Studies of the Properties of the Basic Sites on the Silica-alumina Surface through the Reaction of the Basic Sites with Copper(II) Complexes Containing 2,2′-Bipyridine

Abstract

Abstract The substitution reactions of complexes with basic sites on the surfaces of silica-alumina and alumina and the properties of the basic sites were studied through the adsorption of the complexes onto the surfaces. The hydroxyl groups with basic strengths of two kinds, H0>9.3 and 7.2<H0<9.3, exist on the silica-alumina surface pretreated at 300°C. They are present in a cluster state. The basic strength becomes higher as the outgassing temperature becomes lower. The complexes predominantly interact with the O2− ions on the surface pretreated at a relatively high temperature, resulting in new chemical species. The basic strength of the O2− ions is lower than that of the hydroxyl groups on the surface pretreated at a lower temperature. The hydroxyl groups on the alumina surface outgassed at 300°C are distributed, on the whole, homogeneously in comparison with those of the silica-alumina surface, and their basic strength is H0>9.3. The nature of the basic sites on the alumina surface tends to vary with the outgassing temperature, similarly to those on the silica-alumina surface. These analyses were performed on the basis of the ESR spectra for complexes in basic solutions.