Statistical mechanics and molecular simulation of adsorption of ternary gas mixtures in nanoporous materials

We report the results of extensive equilibrium molecular dynamics simulatio n of adsorption of ternary gas mixtures in a class of model nanoporous mate rials, namely, carbon molecular sieve membranes (CMSMs), which are being ut ilized for separation of gas mixtures. We use a novel three-dimensional mol ecular pore network model for CMSMs based on Voronoi tessellation of the si mulation cell. The simulations with such a model allow us to investigate th e effect of the morphology of the pore space, i.e., its pore size distribut ion and pore connectivity, on the adsorption isotherms. We also extend a st atistical mechanical theory of adsorption of single gases and their binary mixtures, recently developed by us, to ternary mixtures and use the results of the molecular simulations to test its accuracy. The theory is shown to provide very accurate predictions for the simulation results over wide rang es of the temperature and porosity of the membrane. The performance of the theory is also compared with that of another theory of adsorption based on a virial expansion. (C) 2001 American Institute of Physics.