A new V2O5–MoO3–TiO2–SO42− nanostructured aerogel catalyst for diesel DeNOx technology

Abstract

A new V₂O₅–MoO₃–TiO₂–SO₄²⁻ nanostructured aerogel system, containing V and Mo loadings representative of the V₂O₅–MoO₃/TiO₂ commercial SCR catalyst, was developed via a one step sol–gel method combined with the supercritical drying approach for the low temperature selective catalytic reduction of NO by NH₃, in excess O₂. The new V₂O₅–MoO₃–TiO₂–SO₄²⁻ catalyst was analysed via XRD, N₂-physisorption, H₂-TPR, NH₃-TPD, Raman spectroscopy, XPS and DR UV-vis spectroscopy. The elaboration and characterization of TiO₂, V₂O₅–TiO₂, MoO₃–TiO₂, V₂O₅–MoO₃–TiO₂, TiO₂–SO₄²⁻, V₂O₅–TiO₂–SO₄²⁻ and MoO₃–TiO₂–SO₄²⁻ aerogel samples were also reported in this work. The results prove the successful synthesis of nanostructured aerogel materials with good crystallinity of the TiO₂ anatase phase, a developed mesoporous texture and a nanometer size as new SCR catalysts. V, Mo and SO₄²⁻ were found to be highly dispersed on the TiO₂ surface, and their presence and the diverse interactions developed between them strongly affect the physicochemical properties and catalytic behaviour of the derived sol–gel powders. Among all the samples investigated, the new V₂O₅–MoO₃–TiO₂–SO₄²⁻ aerogel was found to be the most efficient catalyst for the low temperature NO-SCR: compared to a V₂O₅–WO₃/TiO₂ commercial catalyst (EUROCAT), it demonstrates similar SCR activity in the 200–375 °C temperature range, but, at higher temperatures (375–500 °C), it exhibits superior catalytic performance. A complete conversion of NO into N₂ (100%) was achieved in the 450–500 °C temperature range over the new V₂O₅–MoO₃–TiO₂–SO₄²⁻ nanostructured aerogel catalyst, when the NH₃-SCR reaction was realized using 1000 ppm NO and 1000 ppm NH₃, in the presence of 3.5% H₂O.