Molecular simulation of the structure of, and transport and separation of gaseous mixtures in carbon molecular sieve membranes

Non-equilibrium molecular dynamics (NEMD) simulation has been performed to study the transport and separation of gaseous mixtures through a single carbon nanopore under practical conditions, i.e., in the presence of a realistic external chemical potential gradient. The effect of pore size, temperature, feed mixture composition, pore wall structure, pore length and gas molecular structure on the transport and separation properties has been investigated. The simulation results are in good qualitative agreement with the experimental data generated in our laboratory with the CMSMs prepared by the carbonization of two polymeric precursors, either Polyfurfuryl alcohol or Polyetherimides.; We have also carried out the first NEMD simulation to study the transport and separation of binary gas mixtures through CMSMs with interconnected pores of distributed sizes modeled by a novel three-dimensional disordered molecular network of interconnected pores consisting of tens of thousands of atoms, based on a Voronoi tessellation of space. Novel results are presented for transport and adsorption of the gases, including the existence of an optimal pore structure for maximum separation of the gases.; A new statistical mechanical theory of adsorption for ternary gas mixtures has also been developed. Extensive results of molecular dynamics simulation of adsorption of single, binary and ternary gas mixtures in CMSMs are presented and used to test the accuracy of the adsorption theory. The theory is shown to provide very accurate predictions for the simulation results in CMSMs over a wide range of the porosity of the porous materials. The performance of the theory is also compared with that of another theory of adsorption based on a virial expansion.