A Grand Canonical Monte-Carlo Study of Lennard-Jones Mixtures in Slit Pores; 2: Mixtures of Two Centre Ethane with Methane

Mixtures of ethane and methane in a slit micropore were simulated using the Grand Canonical Monte Carlo technique. Ethane was modelled as two Lennard-Jones sites while methane was modelled as a single Lennard-Jones site. The elongated shape of ethane was found to strongly influence the calculated adsorption selectivity, and important qualitative differences were noted relative to an earlier GCMC study (Cracknell et al., Molec Phys Vol 80, pp 885–897, 1993) in which ethane was modelled as a spherical Lennard-Jones particle. The influence of ethane bond length on methane-ethane selectivity was studied further by conducting simulations with the ethane C[sbnd]C distance 28% and then 70% longer than its actual length; the hindrance of rotation by confinement in the micropore was found to cause a significant decrease in selectivity. The Ideal Adsorbed Solution Theory was found to predict the selectivities with a reasonable degree of accuracy given simulated single component data as input.