Surface probing of synthetic faujasites by adsorption of carbon dioxide. Part 1.—Infra-red study of carbon dioxide adsorbed on Na-Ca-Y and Na-Mg-Y zeolites

Abstract

Infra-red spectroscopy of carbon dioxide adsorbed on Na-Ca(Mg)-Y faujasites is used to determine the distribution of Ca and Mg ions over the cation sites. Physisorption of CO₂ provides a sensitive method for the detection of Ca²⁺ and Mg²⁺ in supercage positions. High temperature outgassing of the samples facilitates the migration of bivalent ions from positions in the supercage to the small cavities. Bivalent ions in the dehydrated Y samples are only present in the supercages when the degree of ion exchange is 46 to 48% or higher. For high temperature chemisorption of CO₂, the chemisorbed species are closely related to co-ordinated carbonate ions. The concentration of this species does not exceed 2 molecules per unit cell.