Facile synthesis of ordered mesoporous γ-alumina monoliths via polymerization-based gel-casting

Abstract

Porous γ-alumina monoliths with hexagonal mesoporous structures were prepared starting from well-ordered mesoporous alumina powders which were firstly synthesized by the self-assembly of aluminum isopropoxide and a triblock copolymer in the presence of nitric acid. The alumina powders were fused together to form alumina monoliths by the integration of polymer gel-casting together with the calcination at different temperatures in air. The powdery and monolithic products were investigated using transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), small-angle X-ray scattering (SAXS), powder wide-angle X-ray diffraction (WA-XRD) and the nitrogen adsorption–desorption isotherm measurements. As results, the as-prepared powdery alumina possesses ordered p6 mm hexagonal mesoporosity, high BET surface area and narrow pore-size distribution. After high-temperature calcination, the obtained alumina monoliths still exhibit ordered mesoporosity with hexagonal symmetry, which is very similar to that of the original powdery sample except for the reduced pore volume and specific surface area. The method can be extended to prepare other porous metal oxide monoliths when appropriate powdery metal oxides with a connected pore system are applied.