Development and characterization of thermally stable supported V–W–TiO2 catalysts for mobile NH3–SCR applications. (February 2015)

• Record Type: Journal Article
• Authors: Beale, Andrew M.; Lezcano-Gonzalez, Ines; Maunula, Teuvo; Palgrave, Robert G.
• Is Part Of: Catalysis, structure & reactivity. Volume 1:Number 1(2015)
• Page Start: 25
• Page End: 34
• Publication Date: 2015-02
• Subjects: Catalysts -- Periodicals; Catalysis -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; 660.2995
• DOI: 10.1179/2055075814Y.0000000005
• Languages: English
• ISSNs: 2055-074X

Abstract

<abstract> <title> <x content-type="archive" xml:space="preserve">Abstract</x> </title> <p> <graphic xlink:href="ark:/27927/pgh3xb8196r" position="anchor" orientation="portrait" xmlns:xlink="http://www.w3.org/1999/xlink" /> </p> <p>Vanadium based catalysts supported on a mixture of tungsten and titanium oxide (V<sub>2</sub>O<sub>5</sub>/WO<sub>3</sub>–TiO<sub>2</sub>) are known to be highly active for ammonia selective catalytic reduction (NH<sub>3</sub>–SCR) of NO<sub>x</sub> species for heavy-duty mobile applications. However they are also known to be sensitive to high temperatures which leads to both sintering of the anatase TiO<sub>2</sub> support and a first order phase transition to rutile at temperatures >600°C. Here we report our attempts to use SiO<sub>2</sub> to stabilize the TiO<sub>2</sub> anatase phase and to compare its catalytic activity with that of a non-stabilized V<sub>2</sub>O<sub>5</sub>/WO<sub>3</sub>–TiO<sub>2</sub> catalyst after thermal aging up to 800°C. Detailed characterization using spectroscopic (Raman, UV–vis, X-ray absorption spectroscopy), scattering and techniques providing information on the catalytic surface (Brunauer–Emmet–Teller, NH<sub>3</sub> adsorption) have also been performed in order to understand the impact of high temperatures on component speciation and the catalytic interface. Results show that non-stabilized V<sub>2</sub>O<sub>5</sub>/WO<sub>3</sub>–TiO<sub>2</sub> catalysts are initially stable after thermal aging at 600°C but on heating above this temperature a marked drop in catalytic activity is observed as a result of sintering and phase transformation of Anatase into Rutile TiO<sub>2</sub> and phase segregation of initially highly dispersed WO<sub>3</sub> and polymeric V<sub>2</sub>O<sub>5</sub> into monoclinic WO<sub>3</sub> and V<sub>2</sub>O<sub>3</sub> crystallites. Similar behavior was observed for the 4–5 wt-% of SiO<sub>2</sub>-stabilised sample after aging above 700°C, importantly therefore, offset by some ∼100°C in comparison to the unstabilised sample.</p> </abstract>