Steady-State and Transient Reactivity Study of TiO_2-Supported V_2O_5-WO_3 De-NO_x Catalysts: Relevance of the Vanadium-Tungsten Interaction on the Catalytic Activity

摘要

The reactivity of ternary V_2O_5-WO_3/TiO_2 de-NO_x catalysts (V_2O_5 = 0-1.47% w/w, WO_3 = 0-9% w/w) in the selective catalytic reduction (SCR) reaction is investigated under steady-state and transient conditions. The results indicate that over the investigated catalysts the SCR reaction occurs via a redox mechanism and that the rate-determining step of the reaction is the catalyst reoxidation process. The reactivity of the V_2O_5—WO_3/TiO_2 catalysts increases on increasing either the V_2O_5 or the WO_3 loading; the reactivity of V and/or W in the ternary catalysts is higher than that of the corresponding binary samples. A synergism between the TiO_2-supported V and W surface oxide species in the SCR reaction is suggested, that is exploited in the enhancement of the catalyst redox properties of the samples. Accordingly, tungsta increases the rate of the SCR reaction of V_2O_5/TiO_2 catalysts by favoring the catalyst reoxidation by gas-phase oxygen.