Perovskite-Based Lean-Burn NO_x Trap Catalysts Without Using Platinum Group Metals: K/LaCoO3/Ce_(1-x)Zr_xO2

摘要

A series of Ce_(1-x)Zr_xO2 (x = 0, 0.1, 0.2, 0.3) solid solution supported lean-burn NO_x trap (LNT) catalysts K/LaCoO3/Ce_(1-x)Zr_xO2 were prepared by successive impregnation. After sulfation the supported perovsikte LaCoO3 was well maintained; reducing treatment partly destroyed the perovsikte, but it can be well recovered by re-oxidation treatment. Based on NO_x storage and sulfur-resisting performance of the catalysts, the optimal atomic ratio of Zr in Ce_(1-x)Zr_xO2 support is x = 0.2. The catalyst K/LaCoO3/Ce_(0.8)Zr_(0.2)O2 exhibits much better NO_x storage capacity than the Pt-based catalyst Pt/K7Ce_(0.8)Zr_(0.2)O2, which is highly related to its stronger capability for NO to NO2 oxidation. During NO_x storage much larger amounts of nitrate and nitrite species were identified by in situ DRIFTS over perovskite-based catalysts than over Pt-based one. The H2-TPR results reveal that after deep sulfation little sulfur species were deposited on the catalyst K/La-CoO3/Ce_(1-x)Zr_xO2, showing strong sulfur-resisting ability. As a result, it is thought that the full replacement of Pt by perovskite LaCoO3 in the corresponding LNT catalysts is feasible.