Low-temperature catalytic reduction of nitrogen oxides with ammonia over supported manganese oxide catalysts

摘要

MnOx supported on γ-Al_2O_3, TiO_2, Y-ZrO_2 and SiO_2 was prepared by an impregnation and a deposition-precipitation method, and their catalytic activities for the low-temperature selective catalytic reduction (SCR) of NOx with NH_3 in the presence of excess O_2 were examined. The catalytic activity of the catalysts prepared by a deposition-precipitation method was higher than that of catalysts prepared by an impregnation method. The activity follows in the order: MnOx/TiO_2≈MnOx/γ-Al_2O_3 > MnOx/SiO_2 > MnOx/Y-ZrO_2. Supported MnOx catalysts prepared by a deposition-precipitation method appeared to have an amorphous manganese oxide phase and those prepared by an impregnation method exhibited a crystalline MnO_2 phase, respectively. The addition of SO_2 with H_2O in the feeding gas slightly deactivates the SCR activity of MnOx/TiO_2 catalysts.