Transport properties of gas-expanded liquids in bulk and under confinement

Diffusion properties of carbon dioxide-expanded toluene in bulk and confined to nanoporous glasses have been assessed using pulsed field gradient technique of NMR. In the bulk phase the diffusivity of toluene is found to increase significantly with increasing carbon dioxide content. The same dependence is observed in the mesoporous glass with large pore size, but with lower absolute values resulting from the tortuosity of the porous matrix. In contrast, in the porous glass with small pore size, strong confinements lead to different behavior due to an altered equilibrium phase composition in the pore space affecting the mass transfer rates.

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► Diffusivities of CO2-expanded toluene have been directly measured using PFG NMR.
► Diffusion behavior of bulk and confined mixtures are compared.
► Confinement effect upon transport properties of gas-expanded liquids is observed.
► The existence of a composition gradient on the pore length scale is suggested.