Name: Development and characterization of thermally stable supported V–W–TiO<sub>2</sub> catalysts for mobile NH<sub>3</sub>–SCR applications
Description: 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.
DOI: 10.6084/M9.FIGSHARE.4641169.V1
Resository: https://tandf.figshare.com
Start date: 2017-01-01 00:00:00 UTC
End date:
Related Article: Development and characterization of thermally stable supported V–W–TiO2 catalysts for mobile NH3–SCR applications
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