Patent ID: 7235224

Claim:
A process for preparing fine metal oxide particles, comprising the following steps: a) reacting a reactant mixture comprising i) water, ii) at least one water-soluble metal nitrate and iii) ammonia or ammonium salt at a reaction temperature of 250 to 700° C. under a reaction pressure of 180 to 550 bar for 0.01 sec to 10 mm in a reaction zone to synthesize the metal oxide particles, the metal nitrate being contained at an amount of 0.01–20 wt % in the reactant mixture; and b) separating and recovering the metal oxide particles from the resulting reaction products, wherein the ammonia or ammonium salt is contained in the reactant mixture at a molar ratio of 0.5 to 3.0 relative to nitric acid produced from the metal nitrate by the metal oxide synthesis.