Inorganic oxide aerosols of controlled submicronic dimensions

Abstract

Metallic oxides aerosols are prepared by decomposition of anhydrous chlorides in the diffusion flame of a hydrogen–oxygen reactor. The flow rate of the chloride vapour, the temperature of the flame and the residence time of the reagent in the flame determine the shape (spherical or polyhedral), the dimensions (in the range from 60 Å to 2000 Å) and in some cases the crystalline structure of the particles, which in all cases are non-porous.

These highly divided oxides exhibit unusual photocatalytic properties which are not encountered with aerosols in the micron range or with porous particles prepared in a conventional way. Titanium dioxide, in particular, enables the catalytic photo-oxidation (in the u.-v. range) at room temperature of organic and inorganic compounds. Paraffins and olefins are oxidized partially and/or totally whereas ammonia yields N₂O and N₂, carbon monoxide yields carbon dioxide and hydrogen sulphide yields sulphur dioxide and sulphur.