Accelerated crystallization of mesoporous Al2O3 powder recovered by spray-drying with a large amount of heated air

Abstract

The crystallization of inorganic oxide framework in mesoporous materials is a general issue for every application field. An amount of heated air to recover mesoporous Al₂O₃ powders using a spray dryer has made a significant difference in the crystallization behavior into an α-Al₂O₃ phase in addition to the variation in their pore diameter. The crystallization into α-Al₂O₃ at 850 °C was accelerated with mesoporous Al₂O₃ powder prepared with Pluronic F127 recovered from a large amount of heated air. In contrast, the powder recovered from a small amount of heated air resulted in only γ-Al₂O₃ at the same calcination temperature, even though they were recovered from the same precursor solution. Further investigation with other amphiphilic organic templates with varying hydrophilicity and less hydrophilic Pluronic P123 resulted in more accelerated crystallization into α-Al₂O₃; however, the formation of α-Al₂O₃ was not detected with hydrophilic Pluronic F68. Solvent evaporation from the precursor solution was rapidly completed with a large amount of heated air and a less hydrophilic amphiphilic organic template. Therefore, the annealing of the as-recovered mesoporous Al₂O₃ powder was prolonged to accelerate the subsequent crystallization into α-Al₂O₃ at 850 °C.