Promotional effects of Titanium additive on the surface properties, active sites and catalytic activity of W/CeZrOx monolithic catalyst for the selective catalytic reduction of NOx with NH3

摘要

CeZrTixO(2) mixed oxides were prepared by a co-precipitation method, and serial WO3/CeZrTixO(2) catalysts were prepared to investigate the influence of doping TiO2 into CeZrO2 on the catalytic performance of selective catalytic reduction of NOx with NH3. The activity results showed that the introduction of appropriate amount of TiO2 could effectively improve the catalytic performance. WO3/CeZrTi200(2) with 20 wt.% TiO2 showed better deNO(x) activity and sulfur/water vapor tolerance than W/CeZrO2. Several techniques, including N-2 physisorption, XRD, XPS, H-2-TPR, NH3-TPD and in situ DRIFTS, were employed to characterize catalysts. The results indicated that doping TiO2 led to the formation of cerium-zirconium titanium solid solution with larger surface area. The interactions among metal oxides could enhance the redox properties of the catalyst, which was helpful to the improvement of the low-temperature NH3-SCR activity. Moreover, the addition of TiO2 promoted the adsorption and activation of NH3 and increased the reactivity of adsorbed nitrate species with NH3 species, which significantly affected the NH3-SCR performance. Finally, the results of in situ DRIFTS demonstrated that the NH3-SCR reaction mainly followed the Langmuir-Hinshelwood mechanism over W/CeZrO2 and W/CeZfFi(2)OO(2) catalysts at 200 degrees C. (C) 2017 Elsevier B.V. All rights reserved.