Effect of acidic components (SO42- and WO3) on the surface acidity, redox ability and NH3-SCR activity of new CeO2-TiO2 nanoporous aerogel catalysts: A comparative study

Selective catalytic reduction (SCR) of nitrogen oxide (NO) by ammonia (NH3) was studied in this work over new sulfate (SO42-) or tungsta (WO3) modified CeO2-TiO2 aerogel catalysts. The catalytic systems were elaborated via sol gel method then characterized by: XRD, N2-Physisorption at 77 K, DRUV–vis, NH3-TPD and H2-TPR. It was revealed that the nature of acidic components influences differently the texture, surface oxygen concentration, acidity, reducibility and NH3-SCR activity of new Ce-based catalysts. Hence, the incorporation of sulfate modifies the nature of Ce species, improves their dispersion through the Ce-SO42- interactions and, particularly, generates new strong acid sites which display superior catalytic performance at high temperature NO reduction (NO conversion into N2 > 90 % between 450 and 500 °C over CeO2-TiO2-SO42- catalyst). However, the addition of tungsta affects slightly the surface acidity of CeO2-TiO2 catalyst but it induces the creation of more reactive surface oxygen and new redox sites at its surface (mainly due to the existence of W-Ce interactions) leading to highly active WO3-CeO2-TiO2 system for the low temperature NH3-SCR reaction with above 90 % NO conversion into N2 between 320 and 400 °C.