Tungsten modified MnOx-CeO2/ZrO2 monolith catalysts for selective catalytic reduction of NOx with ammonia

A series of WO3-ZrO2 carriers were prepared by co-precipitation method with different mass fractions (0 wt%, 5 wt%, 10 wt%, 15 wt% and 20 wt%) of WO3, and MnOx-CeO2/WO3-ZrO2 monolith catalysts were prepared for selective catalytic reduction of NOx with ammonia (NH3-SCR) in the presence of excessive O-2. The catalysts were characterized by N-2 adsorption-desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and NH3/NO temperature-programmed desorption (NH3/NO-TPD). The experimental results showed that, the tungsten modified monolith catalyst MnOx-CeO2/WO3-ZrO2 with the WO3 content 10 wt% had the best catalytic activity and the widest reaction window; it possessed a better thermal stability than V2O5/WO3/TiO2 catalyst, and showed a better H2O and SO2 tolerance than MnOx-CeO2/ZrO2. The characterization results indicated that MnOx-CeO2/10% WO3-ZrO2 had the best textural properties, a well-dispersed state of WO3, the lowest binding energy of Ce3+ 3d(5/2), the maximum value of Ce3+:Ce=20.7%, the suitable molar ratio of Mn:Ce approximate to 1, and a co-existence state of MnO2-Mn2O3. In addition, it had the most adsorbed sites of NH3 or NO species. The NOx conversion was more than 80% in the temperature range of 150 degrees C to 380 degrees C at the space velocity of 10,000 h(-1). It possessed better potential for practical application. (c) 2012 Elsevier Ltd. All rights reserved.