Alumina-Precursor Nanoparticles Prepared by Partial Hydrolysis of AlCl3 Vapor in Tubular Flow Reactor: Effect of Hydrolysis Conditions on Particle Size Distribution

Aluminum chloride (AlCl3) was evaporated and partially hydrolyzed in water vapor at 300–700 °C in a tubular reactor, 2.4 cm in diameter and 50 cm in length, to form alumina-precursor particles that were more spherical and less agglomerated compared with the fumed alumina produced by flame hydrolysis and oxidation. This study was focused on the effects of the H2O to AlCl3 molar ratio, the reactor temperature, the AlCl3 concentration, and the contact point of AlCl3 with H2O vapors on the morphology, size, and chemical composition of the obtained particles. The primary particle size ranged from 50 to 200 nm depending upon the operating conditions. The particle size increased with increasing AlCl3 concentration but decreased with increasing reactor temperature or with increasing molar ratio of H2O to AlCl3. The particle size became smaller and the particle size distribution narrower as the contact point of AlCl3 with H2O vapors was moved from the inlet of the reactor to a point 10 cm inward toward the center ...