jp9b07969_si_001.pdf (480.7 kB)
Preferential Adsorption in Ethane/Carbon Dioxide Fluid Mixtures Confined within Silica Nanopores
journal contribution
posted on 2019-12-13, 20:44 authored by M. Dolores Elola, Javier RodriguezMolecular dynamics simulations have been performed to
investigate
the structural and dynamical properties of fluid ethane confined within
cylindrical silica nanopores of 3.8 and 1 nm diameters. Pure ethane
and equimolar mixtures of ethane and CO2 were considered
for the analysis. Computer simulations were carried out along the
supercritical isotherm T = 320 K, exploring densities
within the range ρ/ρc = 0.05–2.28. Density
profiles along the axial and radial directions of the pore, orientational
distribution functions, analysis of interfacial dynamic properties,
and estimations of diffusion coefficients are presented. In agreement
with experimental data, the results show the formation of a dense
adsorption layer, with densities that may be up to 10 times larger
than those of the bulk phase, in particular at low densities and under
subnanometer confinement. The incorporation of CO2 changes
the scenario, leading to preferential adsorption of CO2 over ethane species. The dynamics of ethane also change in mixtures,
in agreement with experimental measurements. These changes are manifested
by increments in the diffusion coefficients of confined ethane in
the presence of CO2. However, in contrast with experimental
data, our results for the diffusion coefficients of confined ethane
showed a monotonic decreasing behavior with increasing bulk density.
Plausible interpretations for this discrepancy are also discussed.