Intracrystalline Diffusion in Zeolites Studied by Neutron Scattering Techniques

Neutron scattering techniques can be used to study the different motions of molecules adsorbed in zeolites: vibrations, rotations and translation. Using combined instruments, it is now possible to measure diffusivities ranging from 10-7 to 10-14 m2s-1. Furthermore, incoherent scattering, using hydrogenated molecules, allows to determine the self-diffusivity; while coherent scattering, studying deuterated molecules, gives access to the transport diffusivity. Several applications of the neutron techniques are described in this review. They are illustrated by the case study of xylenes in X-type zeolites. Other examples are related to alkanes in MFI-type zeolites, n-alkanes in 5A zeolite, and water in X and A-type zeolites