Performance of K and Ni substituted La1−xKxCo1−yNiyO3−δ perovskite catalysts used for soot combustion, NOx storage and simultaneous NOx-soot removal

The nanometric substituted perovskite catalysts La1−xKxCo1−yNiyO3−δ (x = 0, 0.1; y = 0, 0.05, 0.1) were synthesized by citric acid complexation method, and employed for soot combustion, NOx storage and simultaneous NOx-soot removal. Their structures and physico-chemical properties were characterized by XRD, EXAFS, BET, SEM, H2-TPR, and XPS techniques. When K and Ni are simultaneously introduced into LaCoO3 catalyst, soot combustion is largely accelerated, with the temperature (Tm) for maximal soot conversion lowered by at least 50 °C; moreover, NOx reduction by soot is also facilitated. The La0.9K0.1Co0.95Ni0.05O3−δ catalyst exhibits not only the lowest Tm (367 °C) temperature but also the highest soot combustion rate (67.3 μg/s g catalyst). Meanwhile, the NOx reduction percentage over this catalyst can reach 21%. The kinetic results show that the activation energy for soot combustion over La0.9K0.1Co0.95Ni0.05O3−δ (81.34 kJ mol−1) is much lower than that over LaCoO3 (107.7 kJ mol−1). The H2-TPR and XPS results show that the La0.9K0.1Co0.95Ni0.05O3−δ catalyst possesses better redox properties, more tetravalent cobalt ions and larger amount of surface adsorbed oxygen species, which determines its novel performance for soot combustion, NOx storage and soot-NOx removal.