Infrared Studies on Water Adsorption Systems with the Use of HDO. I. Molecular Sieves 13X and 4A

Abstract

Abstract It was shown that the use of HDO molecules in IR studies on water adsorption system is advantageous for obtaining information as to whether 1) a band arises from the surface structural hydroxyl groups or from adsorbed water molecules, 2) a band arises from an overtone bending vibration, and 3) water molecules are adsorbed in a state of its two hydroxyl bonds being equivalent. The bands in the spectra of Molecular sieves–H2O systems were assigned as follows. I) 13X–H2O system. Bands at 3752, 3685, and 3647 cm−1 correspond to surface structural OH, bands at 3697, 3360, and 1650 cm−1 to asymmetrically adsorbed water molecules, band at 3230 cm−1 to overtone bending vibration of the same molecules. The band at 3590 cm−1 was found to arise from some other type of adsorbed water molecules. II) 4A–H2O system. Bands at 3500, 3400, and 1660 cm−1 correspond to symmetrically adsorbed water molecules, band at 3280 cm−1 to overtone bending vibration of the same molecules. Another type of adsorbed water was suggested to be present.