Atomically detailed simulations of surface resistances to transport of CH4, CF4, and C2H6 through silicalite membranes

We have used atomically detailed methods to examine the surface resistances associated with single-component permeation of CH4, CF4, and C2H6 through single crystal silicalite membranes. Dual control volume grand canonical molecular dynamics (DCV-GCMD) simulations can be used for this purpose, but only for extremely thin membranes and for relatively rapidly diffusing species. We use calculations of this type to introduce a more computationally efficient but approximate method for describing surface resistances, the local equilibrium flux method (LEFM). Using LEFM calculations, it is possible to accurately and rapidly predict surface resistances for large ranges of membrane operating conditions. Using this approach, we identify the crystal thicknesses beyond which surface resistances are negligible for single-component permeation of CH4, CF4, and C2H6 through silicalite membranes as functions of membrane feed and permeate pressure.