Infrared Studies on Water Adsorption Systems with the Use of HDO.IINa-Y zeolite

　Infrared spectra of the systems of Na-Y zeolite-H₂O,D₂O,and HDO were measured. It was shown that there are three types of adsorbed water in the zeolite-water system. Type I:adsorbed in a state in which two hydroxyl bonds are highly non-equivalent; it gives absorptions at 3695, 3400, and 1645 cm^-1,and is the same type as that on the Molecular sieve 13X. Type II: adsorbed in another state in which the bonds are nearly equivalent; it gives bands at 3610, 3540, and 1645 cm^-1. Type II was more resistant to dehydration than Type I, and was irreversible for the back-adsorption of a small amount of water at room temperature, whereas Type I was almost completely reversible. Type III was observed for back-adsorption under this condition; it gives bands at 3635, 3500, and 1655 cm^-1.