Ti02-supported V2O5 Catalysts

In a related set of catalysts a loading of 1% vanadium(v) oxide on titanium dioxide is used. These eatalysts are applied in selective catalytic reduction (SCR) reactions, i.e. the removal of NOx through selective reaction with ammonia from streams eontaining large volumes of o g gen. These eatalysts require the redox aetivity as diseussed above, but also an acidic functionality (to activate the seleetive reduetant (ammonia)). It transpires that the produet of reduetion of the surface V=0 groups (V-OH) is sufficiently acidie for this purpose. This means these V=0 species oriented into the reaction medium beeause of their interaction with Ti02 can act as both redox and acidic surface sites. The mechanism of the deNOx reaction has been extensively studied over these materials.  

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Lietti L., Forzatti P., Bregani F. (1996) "Steady-State and Trasient Reactivity Study of Ti02-Supported V2O5-WO3 DeNOx Catalysts Relevance of the Vanadium-Tungsten Interaction on the Catalytic Activity . Jnd. Chem. Eng. Res., 35, 3884-3892. 

Lietti L, Nova I, Foizatti P (2000) Selective catalytic reduction (SCR) of NO by NH3 over Ti02-supported V2O5-WO3 and V2O5-M0O3 catalysts. Topics in Catal 11/12 111-122... 

Ti02 supported V2O5 is more easily reduced to metallic vanadium then bulk V2O5, due to the interaction between the support and the active component. This interaction between support and active component has no influence on the activity of the catalysts in the NO, reduction. 

Supported vanadia catalysts and physical mixtures of V2O5 and Ti02 are described, regarding mechanisms and kinetics. Kinetic data for a variety of supported vanadia catalysts are given in Table 5.5 [71]. Catalysts with Ti02 as support have the highest activity. 

One of the most successful industrial applications of polymeric catalytic membranes is the Remedia Catalytic Filter System to destroy toxic gaseous dioxins and furans from stationary industrial combustion sources by converting them into water, CO2, and HCl. The system consists of an expanded polytetrafluoroethylene (PTFE) microporous membrane, needle-punched into a scrim with a catalytically active PTFE felt. The catalyst is a V2O5 on a Ti02 support. The microporous membrane captures the dust but allows gases to pass to the catalyst where they are converted at temperatures as high as 260° C. 

The selective catalytic reduction of NOx with NH3 (NH3-SCR) is used worldwide to remove NOx in the waste gases of power plants [1,2]. V2O5 catalyst supported on Ti02 with WO3 promoter, which has been commercialized more than twenty years ago, still remains as the most effective among a great number of catalysts tested, and it is used in almost all the commercial plants. 

Vanadia SCR catalysts contain V2O5 as the active component. V2O5 is typically impregnated on an anatase Ti02 support together with WO3 to stabilize the vanadia and increase thermal durability. Typical compositions are 1-3 % V2O5 and 10 % WO3 on the Ti02 support [2, 15]. 

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