Boundary effects of molecular diffusion in nanoporous materials: A pulsed field gradient nuclear magnetic resonance study

A pulsed field gradient nuclear magnetic resonance (NMR) was used to analyze the effects of boundary conditions on the molecular diffusion in nanoporous materials. The scanning electron microscopy (SEM) was used for determining the crystal sizes. Three independent techniques for probing the crystal size were compared by taking advantage of the pecularities of mass transfer at the interface between the zeolite bulk phase and the surrounding atmosphere. The techniques were based on the measurement of effective diffusivity, the application of NMR tracer desorption technique and the analysis of the time dependence of the effective diffusivity in the short-time limit.