In Situ XANES Characterization of V₂O₅/TiO₂–SiO₂–MoO₃ Catalyst for Selective Catalytic Reduction of NO by NH₃

Abstract

The structures of V2O5 catalysts for the selective catalytic reduction (SCR) of NO by NH3 at low temperatures are investigated using in situ V K-edge X-ray absorption near-edge structure measurements. The V2O5 catalyst supported on TiO2–SiO2–MoO3 mixed oxide (V/TSM) showed a significantly steep increase in the main-edge energy at the beginning of the reaction. The results indicate that the excellent NH3-SCR catalytic activity of V/TSM can be ascribed to the remarkable V4+-to-V5+ reoxidation capability and easier V5+-to-V4+ reducibility. This improved redox reactivity is induced by the interaction of the highly dispersed polymeric vanadate with TSM solid solution and by the appropriate surface geometry of vanadium species, which enabled contact with NH3 and O2 in the gas phase. The results reported herein should enable the development of improved catalysts for NH3-SCR.

Deactivation Mechanism and Enhanced Durability of V2O5/TiO2–SiO2–MoO3 Catalysts for NH3−SCR in the Presence of SO2

“…VMo/TS and V/TSM are both commercially employed catalysts that have been developed based on the conventional VMo/TiO 2 catalyst. As we reported previously, among these V‐Mo catalysts, V/TSM exhibits a superior NH 3 −SCR activity at low temperatures owing to improved reducibility and reoxidizability between V 4+ and V 5+ in polymeric vanadates on the catalyst surface [47,50] …”

“…As we reported previously, among these V-Mo catalysts, V/TSM exhibits a superior NH 3 À SCR activity at low temperatures owing to improved reducibility and reoxidizability between V 4 + and V 5 + in polymeric vanadates on the catalyst surface. [47,50] While slight differences were observed in the initial activities at 200°C, all the catalysts exhibited almost constant conversions until 400 h. By contrast, the catalytic activity of VMo/TiO 2 quickly deteriorated at 175°C. V/TSM exhibited both superior durability and a higher initial catalytic activity, whereas the durability of VMo/TS was intermediate between those of VMo/ TiO 2 and V/TSM.…”

Catalytic Performance and Sulfur Dioxide Resistance of One-Pot Synthesized Fe-MCM-22 in Selective Catalytic Reduction of Nitrogen Oxides with Ammonia (NH3-SCR)—The Effect of Iron Content

“…The technology was developed in the 1970s in Japan and has become widespread around the world [5,6]. In recent years, the most common commercial catalytic system of NH 3 -SCR is V 2 O 5 -TiO 2 promoted with MoO 3 or WO 3 [7,8]. In fact, the catalyst exhibits satisfactory performance in the temperature range of 300-400 • C [9], however, it is not free from some significant 2 of 32 drawbacks [10,11].…”

Analogous Mechanistic Features of NH3-SCR over Vanadium Oxide and Copper Zeolite Catalysts

“…Although these catalysts are considered the state of the art, catalytic activities, especially at low temperatures, must be improved. It is, therefore, crucial to elucidate catalytic mechanisms, establish structure–activity relationships, and develop highly efficient catalysts based on precise catalyst-design guidelines. − …”