Promotional effect of doping SnO2 into TiO2 over a CeO2/TiO2 catalyst for selective catalytic reduction of NO by NH3

Abstract

Ti_xSn_1−xO₂ was prepared by a co-precipitation method, and a series of CeO₂/Ti_xSn_1−xO₂ samples were prepared to investigate the effect of doping SnO₂ into TiO₂ for selective catalytic reduction of NO by NH₃. The results of catalytic tests suggested that the catalyst with the optimal molar ratio (Ti : Sn = 1 : 1) exhibited the best catalytic performance. Moreover, the NO removal efficiency of CeO₂/Ti_0.5Sn_0.5O₂ was higher than that of CeO₂/TiO₂. The obtained samples were characterized by BET, XRD, H₂-TPR, XPS, NH₃-TPD and in situ DRIFT. The results revealed that the introduction of SnO₂ resulted in the formation of rutile-type Ti_0.5Sn_0.5O₂ solid solution with larger specific surface area and better thermal stability. The interactions between CeO₂ and the Ti_0.5Sn_0.5O₂ support could improve the redox performance of the catalyst, which was beneficial to the enhancement of catalytic activity at low temperature. Furthermore, doping SnO₂ enhanced the surface acid sites and weakened the adsorption of nitrates, which played an important role in the catalytic reaction process. Finally, in situ DRIFT demonstrated that the competition adsorption happened between bridging nitrates and NH₃ gas and the selective catalytic reduction of NO by NH₃ proceeded mainly via the Eley–Rideal mechanism over Ce/TiO₂ and Ce/Ti_0.5Sn_0.5O₂.