New CeO_2-TiO_2, WO_3-TiO_2 and WO_3-CeO_2-TiO_2 mesoporous aerogel catalysts for the low temperature selective catalytic reduction of NO by NH_3

摘要

New mesoporous and well-structured aerogel catalysts (CeO2-TiO2, WO3-TiO2 and WO3-CeO2-TiO2) were elaborated via the sol-gel method, characterized by means of various techniques (XRD; N-2-Physisorption at 77 K; NH3-TPD; H-2-TPR; DRUV-Vis spectroscopy) and evaluated in the selective catalytic reduction (SCR) of NO by NH3. The results reveal that all the aerogel catalysts develop essentially the diffraction peaks of TiO2 anatase phase and are classified as mesoporous materials with a high surface area (70 S-BET 106 m(2) g(-1)), large porosity (0.27 V-PT 0.46 cm(3) g(-1)) and nanometer size of crystallites (8-15 nm). The addition of Ce and/or W influences differently the structure, texture, crystallites size, surface oxygen concentration, total acidity and redox ability of aerogel samples and clearly affects their NO-SCR activity which follows this order: TiO2 WO3-TiO2 CeO2-TiO2 WO3-CeO2-TiO2. It was also found that cerium species are more active in the low temperature NO-SCR reaction than tungsten ones (NO conversions obtained at 300 degrees C using CeO2-TiO2 and WO3-TiO2 were 75 and 0%, respectively). On the other hand, it was suggested that the interactions between Ce and W species play a key role in improving the reactivity of WO3-CeO2-TiO2 catalyst in the SCR of NO by NH3. Interestingly, the NO conversion into N-2 reaches 85% at 300 degrees C and exceeds 90% between 320 and 400 degrees C over this novel meso-structured aerogel catalyst.