Acidity of bimetallic silica composites prepared by a complexing agent assisted sol-gel method

Acidity of amorphous sol-gel aluminum silicates containing transition metals was investigated by using FT-IR spectroscopy. The composites were prepared from metal alkoxides using diols as complexing agent. The samples were characterized by XRD, SEM, TEM, thermal analysis and BET surface measurement. Pyridine was used as probe molecule for the IR acidity measurements. H-2 treatment enhances the amount of both Bronsted and Lewis acid sites in Al-containing samples, but has no significant effect on pure silica matrices. Lewis acidity is primarily determined by the type and amount of transition metals incorporated into the composite. (C) 1999 Elsevier Science B.V. All rights reserved.