Synergetic catalytic removal of chlorobenzene and NOx from waste incineration exhaust over MnNb0.4Ce0.2Ox catalysts: Performance and mechanism study

Nb doped MnCe0.2Ox complex oxides catalysts prepared via a homogeneous precipitation method were investigated for synergistic catalytic removal of NOx and chlorobenzene (CB) at low temperatures. The MnNb0.4Ce0.2Ox catalyst with a molar ratio of Nb/Mn = 0.4 exhibits excellent activity and the NOx and CB removal efficiency reaches 94.5% and 96% at 220 degrees C, respectively. Furthermore, the NOx and CB removal efficiency of MnNb0.4Ce0.2Ox still remains above 80% after injecting 300 ppm SO2 and 7 vol% H2O for 36 h. In addition, the presence of CB and NOx + NH3 can improve the NOx and CB removal efficiency of MnNb0.4Ce0.2Ox respectively. The analysis results from N-2-BET, Py-IR, H-2-TPR and NH3-TPD reveal that the introduction of Nb increases the average pore size, pore volume and surface area, promoted the growth of Lewis acid amount obviously, and enhances redox ability of MnCe0.2Ox at 100-250 degrees C. Moreover, the molecular migration process of NOx, NH3, CB and SO2 in NH3-SCR and CB oxidation reaction over MnNb0.4Ce0.2Ox catalysts were systematically studied. In situ DRIFTS, FT-IR and XPS also confirm that the adsorption of sulfate species and SO2 on the surface of MnNb0.4Ce0.2Ox is inhibited effectively by the introduction of Nb in the presence of SO2 and H2O. Moreover, Nb additives also enhance the structural stability of MnNb0.4Ce0.2Ox,( )due to the interactions among Mn, Nb and Ce. The NH3-TPD, H-2-TPR and in situ DRIFTS results also confirm that the MnNb0.4Ce0.2Ox still retains abundant acid sites and high redox ability in the presence of SO2 and H2O. In summary, MnNb0.4Ce0.2Ox catalysts represent a promising and effective candidate for controlling NOx and CB at low temperatures. (C) 2020 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.