Perovskite-Based Lean-Burn NOx Trap Catalysts Without Using Platinum Group Metals: K/LaCoO3/Ce1−xZrxO2

A series of Ce1-xZrxO2 (x = 0, 0.1, 0.2, 0.3) solid solution supported lean-burn NOx trap (LNT) catalysts K/LaCoO3/Ce1-xZrxO2 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 NOx storage and sulfurresisting performance of the catalysts, the optimal atomic ratio of Zr in Ce1-xZrxO2 support is x = 0.2. The catalyst K/LaCoO3/Ce0.8Zr0.2O2 exhibits much better NOx storage capacity than the Pt-based catalyst Pt/K/Ce0.8Zr0.2O2, which is highly related to its stronger capability for NO to NO2 oxidation. During NOx 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/LaCoO3/Ce1-xZrxO2, 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.