LOW-TEMPERATURE (144-K) XE-129 NMR-STUDIES OF ZEOLITES

129Xe nuclear magnetic resonance (NMR) spectra of xenon adsorbed in offretite, silicalite, and L and CaA zeolites have been measured at 144 K. Changes of the chemical shift and line width of the 129Xe resonance as a function of the xenon loading reflect the size of the pores in the zeolites. In zeolites with small pores, the chemical shift increases gradually with loadings, and the resonance is broad, while in zeolites with large pores, the chemical shift undergoes rapid increases in the high loading regime, accompanied by drastic reductions in the line width. These differences in the chemical shift and the line width may be attributed to a gas-liquid phase transition of the adsorbed xenon in zeolites with large pores.