a1 CISE Tecnologie Innovative, POB 12081, Milano, Italy
a2 ENEL-CRTN, Via A. Pisano 120, Pisa, Italy
A laser-induced process has been studied and developed for the synthesis either of pure TiO2 powders for use as a catalyst support or of mixed Ti1−xVxO2 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 CO2 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 Ti1−xVxO2 compounds, without V2O5 segregation. Finally, a comparison between the behavior of surface VOx active sites has been carried out in catalysts prepared by chemical impregnation of TiO2 and in the mixed Ti–V oxide powders.
(Received January 08 1992)
(Accepted June 17 1992)