The capture of small mole fractions of SF6 in N2 gas into long and short carbon nanotubes CNT (11,11) – simulation studies

This study discusses the selective adsorption and diffusion of pure SF6 and N2 gases as well as their gas-mixture, in particular at very low SF6-concentrations, in equilibrium with carbon nanotubes CNT(11,11) through molecular simulations. These CNTs demonstrate remarkable separation capabilities with an adsorption selectivity up to a factor of more than 4000. We investigate both infinitely long tubes and short tube fragments, thus also exploring boundary effects. The examination of short fragments represents, to our knowledge, a novel contribution. The reason for the pronounced selectivity is to be found mostly in the difference between the enthalpy of adsorption of SF6 and N2. Geometric considerations of the molecules are of secondary significance. Conclusions concerning realistically low mole fractions of SF6 are drawn.