The Effects of Temperature on Particle Size in the Gas-Phase Production of TiO2

Ultraflne titanium dioxide powder was synthesized by the gas-phase oxidation of titanium tetrachloride in a multistage aerosol reactor. The reactor consisted of three zones: an evaporation zone for TiCl₄, a preheating zone for oxygen and vaporized titanium tetrachloride, and a reaction zone. Preheating temperature of reactants, partial pressure of reactants, and temperature in the reaction zone were chosen as experimental variables for the control of particle size and distribution. Ultratine TiO₂ powders ranging from 30 to 70 nm in average particle sizes were produced. The preheating temperature of reactants was found to be an effective factor for particle size and distribution of ultraflne powders. As the preheating temperature was increased, average particle size became smaller and size distribution more uniform. Larger particles having narrow size distributions were produced with an increase in TiCl₄ mole fraction under the control of preheating temperature. However, variation of O₂ mole fraction did not show much difference on the average particle size. As the temperature in the reaction zone was increased, average particle size became smaller. With the decrease in the residence time of reactants in the reaction zone smaller particles were obtained.