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The adsorption of benzene on dehydrated NaX (Si/Al=1.23) and NaY (Si/Al=2.49, 2.70) zeolites has been studied directly by 1 H and 13 C NMR measurements of the adsorbed benzene and probed indirectly by the combination of 129 Xe NMR and isotherm measurements of the coadsorbed xenon. Powders zeolite samples with varied adsorbate concentrations were investigated. Detailed macroscopic and microscopic adsorption phenomena of benzenc on faujasite-type zeolites, including the loading capacity, mobility, and sites of adsorption, are presented in terms of measurements of NMR line widths and chemical shifts

The adsorption behavior of benzene on dehydrated NaY zeolite has been studied by means of 129Xe n.m.r. and isotherm measurements of adsorbed xenon followed by proton and 13C n.m.r. of adsorbed benzene. Samples with varied benzene loadings were investigated. We found that to obtain a homogeneous molecular distribution in the zeolite cavities, thermal pretreatment of the sample at temperatures above 250°C for a period of several hours was necessary. The maximum number of benzene molecules that can be loaded within a zeolite supercage is found to lie between 4.9 and 5.2. 129Xe n.m.r. has provided valuable information about the arrangement and mobility of adsorbed benzene. To confirm the effect of heat treatment on benzene distribution within NaY supercages, we also examined the proton and 13C n.m.r. spectra of adsorbed benzene and compared them with published results.

The thermal stability of zeolite beta has been studied by 129Xe NMR and adsorption isotherm of adsorbed xenon in correlation with data from X-ray diffraction and 27Al magic-angle-spinning NMR experiments. Samples subject to different calcination and dehydration conditions were examined. Minor destruction of the crystalline framework resulting from dealumination processes has been found for samples treated at a temperature as small as 400°C. At higher temperatures, a severe process of dealumination involving the breaking of 12-membered rings leads to the conclusion that the maximum regeneration temperature of zeofite beta lies near 760°C.