Xe-129 NMR of adsorbed xenon and H-1 NMR imaging: New methods to study the diffusion of gaseous hydrocarbons in a fixed bed of zeolite

Xe-129 NMR of adsorbed xenon used as a probe and H-1 NMR imaging have been used to study the diffusion of hydrocarbons (benzene, n-hexane, paraxylene) during their adsorption or desorption in a fixed bed of zeolite crystallites. The simulation of experimental Xe-129 spectra using the nonuniform or the shrinking core models gives the concentration profiles of hydrocarbons, in the bed and in the zeolite crystallites, during their adsorption and leads to intracrystalline diffusion coefficients in good agreement with the literature. The H-1 NMR imaging allows one to visualize the progression of the diffusing molecules in the zeolite bed and also to determine their intracrystalline diffusion coefficients in the simplest cases.