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

Nb doped MnCe_0.2O_x complex oxides catalysts prepared via a homogeneous precipitation method were investigated for synergistic catalytic removal of NO_x and chlorobenzene (CB) at low temperatures. The MnNb_0.4Ce_0.2O_x catalyst with a molar ratio of Nb/Mn = 0.4 exhibits excellent activity and the NO_x and CB removal efficiency reaches 94.5% and 96% at 220 °C, respectively. Furthermore, the NO_x and CB removal efficiency of MnNb_0.4Ce_0.2O_x still remains above 80% after injecting 300 ppm SO₂ and 7 vol% H₂O for 36 h. In addition, the presence of CB and NO_x + NH₃ can improve the NO_x and CB removal efficiency of MnNb_0.4Ce_0.2O_x, respectively. The analysis results from N₂-BET, Py-IR, H₂-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 MnCe_0.2O_x at 100–250 °C. Moreover, the molecular migration process of NO_x, NH₃, CB and SO₂ in NH₃-SCR and CB oxidation reaction over MnNb_0.4Ce_0.2O_x 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 MnNb_0.4Ce_0.2O_x is inhibited effectively by the introduction of Nb in the presence of SO₂ and H₂O. Moreover, Nb additives also enhance the structural stability of MnNb_0.4Ce_0.2O_x, due to the interactions among Mn, Nb and Ce. The NH₃-TPD, H₂-TPR and in situ DRIFTS results also confirm that the MnNb_0.4Ce_0.2O_x still retains abundant acid sites and high redox ability in the presence of SO₂ and H₂O. In summary, MnNb_0.4Ce_0.2O_x catalysts represent a promising and effective candidate for controlling NO_x and CB at low temperatures.