(677a) Molecular Simulation of Adsorption and Separation of Pure Noble Gases and Noble Gas Mixtures on Single Wall Carbon Nanotubes

Grand Canonical Monte Carlo simulations were performed to systematically study the adsorption and separation of noble gases on single wall carbon nanotube (SWCNT) bundles. Pure noble gases, as well as binary and ternary mixtures, were simulated in carbon nanotube systems under various conditions. Adsorption data was collected at 100 K and 300 K over a wide range of pressures. Carbon nanotube bundles present distinct adsorption capacities towards different noble gases. In particular, larger and heavier noble gases are easier to be adsorbed at low pressure, while lighter atoms with smaller sizes can be better stored at high pressure. For noble gas mixtures with equal molar loadings, selective adsorption was observed and the selectivity inverted at different pressure ranges according to the choice of mixtures. Furthermore, the influence of loading proportion of the components on the adsorption behavior was investigated by varying the loading partial pressure in binary mixtures from 1% to 99%. Adsorption selectivity was only affected in sub-saturation conditions and no obvious difference in adsorption amount was observed once saturation was reached. The results suggest gas-CNT interactions dominate the adsorption selectivity at unsaturated conditions, whereas the entropic effect plays a more important role after saturation.