Facile route to synthesize large-mesoporous gamma-alumina by room temperature ionic liquids

Abstract

A large mesoporous gamma-alumina was fabricated through a thermal process without postaddition of molecular or organic solvents at ambient pressure in an open container by using the dual functions of 1-hexadecyl-3-methylimidazolium chloride (C(16)MimCl) as room-temperature ionic liquids (RTILs), i.e., templating and cosolvent functions. In this synthesis, a thermal process with the assistance of RTILs was the key technology for induction of the nanostructure of aluminum hydroxide and transformation to boehmite crystallites by means of intermolecular interaction. Both C(16)MimCl/boehmite hybrid and gamma-alumina displayed the nanostructure consisting of randomly debundled nanofibers embedded in wormlike porous networks. Nanofibers of C(16)MimCl/boehmite hybrid and gamma-alumina exhibited a length of ca. 40-60 nm and a diameter of ca. 1.5-3 nm. In particular, gamma-alumina had good thermal stability and reasonable acidic sites. After conversion from boehmite crystallites into gamma-phase by calcination, this nanostructured gamma-alumina obtained the largest surface area and pore volume among large mesoporous gamma-aluminas around 10 nm pore size, i.e., 470 m(2) g(-1) in surface area, 1.46 cm(3) g(-1) in pore volume, and 9.9 nm in pore size by calcination at 550 degrees C. Therefore, this synthetic method is a facile way to synthesize various nanostructured inorganic materials with the enhanced physical properties.