Preparation in a hydrogen-oxygen flame of ultrafine metal oxide particles. Oxidative properties toward hydrocarbons in the presence of ultraviolet radiation

Abstract

Divided metal oxides (Al 2O 3, Fe 2O 3, GeO 2, SiO 2, TiO 2, V 2O 5, ZrO 2) are prepared by carrying vapor of metal chloride into the flame of an oxygen-hydrogen burner. Collected oxide particles do not have internal porosity and exhibit a nearly constant diameter in the range of 100–2000 Å. The geometry of these particles and their crystalline structure depend on the flame temperature, the flow rate of carrier gas, and the linear velocity of the chloride vapor in the burner. Binary, ternary, or doped oxides may also be prepared by this method from the appropriate mixture of metal chlorides. Oxygen at 25°C is adsorbed on some oxides, in particular on TiO 2, in the presence of uv radiation, as a labile species O 2 − which reacts with paraffins, olefins, CO, SO 2, and NO, under irradiation, to give products of partial or total oxidation. The registered quantum yield is equal to one for wavelengths not exceeding 3400 Å. The reactivity of O 2 − species toward isobutane is investigated by ESR for different wavelengths.