Computer simulation was used to study the effects of surface heterogeneity upon gas permeation through slit-like carbon membranes by using the novel technique of μVT ensemble non-equilibrium molecular dynamics. Energetically heterogeneous surfaces were prepared by randomly removing a number of carbons from the first layer of graphite basal planes. Methane and ethane were used as model gases for pure- and mixed-gas permeation. A small heterogeneity on the pore surface was found to result in a large decrease in the permeation flux, due to an increase in the frequency of molecular collisions onto heterogeneous sites. The densities in equilibrium with feed gases decreased almost linearly with an increase in the surface heterogeneity, but the decrease was not as large as that in permeation flux. In the case of the permeation of a binary mixture, permoselectivity of the more adsorptive substance (ethane) was found to change only slightly with an increase in the surface heterogeneity.

Effects of Surface Heterogeneity on Gas Permeation through Slit-Like Carbon Membranes by Non-Equilibrium Molecular Dynamics Simulations. Furukawa, S.I., Hayashi, K., Nitta, T.: Journal of Chemical Engineering of Japan, 1997, 30[6], 1107-12