Patent 305 801

In the present invention, there is disclosed a process for preparing a photocatalycally active material, ammonium peroxotitanate in the form of a foam of very low packing density in the range of 1 to 10 g.dme-3 and titanium oxide, which maintains the morphological structure of thwe ammonium peroxotitanate, such that hydrated titanium oxide, obtained by the dissolution of the precursor in water and subsequent precipitation thereof with a basic precipitation agent, is treated in the aqueous suspension with hydrogen peroxide to yield a yellow transparent gel, which is further lyophilized at a temperature lower than 0 degC to -64 degC and water vapor pressure corresponding to the appropriate temperature until removal of all water phase to obtain the ammonium peroxotitanate foam, whereby the amount of the precursor in the aqueous solution is in the range of 1 to 25 percent by weight. In such a manner yellow very porous foam is formed, wherein the texture thereof is particularly dependant on the concentration of the titanium oxide in the colloidal solution of the packing density in the range of 1 to 10 g.dme-3. So prepared yellow foam can than preferably be annealed to a temperature in the range of 450 to 1100 degC, wherein the texture of the starting peroxotitanate gel remains maintained.