In situ-DRIFTS Study of Sb–V–CeO₂/TiO₂ Catalyst Under Standard and Fast NH₃-SCR Conditions

In this study, the NO_x conversion under standard and fast SCR conditions on the Sb–V–CeO₂/TiO₂ catalyst has been conducted in the temperature range of 150–400 °C. The Sb–V–CeO₂/TiO₂ catalyst, under both fast and standard NH₃-SCR conditions, showed higher NO_x conversion than the commercial V₂O₅/WO₃–TiO₂ catalyst at low temperatures. In comparison to the V₂O₅/WO₃–TiO₂ catalyst, the NO oxidation to NO₂ was promoted for the Sb–V–CeO₂/TiO₂ catalyst at the temperatures between 150 and 400 °C. The in-situ DRIFTS studies at 200 °C on the Sb–V–CeO₂/TiO₂ catalyst surface indicated the IR bands assigned to NO₂, nitrate species and ammonia adsorbed species assigned to Brønsted and Lewis acid sites under both standard and fast SCR conditions. Furthermore, in-situ DRIFTS results of Sb–V–CeO₂/TiO₂ catalyst revealed that the formation of surface adsorbed NO₂, bridged nitrate and bidentate nitrate species. The reduction of nitrates to nitrites is induced by NO₂, which reacts with the adsorbed ammonium species forming intermediate NH₄NO₂. Eventually, this is converted to N₂ and H₂O in both SCR conditions.