Sulfation effect of Ce/TiO 2 catalyst for the selective catalytic reduction of NO x with NH 3 : mechanism and kinetic studies.

Ceria-based catalysts are competitive substitutes for the commercial SCR catalysts due to their high SCR activity and excellent redox performance. For a better understanding of the SO 2 poisoning mechanism over ceria-based catalysts, the sulfation effect of the Ce/TiO 2 catalyst on the SCR activity over a wide reaction temperature range was systematically studied via comprehensive characterizations, in situ DRIFT studies and kinetic studies. The results demonstrated that the NO conversion at 150 °C is significantly inhibited by the formation of cerium sulfites/sulfates due to the inhibited redox properties and excessive adsorption of NH 3 , which restrict the dissociation of NH 3 to NH 2 , resulting in a much lower reaction rate of E-R reaction over the sulfated Ce/TiO 2 catalyst. With the increase in the reaction temperature, the reaction rate of the E-R reaction significantly increased due to the improved redox properties and weakened adsorption of NH 3 . Moreover, the rate of the C-O reaction over the sulfated Ce/TiO 2 catalysts is obviously lower than that of the fresh Ce/TiO 2 catalyst. The promotion of NO conversion over the sulfated catalyst at 330 °C is attributed to both the increase in the reaction rate of E-R reaction and the inhibition of the C-O reaction.