The role of ceria on the activity and SO2 resistance of catalysts for the selective catalytic reduction of NOx by NH3

Abstract We investigated the influence of Ce on the catalytic activity of V/Sb/Ce/Ti and its deactivation due to SO 2 . We studied the properties of the catalyst using physio-chemical techniques, including transmission infrared spectroscopy (IR), NH 3 and SO 2 temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), H 2 temperature programmed reduction (H 2 -TPR), and thermal gravimetric analysis (TGA). The catalysts V/Sb/Ti and V/Sb/Ce/Ti showed an excellent NOx conversion and N 2 selectivity in the temperature range of 200–400 °C. Increasing Bronsted acid sites and the NH 3 adsorption positively affected the efficiency of the catalyst. The Ce 4+ ratio increased upon the addition of Sb and V to Ce/Ti. The catalyst V/Sb/Ce/Ti was prepared by controlling the Ce 4+ ratio and exhibited an excellent activity upon increasing the Ce 4+ ratio. The V/Sb/Ti (or V/W/Ti) showed one route in which NH 4 HSO 4 formed by converting SO 2 into SO 3 upon the injection of SO 2 in the selective catalytic reduction (SCR) reaction. In addition to this route, the reaction in the presence of V/Sb/Ce/Ti can proceed via a second route, in which Ce 2 (SO 4 ) 3 is formed in the reaction of Ce with SO 2 and O 2 . Thus, V/Sb/Ce/Ti can inhibit the formation of NH 4 HSO 4 due to the consumption of SO 2 in the formation of Ce 2 (SO 4 ) 3 . Therefore, V/Sb/Ce/Ti was found to have excellent SO 2 resistance compared to V/Sb/Ti (or V/W/Ti).