REACTIVITY OF V2O5-WO3 TIO2 CATALYSTS IN THE SELECTIVE CATALYTIC REDUCTION OF NITRIC-OXIDE BY AMMONIA/

The physico-chemical characteristics and the reactivity of sub-monolay er V2O5-WO3/TiO2 deNO(x) catalysts is investigated in this work by EPR , FT-IR and reactivity tests under transient conditions. EPR indicates that tetravalent vanadium ions both in magnetically isolated form and in clustered, magnetically interacting form are present over the TiO2 surface. The presence of tungsten oxide stabilizes the surface V-IV a nd modifies the redox properties of V2O5/TiO2 samples. Ammonia adsorbs on the catalysts surface in the form of molecularly coordinated speci es and of ammonium ions. Upon heating, activation of ammonia via an am ide species is apparent. V2O5-WO3/TiO2 catalysts exhibits higher activ ity than the binary V2O5/TIO2 and WO3/TiO2 reference sample. This is r elated to both higher redox properties and higher surface acidity of t he ternary catalysts, Results suggest that the catalyst redox properti es control the reactivity of the samples at low temperatures whereas t he surface acidity plays an important role in the adsorption and activ ation of ammonia at high temperatures.