Silicon-titanium mixed-oxide prepared by flame hydrolysis and having a surface enriched in silicon dioxide, its production and use thereof

Silica-hydrolytically produced silicon-titanium mixed oxide powder with a weight ratio of silicon dioxide / titanium dioxide which is greater on the surface of the primary particles than in the total primary particle. It is prepared by a flame hydrolysis method by separating a stream of a vaporous titania precursor and oxygen or an oxygen-containing gas and hydrogen and a second stream of a vaporous silica precursor and a carrier gas of oxygen, an oxygen-containing gas and / or an inert gas the reaction chamber of a burner, as it is known for the production of pyrogenic oxides, leads and burns there, then cools the solid mixed oxide powder and hot gases and separates the gases from the solid.