Study of NO removal and resistance to SO2 and H2O of MnOx/TiO2, MnOx/ZrO2 and MnOx/ZrO2–TiO2

Abstract MnO x /TiO 2 , MnO x /ZrO 2 and MnO x /ZrO 2 –TiO 2 were prepared by impregnation and NO removal was evaluated in a fixed‒bed reactor under simulated reactive gas. All samples were characterized by various technologies. The results showed that MnO x /ZrO 2 –TiO 2 had good selective catalytic reduction activity between 80–360 °C and excellent resistance to H 2 O at 200 °C for 30 h and achieved 80% NO x removal efficiency at 140 °C. The NO removal efficiency of MnO x /ZrO 2 was only 45–80%, and that of MnO x /TiO 2 was 100% at 240–360 °C. However, their tolerance to H 2 O was not as good as MnO x /ZrO 2 –TiO 2 . When SO 2 was induced into reactive gas, the NO removal efficiency of MnO x /ZrO 2 at 200 °C was maintained 70% for 34 h, but that of MnO x /TiO 2 decreased rapidly. MnO x /ZrO 2 –TiO 2 maintained 100% NO removal efficiency for 5 h and decreased gradually. After SO 2 was stopped, NO removal ability wasn’t recovered, indicating that deactivation of catalyst was irreversible. TiO 2 can improve the texture properties, and the surface area and total pore volume of MnO x /TiO 2 reached 313 m 2 /g and 0.38 m 3 /g. The existence of zirconium oxide significantly increased the concentration of Mn 4+ and O β on the surface of catalysts. MnO x /ZrO 2 –TiO 2 had wide surface acidity, which improved NH 3 adsorption. After SO 2 resistance testing, Mn 4+ content on the surface of catalysts decreased whereas Mn 3+ obviously increased. SO 2 could be oxidized by MnO x to SO 3 , and SO 3 was adsorbed on ZrO 2 or TiO 2 to form zirconium sulfate or titanyl sulfate. (NH 4 ) 2 SO 4 was formed on singe ZrO 2 or TiO 2 carrier. These sulfates increased the surface acidity, resulting in a change of NO removal ability.