INVESTIGATIONS OF ADSORBED ORGANIC-MOLECULES IN NA-Y ZEOLITE BY XE-129 NMR

The adsorption of n-hexane, benzene, and trimethylbenzene in Na-Y zeolite supercages has been investigated by use of xenon-129 NMR. As shown by J. Fraissard and co-workers, xenon-129 is an excellent probe of its environment in zeolites and is sensitive to the number of adsorbed guest molecules. The xenon-129 chemical shift, when extrapolated to zero effective xenon pressure, is 89.7 ± 0.1 ppm for benzene, 89.0 ± 1.3 ppm for trimethylbenzene, and 107.7 ± 1.2 ppm for n-hexane at a concentration of two guest molecules per zeolite supercage compared to 58.9 ± 0.5 ppm for empty Na-Y zeolite supercages. This approach is useful for determining the number of adsorbed molecules inside zeolite supercages and gives information about their arrangement within the supercages.