Highly efficient multifunctional dually-substituted perovskite catalysts La_(1-x)K_xCo_(1-y)Cu_yO_(3-δ)used for soot combustion, NOx storage and simultaneous NOx-soot removal

摘要

A series of K/Cu simultaneously substituted nanometric perovskite catalysts La_(1-x)K_xCo_(1-y)Cu_yO_(3-δ) (x=0, 0.1; y = 0, 0.05, 0.1, 0.2, 0.3) were synthesized by citric acid complexation, which were employed for soot combustion, NOx storage and simultaneous NOx-soot removal. The physico-chemical properties of the catalysts were characterized by XRD, FT-IR, EXAFS, SEM, H2-TPR, Soot-TPR, TG/DTA, XPS and in situ DRIFTS techniques. When K and Cu are simultaneously introduced into LaCoO3, soot combustion is largely accelerated, decreasing the characteristic temperature (T_m) corresponding to the maximal soot combustion rate at least 80 °C; moreover, NOx reduction by soot is also remarkably facilitated. Among all the catalysts La_(0.9)K_(0.1)Co_(0.9)Cu_(0.1)O_(3-δ) shows the lowest T_m of 360°C, the highest NOx storage capacity (NSC) of 284u,molg~' and the largest NOx reduction percentage of 32%; for soot combustion, it also exhibits the lowest activation energy (80.04 kJ mol~(-1)). The XPS and Soot-TPR results reveal that the catalyst La_(0.9)K_(0.1)Co_(0.9)Cu_(0.1)O_(3-δ) possesses more active and larger amount of surface oxygen species (02~ and 0~), more tetravalent cobalt ions and better reducibility than others, which determines its better catalytic performance. Based on in situ DRIFTS and other characterization results, the potential mechanisms for soot combustion, NOx storage and simultaneous NOx-soot removal are proposed.