Use of a pyrogenically prepared silicon-titanium mixed oxide powder as a catalyst

Use of a pyrogenically prepared silicon-titanium mixed oxide powder which is present in the form of aggregated primary particles, as a catalyst or catalyst support, characterized in that the silicon-titanium mixed oxide powder - a content of TiO SiO wherein the sum of the proportions of TiO - a BET surface area of 30 to 150 m - an anatase of> 80% to 95% based on the sum of rutile and anatase, rutile and the Anatasbereiche of a primary particle are fused together and - having a photon efficiency of at least 1.5%.