Lanthanum-promoted copper-based hydrotalcites derived mixed oxides for NOx adsorption, soot combustion and simultaneous NOx-soot removal

•The addition of La in Cu-based oxides increased the types of active oxygen.•NOx adsorption, soot oxidation and simultaneous NOx-soot removal were enhanced.•The possible catalytic mechanism was studied via in situ FTIR analysis.•Soot oxidation was promoted by the NO2 intermediate.

La-promoted Cu-based hydrotalcites derived mixed oxides were prepared and their catalytic activities for NOx adsorption, soot oxidation, and simultaneous NOx-soot removal were investigated. The catalysts were characterized by XRD, DTG, BET, FTIR, H2-TPR, TPD and TPO techniques. The oxides catalysts exhibited mesoporous properties with specific surface area of 45–160 m2/g. The incorporation of La and Cu decreased the amount of basic sites due to the large decrease in surface areas. Under O2 atmosphere, La incorporation is dominant for soot oxidation activity, while Cu favors high selectivity to CO2 formation. A synergetic effect between La and Cu for catalyzed soot oxidation lies in the improved redox property and suitable basicity. The presence of NO in O2 significantly promoted soot oxidation on the catalysts with the ignition temperature decreased to about 300 °C. In O2/NO atmosphere, NO2 acts as an intermediate which oxidizes soot to CO2 at a lower temperature with itself reduced to NO or N2, contributing to the high catalytic performance in simultaneous removal of NOx and soot.

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