Getting insight into the influence of SO2 on TiO2/CeO2 for the selective catalytic reduction of NO by NH3.

A series of inverse TiO 2 /CeO 2 catalysts were prepared by the impregnation method and their catalytic performances for the selective catalytic reduction of NO by NH 3 have been tested with and without SO 2 and/or H 2 O. Compared with the normally discussed CeO 2 /TiO 2 catalyst, the advantage of inverse TiO 2 /CeO 2 catalyst was not only shown a good low temperature catalytic activity (150–250 °C), but also exhibited much better SO 2 resistance performances with the existence of 200 ppm SO 2 and/or 5 vol.% H 2 O at 300 °C. Furthermore, SO 2 had more significant inhibitory effect on catalytic activity than H 2 O based on the configuration differences of Ce–Ti-based catalysts. These catalysts were investigated by means of TG-DTA, XRD, BET, in situ DRIFT, XPS and H 2 -TPR. The results demonstrated that the sulfation of these samples under reactive conditions mainly generated three different kinds of sulfate species including NH 4 HSO 4 , surface and bulk-like metal sulfates (mainly interacted with cerium species). The formed metal sulfates blocked the active sites of Ce–O–Ti and resulted in the deactivation of CeO 2 /TiO 2 . Although metal sulfates were also formed over TiO 2 /CeO 2 , NH 3 -SCR could still proceed and that was similar as the reaction system with the use of sulfated CeO 2 as the catalyst. Meanwhile, the interactions between SO 2 and Ce–Ti-based catalysts were discussed in detail and an adsorption model of SO 2 was proposed. [ABSTRACT FROM AUTHOR]