Enhanced activity of vanadia supported on microporous titania for the selective catalytic reduction of NO with NH₃: Effect of promoters

Vanadium oxide-based catalysts are considered a promising catalyst for selective catalytic reduction (SCR) of NO with NH₃, which is an effective NO_x removal technology. As environmental issues have garnered more attention, however, improvements to vanadium-based SCR catalysts are strongly required. In a previous study, we found that vanadium oxide on microporous titania as a support (V/MPTiO₂) has certain advantages, such as improved thermal stability and more suppressed N₂O formation, over the use of conventional nanoparticle titania (DT-51) as a support. In this study, widely used promoters, such as W, Sb, and Mo, were added to V/MPTiO₂ to investigate whether they have promoting effects on V/MPTiO₂ as well. Among these promoters added catalysts, the W and Mo were found to have significant promoting effects on the enhancement of deNO_x activities at low temperatures, while the addition of Sb to V/MPTiO₂ tended to have a negative effect on the SCR activity. Based on the characterizations, including laser Raman, H₂-temperature programmed reduction (H₂-TPR), and in situ diffuse reflectance infrared Fourier transform (in situ DRIFT) analysis, we found that the addition of W and Mo increased the degree of polymerization in V/MPTiO₂, which generated more reactive vanadia species. Hence, such changes, resulting from the addition of W and Mo promoters to V/MPTiO₂, yielded enhanced catalytic activity at low temperatures.