Surface properties of aluminium hydroxide gels prepared from pure and mixed aqueous, ethanolic and acetonic media

Abstract

Abstract This work deals with the preparation of aluminium hydroxide gels by precipitation from pure and mixed solvents in the presence of propylamine acting as proton acceptor in the hydrolysis reaction. As solvents were used water, ethanol and 50% v/v water‐ethanol and water‐acetone mixtures. Pure acetone could not be used because the aluminium salt used (AlCl 3 .6H 2 O) was not sufficiently soluble in it. The samples were freeze‐dried and activated to temperatures up to 773 K. The samples prepared from aqueous solutions showed the structure of poorly crystallized pseudoboehmite, while the sample prepared from pure ethanol was nearly amorphous and presented the highest specific surface area of all the samples (570 m 2 g −1 for thermal activation at 473 K). The sample prepared from aqueous acetone exhibited the highest porosity (about 4 cm 3 g −1 ) consisting of pores of nearly uniform size. This porosity remained almost constant throughout the range of thermal activation temperatures.