Synthesis of mesoporous γ-alumina nanorods using a double surfactant system by reverse microemulsion process

Abstract

Mesoporous γ-Al₂O₃ nanorods were synthesized by a reverse microemulsion (water in oil, w/o) technique using an aqueous-based alumina sol, the anionic surfactant AOT (sodium bis(2-ethylhexyl sulfosuccinate)), the non-ionic co-surfactant Span 80 (sorbitan monooleate) and cyclohexane as an organic solvent. The γ-Al₂O₃ phase was obtained at 500 °C with a slight transformation to θ-Al₂O₃ at 700 °C–900 °C, while a mixed phase of γ-, θ- and α-Al₂O₃ resulted at 1000 °C. The BET surface area, pore volume and average pore size of the 500 °C-treated sample was found to be 59.3 m² g⁻¹, 0.040 cm³ g⁻¹ and 2.65 nm respectively, which changed slightly in the temperature range of 500 °C–900 °C. The mesoporous γ-alumina nanorods were formed through rod-like micelle formation in the presence of surfactant/co-surfactant in organic solvent, which was illustrated by a proposed mechanism.