Patent ID: 7718261

Claim:
A process for the production of the composition comprising nanoscale pyrogenically produced zinc oxide powder wherein zinc powder is converted to zinc oxide powder in four successive reaction zones, wherein the four successive reaction zones are an evaporation zone, a nucleation zone, an oxidation zone and a quench zone, whereby in the evaporation zone the zinc powder conveyed there by an inert gas stream is evaporated in a flame of air and/or oxygen and a fuel gas, under the proviso that the reaction parameters are chosen such that oxidation of the zinc does not occur, to provide a hot reaction mixture consisting of zinc vapor, water vapor as a reaction product of forming the flame and, optionally, excess fuel gas, and whereby in the nucleation zone, the hot reaction mixture arrives from the evaporation zone, and cools to temperatures below the boiling point of zinc or is cooled to temperatures below the boiling point of zinc by means of an inert gas, thereby forming zinc crystallites, and whereby in the oxidation zone the mixture from the nucleation zone is oxidized with air and/or oxygen, and whereby in the quench zone the oxidation mixture is cooled to temperatures of below 400° C. by addition of cooling gas; wherein the zinc oxide powder is separated from the gas stream.