STEADY-STATE AND TRANSIENT REACTIVITY STUDY OF TIO2-SUPPORTED V2O5-WO3 DE-NOX CATALYSTS - RELEVANCE OF THE VANADIUM-TUNGSTEN INTERACTION ONTHE CATALYTIC ACTIVITY

The reactivity of ternary V2O5-WO3/TiO2 de-NOx catalysts (V2O5 = 0-1.4 7% w/w, WO3 = 0-9% w/w) in the selective catalytic reduction (SCR) rea ction is investigated under steady-state and transient conditions. The results indicate that over the investigated catalysts the SCR reactio n occurs via a redox mechanism and that the rate-determining step of t he reaction is the catalyst reoxidation process. The reactivity of the V2O5-WO3/TiO2 catalysts increases on increasing either the V2O5 or th e WO3 loading; the reactivity of V and/or W in the ternary catalysts i s higher than that of the corresponding binary samples. A synergism be tween the TiO2-supported V and W surface oxide species in the SCR reac tion is suggested, that is exploited in the enhancement of the catalys t redox properties of the samples. Accordingly, tungsta increases the rate of the SCR reaction of V2O5/TiO2 catalysts by favoring the cataly st reoxidation by gas-phase oxygen.