Adsorption of Butenes on NaY and Dehydroxylated Y Zeolites Studies by Infrared Spectroscopy

Abstract

Butene molecules adsorbed on NaY and dehydroxylated Y zeolites are bonded to electrophilic acid sites (Na+ ions or Lewis-acid sites) by their π electrons. The interaction of butene molecules with Lewis-acid sites results in an increase in the extinction coefficient of the band for the antisymmetric stretching vibration of the CH3 group thus indicating an increased polarization of the C—H bond. The rates of desorption of the butenes from NaY or dehydroxylated zeolites increase in the sequence but-1-ene < cis-but-2-ene < trans-but-2-ene. These differences are explained by considering the steric factor. At low pressures the maximum butene content in Y zeolites is 3 molecules per supercage.