Promotional effect of ceria on the catalytic behaviour of new V2O5–WO3–TiO2 aerogel solids for the DeNOx process

Abstract

New cerium and/or tungsten modified V2O5–TiO2 aerogel catalysts (V2O5–TiO2,V2O5–WO3–TiO2, V2O5–CeO2–TiO2 and V2O5–WO3–CeO2–TiO2) were successfully developed, by associating the sol gel procedure and supercritical drying approach. A combination of various analytical techniques, including XRD, N2-Physisorption at 77 ​K, DRUV-Vis spectroscopy, NH3-TPD and H2-TPR, was used to characterize the obtained solids. Their catalytic performances were evaluated in the low temperature NO-SCR by NH3. The results reveal that all the materials exhibit high cristallinity of TiO2 anatase phase and developed mesoporous texture. The addition of tungsten (W) increases the surface acidity of V2O5–TiO2 and thereby enhances its reactivity at high temperatures (>420 ​°C). However, the addition of cerium (Ce) improves the redox properties of the latter catalyst and increases significantly its NO-SCR reactivity, especially at low temperatures. The NO-SCR activity increases over the aerogel systems, in the 200–400 ​°C temperature range, following this order: V2O5–WO3–TiO2 ​< ​V2O5–TiO2 ​< ​V2O5–CeO2–TiO2 ​< ​V2O5–WO3–CeO2–TiO2. The new V2O5–WO3–CeO2–TiO2 system was found to be the most active catalyst for converting NO into N2 (with 60% and 90% NO conversions at 250 ​°C and between 320 and 420 ​°C, respectively). The highest SCR activity of this new aerogel solid if compared to the other samples was essentially correlated with a good reactivity of its acidic and redox sites which in turn was related to the existence of strong interactions between cerium and the other active elements (mostly Ce↔ V and Ce ↔ W).