Anisotropic Xe Chemical Shifts in Zeolites. The Role of Intra- and Intercrystallite Diffusion

We provide observations and interpretations of 129 Xe chemical shifts in open zeolite networks in which the Xe is in fast exchange among a large number of cavities and channels, in two zeolite types different from the A types that we have used before, and provide quantitative comparisons of adsorption isotherms and average 129 Xe chemical shifts using grand canonical Monte Carlo (GCMC) simulations employing the same methods and shielding functions used previously. We examine the temperature dependence of the Xe chemical shift at a fixed loading in NaY and silicalite and compare the predicted behavior with that of Xe n in the α cages of NaA. Furthermore, we consider the most general case where the chemical shift reported by a Xe atom includes sampling environments in several crystallites and intercrystalline gas during acquisition of the NMR signal.