The role of the intermolecular potential on the dynamics of C ₂H ₄ confined in cylindrical nanopores

The influence of the intermolecular potential on the dynamical behavior of C ₂H ₄, in a bulk phase, and confined inside a (16,0) single-walled carbon nanotubes. The effect of confinement on the self-diffusion coefficient of ethylene was dependent on the particular potential model employed. As C ₂H ₄ is confined, differences between molecular potentials are enhanced resulting in discrepancies in the observed self-diffusivities. When using AA-OPLS model as benchmark, the effect of coarse-graining (CG) was unpredictable, and an appropriate and accurate parameterization may reproduce self-diffusion data. The existence of explicit electrostatic details in the potential seemed to induce short-range order in the confined fluid, resulting in a slowing down of molecular mobility. From the Arrhenius fits, regardless of its own specificities and degree of molecular detail, the activation energy decreased monotonically with increasing molecular density. Because molecules in the dense fluid were highly packed, with little free volume between them, exchange of momentum via molecular collisions was highly efficient, thus significantly increasing the self-diffusional process. This is an abstract of a paper presented at the 2012 AIChE Spring National Meeting and 8th Global Congress on Process Safety (Houston, TX 4/1-5/2012).