Abstract
Highly porous aerogels and xerogels of Cr(III)-Fe(III) bulk mixed oxides with high surface areas were prepared from their nitrate precursors using propylene oxide as a gelation promoter. Products obtained upon treating the gels under supercritical conditions of the employed solvent were compared with their counterparts obtained from gels treated with supercritical CO2 to remove the solvent. Solvent supercritical conditions resulted in amorphous or weakly crystalline nanopowders, after calcination at 500 degrees C, with significantly higher surface areas and larger pore volumes. Furthermore, the mixed oxides showed enhanced reducibility than their parent single metal oxides which was reflected in an enhanced catalytic activity in the oxidation of benzene. Besides their dependence on the preparative conditions, physicochemical properties and catalytic activity of the composites were significantly dependent on the Fe/Cr ratio. (C) 2015 Elsevier B.V. All rights reserved.