VANADIUM-OXIDE CATALYSTS SUPPORTED ON LASER-SYNTHESIZED TITANIA POWDERS - CHARACTERIZATION AND CATALYTIC ACTIVITY IN THE SELECTIVE REDUCTION OF NITRIC-OXIDE

Laser-activated pyrolysis was applied to the synthesis of ultrafine TiO2, producing a non porous monocrystalline material in anatase phase with high specific surface area and uniform particle size. This powder was used as support for the preparation of vanadia catalysts with different compositions by wet impregnation. The pure TiO2 and the vanadia catalysts were characterized by X-ray diffraction, transmission electron microscopy, Fourier transform IR, X-ray photoelectron spectroscopy, ammonia temperature-programmed desorption and were tested in the reaction of nitric oxide reduction by ammonia. It has been proposed that two different VOx species formed in the submonolayer region: a V(IV) containing species which prevails up to 6 wt.-% V2O5 and a V(V) containing species which develops from 6 wt.-% V2O5 up to monolayer completion. The structure of these species has been hypothesized. A reaction scheme has been proposed to interpret the catalytic activity for the selective catalytic reduction (SCR) of NOx. The selectivity of catalysts for nitrogen is related to the prevalence of the V(IV) containing species.