CADMIUM-EXCHANGED Y-ZEOLITES STUDIED WITH CARBON-MONOXIDE AND XENON AS PROBES

The adsorption isotherms of carbon monoxide and xenon, as well as the Xe-129 NMR chemical shifts of xenon, in 46 and 68% cadmium-exchanged zeolites NaY have been investigated. The sets of experimental data can be explained quantitatively with a unifying approach which considers localized adsorption of both CO and xenon on well defined adsorption sites consisting of two types of cadmium cations in different environments, and sodium cations. The cadmium cation sites are characterized by their individual adsorption constants for CO and xenon, by their heats of adsorption for CO (49 and 38 kJ mol(-1)) and by the Xe-129 NMR chemical shifts of the xenon atoms accommodated on them (152 and 58 ppm). The concentrations of these sites as a function of the cadmium exchange were determined.