Study of acid sites in zeolites by IR spectroscopy in diffuse scattered light. I. Hydroxyl groups in decationized zeolites

Groups of decationized X, Y, and L zeolites and mordenite have been studied by IR spectroscopy in diffuse scattered light in a spectral range which includes fundamental vibrations, overtones, and combination vibrations. It has been concluded that the combination frequencies of the stretching and deformation vibrations are considerably more strongly subject to the influence of the local environment of the ''bridging'' hydroxyl groups than are the stretching vibrations. It has been postulated that the observed differences in the combination frequencies for zeolites of different types are caused by the changes in the degree of coordination of the hydroxyl oxygen atom with the neighboring aluminum atom. The shape of the potential curves of the OH groups in the zeolites has been analyzed, and the parameters characterizing it ν/sub e/, x/sub e/, and D0 have been calculated. The isotope effect accompanying the replacement of the hydroxyl hydrogen atom by deuterium has been discussed