Self-diffusion of heptane inside aggregates of porous alumina particles by pulsed field gradient NMR

•Microscopic study of heptane self-diffusion in porous alumina by PFG NMR.•Diffusivities inside crystal aggregates of porous alumina were measured directly.•Intra-aggregate diffusivities were correlated with the structural properties.

1H and 13C pulsed field gradient (PFG) NMR was used to study the self-diffusion of heptane in porous alumina exhibiting a hierarchy of pore sizes that cover the range from micropore to macropore sizes. Diffusion measurements were performed for the lengths scales of displacements comparable with and smaller than the sizes of aggregates of porous alumina particles. The measured heptane diffusivities inside the particle aggregates were found to be several times smaller than the diffusivity in the bulk liquid heptane. The diffusivities inside the aggregates were correlated with the aggregate structural characteristics, which include pore volume, pore size and packing density of the individual particles in the aggregates.

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