Gel-derived porous alumina systems

Highly porous alumina systems were aimed to produce by a low energy-consuming sal-gel technique. Using the newly developed method based on a freeze drying technique, the expensive supercritical extraction can be avoided. Only two materials are needed for the synthesis: an inorganic Al salt and an organic solvent. Basic or chelating agents are not necessary to apply for gelation. The cryogels produced by freeze drying were compared with the aerogels obtained by the supercritical technique. The porous alumina systems have different structures; the aerogels can be characterized with nanopores (10-20 nm) and the cryogels with hierarchical (macro- and meso-)pores (8-16 mu m and 70-80 nm). The cryogel systems keep their high porosity even above 1300 degrees C. (C) 2013 Elsevier B.V. All rights reserved.