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

MnOx/TiO2, MnO/ZrO2 and MnOx/ZrO2-TiO2 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 MnOx/ZrO2-TiO2 had good selective catalytic reduction activity between 80-360 degrees C and excellent resistance to H2O at 200 degrees C for 30 h and achieved 80% NOx removal efficiency at 140 degrees C. The NO removal efficiency of MnO/ZrO2 was only 45-80%, and that of MnO/TiO2 was 100% at 240-360 degrees C. However, their tolerance to H2O was not as good as MnOx/ZrO2-TiO2. When SO2 was induced into reactive gas, the NO removal efficiency of MnOx/ZrO2 at 200 degrees C was maintained 70% for 34 h, but that of MnO/TiO2 decreased rapidly. MnOx/Zro(2)-TiO2 maintained 100% NO removal efficiency for 5 h and decreased gradually. After SO2 was stopped, NO removal ability wasn't recovered, indicating that deactivation of catalyst was irreversible. TiO2 can improve the texture properties, and the surface area and total pore volume of MnO/TiO2 reached 313 m(2)/g and 0.38 m(3)/g. The existence of zirconium oxide significantly increased the concentration of Mn4+ and O-beta on the surface of catalysts. MnOx/ZrO2-TiO2 had wide surface acidity, which improved NH3 adsorption. After SO2 resistance testing, Mn4+ content on the surface of catalysts decreased whereas Mn3+ obviously increased. SO2 could be oxidized by MnOx to SO3, and SO3 was adsorbed on ZrO2 or TiO2 to form zirconium sulfate or titanyl sulfate. (NH4)(2)SO4 was formed on singe ZrO2 or TiO2 carrier. These sulfates increased the surface acidity, resulting in a change of NO removal ability.