C. When 5 wt% cobalt was added to 2Pt20Ba/Al2O3 catalyst to improve the NOx conversion of the LNT/CDPF, the NOx conversion of the LNT(2Pt20Ba5Co)/CDPF was improved to 55% at 310 °C. The initiation temperature for PM oxidation was 250 °C, and LOT50 of the PM was 550 °C over the LNT/CDPF. In particular, the rate of PM oxidation over the LNT/CDPF was higher than one over the bare DPF, which was not coated with LNT catalyst.

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