Effect of SiO2 addition on thermal stability of mesoporous γ-alumina composed of nanocrystallites

The one-pot synthesis of mesoporous γ-Al2O3 via an evaporation-induced self-assembly (EISA) pathway associated with a nonionic block copolymer is described without and with the addition of Si atoms. The resultant γ-Al2O3 possesses a mesostructure comprising an assembly of nano-sized rectangular γ-Al2O3 crystallites of ca. 5 nm in size. Mesoporous γ-Al2O3 prepared without Si addition becomes thermally unstable upon calcination at 1000 °C, with a significant loss of surface area and broadening of pore-size distribution. The addition of Si atoms maintains the mesoporosity of γ-Al2O3 at an elevated temperature through inhibition of the phase transformation of γ- into α-Al2O3 followed by particle growth among the crystallites. The resultant mesoporous γ-Al2O3 with 8.39 mol% of Si has a BET surface area of 263 m2/g at 1000 °C with a narrow pore-size distribution and a mean pore diameter of 8.3 nm.