A new view on the relations between tungsten and vanadium in V2O5WO3/TiO2 catalysts for the selective reduction of NO with NH3

• Published in: Journal of catalysis 2012-02, Vol.286, p.237-247
• Main Authors: Kompio, Patrick G.W.A., Brückner, Angelika, Hipler, Frank, Auer, Gerhard, Löffler, Elke, Grünert, Wolfgang
• Format: Article
• Language: English
• Subjects: Ammonia; EPR; Selective catalytic reduction; Temperature-programmed reduction; TiO2; V2O5; WO3 promotor
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2011.11.008

In spontaneous arrangement of surface V and W oxide species on anatase, a well-mixed surface oxide phase is formed, with surface W oxide species preventing the formation of extended two-dimensional vanadium oxide islands. [Display omitted] ► Comparative EPR studies of W-free and W-containing V2O5/TiO2 catalyst show extensive V oxide island formation in the former, more isolated V oxide species in the latter. ► TPR allows differentiating surface W oxide species in contact with surface V oxide species from those interacting with surface W oxide species only. ► Spontaneous arrangement of surface V and W oxide species on anatase leads to a well-mixed surface oxide phase instead of segregates surface V (W) oxide islands. The relation between tungsten and vanadium oxide species in V2O5WO3/TiO2 catalysts for the selective catalytic reduction of nitrogen oxides by ammonia was studied with two series of catalysts containing 0.5–5wt.% V2O5 and 0 or 10wt.% WO3 impregnated onto a high surface-area titania hydrate of anatase structure to keep theoretical surface coverages of the transition metal oxides ⩽1. The catalysts, which were investigated by XRD, nitrogen physisorption, Raman and EPR spectroscopy, temperature-programmed reduction (TPR), and catalytic reduction studies, all exhibited the well-known acceleration of the SCR reaction by the tungsten promoter. From the EPR spectra and the TPR profiles, it was concluded that the presence of tungsten induces the formation of a surface oxide phase with intimate mixing between vanadium and tungsten oxide species instead of pronounced surface vanadium oxide island formation, which was found in the absence of tungsten. This suggests that the promotional effect of tungsten may originate from a direct influence on the neighboring vanadium oxide species or from the disruption of too large surface vanadium oxide ensembles.