Sol–Gel Synthesized V₂O₅/TiO₂ Catalysts for NH₃-SCR: Effect of Calcination Temperature on Performance

Ammonia-based selective catalytic reduction (SCR) is essential for removing nitrogen oxides (NO_x) emitted from industrial furnaces and automobiles. Although commercial V₂O₅/TiO₂ catalysts are economically viable for NH₃-SCR, their poor catalytic activities limit their use to operating temperatures greater than 300 ℃, which prevents their use under low-temperature exhaust conditions. In this study, we employed a one-step sol–gel method to produce V₂O₅/TiO₂ catalysts and then compared their catalytic performances and physicochemical characteristics with those of a conventional impregnated V₂O₅/TiO₂ catalyst. This one-step approach resulted in catalysts that exhibited improved NO conversions; notably, the activity of sol–gel catalysts produced under optimized conditions was almost twice that of the conventional catalyst. In this study, catalyst calcination temperature was adjusted between 250 and 550 ℃. X-ray diffraction showed the crystallinity of the anatase TiO₂ phase increased with calcination temperature, but calcination temperatures (> 500 ℃) caused sintering and reduced BET surface area as determined using N₂ adsorption–desorption isotherms. X-ray photoelectron spectroscopy and NH₃ temperature-programmed desorption demonstrated that catalysts calcined at temperatures between 350 and 500 °C had optimal amounts of V⁴⁺ species, surface oxygen, and acidic sites, which are essential for catalytic activity. This study highlights that the one-step sol–gel technique provides a simple, cost-effective means of synthesizing high-performance V₂O₅/TiO₂ catalysts for low-temperature NH₃-SCR applications.