Evidence of Facilitated Transport in Crowded Nanopores.

Fluid transport in nature often occurs through crowded nanopores, where a number of phenomena can affect it, because of fluid-fluid and fluid-solid interactions, as well as the presence of organic compounds filling the pores and their structural fluctuations. Employing molecular dynamics, we probe here the transport of fluid mixtures (CO2-CH4 and H2S-CH4) through silica nanopores filled with benzene. Both CO2 and H2S are strongly adsorbed within the organic-filled pore, partially displacing benzene. Unexpectedly, CO2/H2S adsorption facilitates CH4 transport. Analysis of the trajectories suggests that both CO2 and H2S act as vehicle-like carriers and might swell benzene, generating preferential transport pathways within the crowded pore. The results are useful for identifying unexpected transport mechanisms and for developing engineering approaches that could lead to storage of CO2 in caprocks.