Influence of tungsten on the activity of a Mn/Ce/W/Ti catalyst for the selective catalytic reduction of NO with NH3 at low temperatures

The influence of tungsten in the Mn/Ce/W/Ti catalyst system on the activity and SO2 induced deactivation of the catalyst was evaluated. The properties of the catalyst were evaluated using physicochemical measurements, including Brunauer-Emmett-Teller (BET) surface area, X-ray photoelectron spectroscopy (XPS), NH3 temperature-programmed desorption (TPD), X-ray diffraction (XRD), and H-2 temperature-programmed reduction (H-2-TPR) analyses. The Mn4+ ratio increased with the addition of Ce and W to the Mn/Ti system. The Mn/Ce/W/Ti catalyst, prepared by controlling the Mn4+ ratio through the addition of Ce and W to Mn/Ti, exhibited excellent activity in the range of 120-200 degrees C. The catalyst efficiency was positively correlated with NH3 adsorption. The catalytic activity and surface area of the Mn/Ce/5W/Ti catalyst (containing 5 wt% tungsten) were optimal, but decreased at higher tungsten loadings. Increasing the Ce3+ ratio in Mn/Ce/W/Ti increased the selective catalytic reduction (SCR) activity. Mn/Ti and Mn/Ce/Ti were rapidly deactivated upon the injection of SO2 in the SCR reaction. However, the Mn/Ce/5W/Ti catalyst exhibited excellent resistance to SO2 induced deactivation. Thus, the addition of tungsten to Mn/Ce/Ti resulted in excellent NO conversion and SO2 resistance. (C) 2015 Elsevier B.V. All rights reserved.