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

Highlights: • New VWTi and VWCeTi nanostructured mesoporous aerogel catalysts for NO-SCR by NH₃. • WO₃ improves surface acidity and high temperature NO-SCR activity of VTi catalyst. • CeO₂ enhances redox properties and low temperature NO-SCR activity of VTi system. • NO-SCR activity increases at 200-400 °C as follow: VWTi < VTi• A synergism in the NO-SCR is related to Ce ↔ V and Ce ↔W strong interactions. New cerium and/or tungsten modified V₂O₅–TiO₂ aerogel catalysts (V₂O₅–TiO₂,V₂O₅–WO₃–TiO_2, 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 77K, 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–TiO₂2O₅–TiO₂2O₅–CeO₂–TiO₂2O₅–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).