Deuterium solid-state NMR study of the dynamics of molecules sorbed by zeolites

The dynamics of small organic molecules sorbed by zeolite molecular sieves has been investigated by using solid-state deuterium NMR. The systems studied include methanol, benzene, toluene, and p-xylene sorbed by zeolites ZSM-5, mordenite, Y, and erionite. The dynamics of uptake or filling of the zeolite void volume has been observed. Intracrystalline molecular motion has been observed and used to characterize the molecular sieve effect. For example, a preferred diffusion of p-xylene in the straight channels of ZSM-5 has been observed, which tends to support the theory of molecular traffic control. The physical state of physisorbed species is described in the light of the deuterium NMR results. The behavior of sorbed molecules is characterized as that of surface-adsorbed species. The effects of site-selective adsorption and diffusion on the state of sorbed species is described