Acidity, surface species, and catalytic activity study on V2O5-WO3/TiO2 nanotube catalysts for selective NO reduction by NH3

• Published in: Fuel (Guildford) 2017-06, Vol.198, p.123-133
• Main Authors: Aguilar-Romero, M., Camposeco, R., Castillo, S., Marín, J., Rodríguez-González, V., García-Serrano, Luz A., Mejía-Centeno, Isidro
• Format: Article
• Language: English
• Subjects: Acidity; Catalysts; Catalytic activity; Conversion; Hydrothermal treatment; Lewis acid; Low temperature; Microscopy; Nanotechnology; Nanotubes; NOx; SCR-process; Sulfur dioxide; Surface acidity; Temperature effects; Titanate nanotubes; Titanium dioxide; Tungsten oxides; V2O5-WO3 catalysts; Vanadium pentoxide; X ray photoelectron spectroscopy; X-ray diffraction
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2016.11.090

[Display omitted] •We analyze the acidity, redox properties and catalytic activity of V-W/NT catalysts.•Reduced V4+/V5+ species and Lewis and Brønsted acid sites promote the NO conversion.•V2O5 increases Brønsted and Lewis acid sites. Lewis acid sites are promoted by WO3.•V-W/NT presents higher catalytic activity than W/NT and V/NT catalysts.•NO conversion is not affected by SO2, but water inhibits the catalytic activity. In this work, we report the catalytic activity of V2O5/TiO2, V2O5-WO3/TiO2 and WO3/TiO2-nanotube model catalysts in removing NO with NH3 via the SCR process. The catalytic activity includes the effect of SO2 and H2O. We also analyze the effect of WO3 and V2O5 loading upon the surface acidity of the nanotubes, and the effect of WO3 on the V4+/V5+ ratio, and its correlation with the catalytic activity. TiO2-nanotubes (NT), employed as support, were prepared by hydrothermal treatment of TiO2 with NaOH. The catalysts were characterized by X-ray diffraction, HR-TEM microscopy, N2 physisorption, FTIR, H2-TPR, Raman and XPS. In general, we found that ternary catalysts (V2O5-WO3/NT) showed a higher NO conversion versus V2O5/NT and WO3/NT model catalysts. In fact, we found a high NO conversion (93%) over 3V-10W/NT catalyst at low temperature (380°C). In the presence of SO2 (50ppm) and H2O (5vol.%), NO conversion slightly decreases (from 93 to 80% at 380°C). The surface acidity (Brønsted and Lewis) of the nanotubes is the main parameter improved by adding V2O5. WO3 preferably modifies the Lewis acid sites of the nanotubes. Additionally, the structure and morphology of the nanotubes as well as the V4+/V5+ ratio, which depend on the metal loading, play an important role in the removal of NO at intermediate temperatures even in the presence of SO2 and H2O.