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

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.