Guest Diffusion in Binderless High‐Performance NaX Molecular Sieves

Abstract

The pulsed field gradient (PFG) NMR technique is applied for exploring the diffusion behavior of guest molecules in binderless NaX beads in comparison with the zeolite powder employed for their production. With both probe molecules applied (water, n-hexane), the diffusivities in the powder and the beads are found to essentially coincide as long as the diffusion path lengths are sufficiently small in comparison with the extension of the individual particles (crystallites) of the powder. With increasing diffusion path lengths, characteristic deviations become observable that can be attributed to the differences in long-range mass transfer through the intercrystalline void volume of the bed of crystallites and within the individual beads of the binderless molecular sieve, respectively. With these studies, PFG NMR demonstrates its potentials for simultaneously recording mass transfer phenomena in both the micro-and macropores of commercially produced binderless molecular sieves.

Pulsed field gradient NMR diffusion measurement in nanoporous materials

“…As an example, Fig. 9 shows the PFG NMR signal attenuation observed with n-hexane in a binderfree granule of zeolite NaY [134], where the individual crystallites are mutually connected by bridges of a genuine NaYtype crystalline phase [155][156][157][158].…”