Bulk Vanadium Oxide versus Conventional V₂O₅/TiO₂: NH₃–SCR Catalysts Working at a Low Temperature Below 150 °C

Practical catalysts that work at a low temperature for selective catalytic reduction of NOx using NH3 (NH3–SCR) have been required to treat NOx at the outlet temperature in boiler systems (100–150 °C). In this paper, we report bulk vanadium oxide catalysts that show NH3–SCR activity at a low temperature below 150 °C. Defective bulk vanadium oxide (V(V)+V(IV)) catalysts were synthesized by the calcination of vanadium(IV)-oxalate at 270 °C (1–4 h). The reaction rate per mol of surface vanadium atom of the catalyst calcined at 270 °C for 2 h (V 270-2, 6.4 × 10–2 molNO molV–1 s–1) was 10–14 times faster than those of conventional 1–9 wt % V2O5/TiO2 (4.5 × 10–3–6.1 × 10–3 molNO molV–1 s–1), indicating that bulk vanadium oxide is more favorable for NH3–SCR and V(IV) species enhance the activity. The NH3–SCR of V 270-2 is driven by the Lewis acid mechanism, which proceeds faster than the Brønsted acid mechanism.