Perturbation of OH groups in decationated Y-zeolites by physically adsorbed gases. Part 2.—Heats of adsorption

Abstract

The shift and the change in intensity of the OH high frequency stretching band of a decationated near faujasite Y-zeolite have been correlated to the heats of physical adsorption of Ar, Kr, O₂ and CH₄. The initial isosteric heats of adsorption of these gases decrease with increasing polarizabilities of the adsorbates. This unusual behaviour is tentatively explained by assuming that the potential energy of adsorption involves an additional positive term corresponding to the increase of the OH dipole moment. The reaction field arising from the change of the dielectric constant in the zeolitic cavity should be responsible for this increase. This simple electrostatic model allows one to correlate the infra-red to the thermodynamic data.