Purification of finely divided, pyrogenically prepared metal oxide particles

A process for removing halide compounds adhering to finely divided metal oxide particles having a BET surface area of from 5 to 600 m2/g with steam, the metal oxide particles being formed by reaction of halide-containing starting materials by hydrolysis or oxidizing gases, wherein

• said finely divided metal oxide particles containing residues of halide compounds are fed, together with reaction gases, to the upper part of an upright column and migrate downwards through the column due to gravity,
• steam having a temperature of from 100° C. to 500° C., optionally mixed with air, is fed to the bottom end of the column,
• the finely divided metal oxide particles containing residues of halide compounds and the steam are fed counter-currently,
• the metal oxide particles freed of halide residues are removed at the base of the column, and
• steam and halide residues are removed at the head of the column,
• which process is characterized in that
• the column is heated in such a mariner that the temperature difference Tbottom−Ttop between the lower part and the upper part of the column is from 50° C. to 100° C., the maximum temperature in the column is in the lower part of the column, the maximum temperature in the column is from 350° C. to 425° C., and the metal oxide particles have a residence time in the column of from 1 second to 30 minutes.