A GRAND-CANONICAL MONTE-CARLO STUDY OF LENNARD-JONES MIXTURES IN SLITPORES .2. MIXTURES OF 2 CENTER ETHANE WITH METHANE

Mixtures of ethane and methane in a slit micropore were simulated usin g the Grand Canonical Monte Carlo technique. Ethane was modelled as tw o Lennard-Jones sites while methane was modelled as a single Lennard-J ones site. The elongated shape of ethane was found to strongly influen ce the calculated adsorption selectivity, and important qualitative di fferences were noted relative to an earlier GCMC study (Cracknell et a l., Molec Phys Vol 80, pp 885-897, 1993) in which ethane was modelled as a spherical Lennard-Jones particle. The influence of ethane bond le ngth on methane-ethane selectivity was studied further by conducting s imulations with the ethane C-C distance 28% and then 70% longer than i ts actual length; the hindrance of rotation by confinement in the micr opore was found to cause a significant decrease in selectivity. The Id eal Adsorbed Solution Theory was found to predict the selectivities wi th a reasonable degree of accuracy given simulated single component da ta as input.