Preparation of alumina gels by a non-hydrolytic sol-gel processing method

Abstract

Monolithic alumina gels were prepared by a novel non-hydrolytic sol-gel route based on the condensation reaction between aluminum alkoxides Al(OR)3 and aluminum halides AlX3, through the formation of alkyl halide RX(X = Br, Cl; R = iso-propyl, sec- or ter-butyl), around 100°C. Samples were then calcined and were found to be amorphous up to about 750°C; they kept a high specific surface area to about 900°C. This delayed crystallization is correlated with the large number of five-coordinate aluminum sites measured in dried gels by 27Al NMR spectroscopy.