Tailored temperature window of MnOx-CeO2 SCR catalyst by addition of acidic metal oxides

Abstract A MnO x -CeO 2 catalyst was modified with various acidic metal oxides (Nb 2 O 5 , WO 3 , and MoO 3 ) using a sol-gel method. The activities of the obtained catalysts were measured for the selective catalytic reduction (SCR) of NO x with NH 3 to screen suitable acidic metal oxides for different temperature windows. The catalytic activities for NO and NH 3 oxidation were also evaluated. The catalysts were characterized by X-ray diffraction, N 2 adsorption, H 2 temperature-programmed reduction, NH 3 /NO x temperature-programmed desorption analyses, and infrared spectroscopic measurements of NH 3 /NO x adsorption. The MnO x -CeO 2 catalyst exhibited the greatest low-temperature (100–150 °C) activity. The addition of acidic metal oxides weakened the redox properties of the catalyst, resulting in inhibition of the partial oxidation of the adsorbed NH 3 and NO 2 -assisted fast SCR reactions. Meanwhile, the oxidation of NH 3 at relatively high temperatures (250–350 °C) was suppressed, and the adsorption of NH 3 on Bronsted and Lewis acid sites was strengthened. Consequently, the temperature window of SCR reaction shifted to higher temperatures in the order Nb 2 O 5 3 3 .