Mirella Musci

Synthesis of ultrafine TiO2 powders by a CW CO2 laser

Abstract A laser-induced process for the synthesis of ultrafine TiO 2 powders has been developed. The work is mainly concerned with the evaluation of the role of the process parameters on production rate and reaction efficiency. The powder characteristics, in particular particle size, crystallinity and composition, have been analyzed through different techniques.

Laser synthesis of vanadium-titanium oxide catalysts

A laser-induced process has been studied and developed for the synthesis either of pure TiO 2 powders for use as a catalyst support or of mixed Ti 1− x V x O 2 oxides to be used directly as catalysts in the selective catalytic reduction of nitrogen oxides with ammonia. The radiation source is a 600 W cw CO 2 laser and the precursors are titanium and vanadium alkoxides whose vapors are carried under the laser beam by controlled flows of an inert gas and of a reaction sensitizer. The study of the process has been mainly devoted to the optimization of the production rate and of the reaction efficiency. The powder characteristics, related to the process parameters, have been investigated through different techniques. The results show that the particles are monodispersed, unaggregated, monocrystalline with anatase structure and their diameters can be as small as 50 A. Vanadium contents up to X = 0.25 have been obtained in Ti 1− x V x O 2 compounds, without V 2 O 5 segregation. Finally, a comparison between the behavior of surface VO x active sites has been carried out in catalysts prepared by chemical impregnation of TiO 2 and in the mixed Ti–V oxide powders.

Vanadium oxide catalysts supported on laser-synthesized titania powders: Characterization and catalytic activity in the selective reduction of nitric oxide

Abstract 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 VIV containing species which prevails up to 6 wt.-% V2O5 and a VV 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 VIV containing species.