Develop high efficient of NH3-SCR catalysts with wide temperature range by ball-milled method

Abstract To develop high efficient NH3-SCR catalysts with wide temperature range, a series of novel catalysts based on MnOx-CeO2/TiO2 and V2O5-WO3/TiO2 with various mixing-ratios were prepared via ball-milled method for selective catalytic reduction of NO by NH3. N2-Sorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and in-situ diffuse reflectance infrared transform spectroscopy (in-situ DRIFTS) were used to characterize the catalysts. The ball-milling catalysts exhibited over 90% NO conversion in 200–400 °C, good N2 selectivity and high poison resistance to SO2 and H2O in broad temperature window when compared to their original materials (e.g., the 5MnCe/Ti-5VW/Ti (BM-6 h). The good SCR performance of xMnCe/Ti-yVW/Ti (BM-6 h) indicated that the milled-mixing method was a promising way in developing wide temperature range SCR catalysts. The XPS results showed that the ratio of (V3++V4+)/Vn+, Mn4+/Mn3+ and Ce3+/Ce4+ on the surface of xMnCe/Ti-yVW/Ti (BM-6 h) samples were higher than that on the MnCe/Ti(raw/BM-6 h) and VW/Ti(raw/BM-6 h), and increased as the duration of ball-milled process extended. The possible routes for electron transfer between the V, Mn and Ce components on the ball-milled mixing catalysts were proposed. The DRIFTS results showed that the surface of 5MnCe/Ti-5VW/Ti (BM-6 h) was mainly covered by ionic NH4+ at low temperature due to abundant Bronsted acid sites. The ionic NH4+ reacted with NO2 nitro compounds and gaseous NO via “fast SCR” reaction route at low temperature. In addition, the coordinated NH3 dominated the SCR reaction by reacting with gaseous NO in “standard SCR” route at high temperature (i.e. ≥350 °C).