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

MnOx supported on gamma-Al2O3, TiO2, Y-ZrO2 and SiO2 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 NH3 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/TiO2 approximate to MnOx/gamma-Al2O3 > MnOx/SiO2 > MnOx/Y-ZrO2. 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 MnO2 phase, respectively. The addition of SO2 with H2O in the feeding gas slightly deactivates the SCR activity of MnOx/TiO2 catalysts.