Preparation of γ-alumina large grain particles with large specific surface area via polyol synthesis

We developed the polyol synthesis of γ-alumina particles that allows for control of their particle size from the nanometer level to the micrometer level. The developed polyol synthesis utilized a reflux reaction of ethylene glycol solution with aluminum nitrate hexahydrate and poly(vinylpyrrolidone) (PVP). Two important process parameters - the molecular weight of PVP and refluxing temperature - were investigated to control the size of the alumina particles. Further, two growth models for amorphous alumina particles in polyol synthesis were suggested. γ-Alumina with secondary particle size ranging from 142 nm to 1.0 μm with a specific surface area ranging from 81 to 32 m2/g was obtained. The α-alumina prepared by high-temperature annealing of over 1200 °C had secondary particle sizes ranging from 246 to 330 nm, but with specific surface areas of only 5.4-11 m2/g. Therefore, it is proved that the polyol synthesis is able to control secondary particle size of γ-alumina upon maintaining a large specific surface area.