Probing mass transfer in mesoporous faujasite-type zeolite nanosheet assemblies

Abstract

Pulsed field gradient nuclear magnetic resonance (NMR) diffusion studies are performed by using cyclohexane to probe transport properties in a NaX-type zeolite with a hierarchical pore structure (house-of-cards-like assemblies of mesoporous nanosheets), which is compared with a purely microporous sample. With guest loadings chosen to ensure saturation of the micropores, and the meso- and macropores left essentially unoccupied, guest diffusion is shown to be enhanced by almost one order of magnitude, even at room temperature. Diffusivity enhancement is further increased with increasing temperature, which may, therefore, be unambiguously attributed to the contribution of mass transfer in the meso- and macropores. Diffusion enhancement in pore-space hierarchies: Pulsed field gradient NMR spectroscopy is applied for probing mass transfer in zeolite NaX samples, which are formed as house-of-cards-like assemblies of mesoporous nanosheets. The intraparticle diffusivity of cyclohexane at room temperature is found to exceed that in the purely microporous sample by one order of magnitude, indicating greater enhancement with increasing temperature. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.