(653g) Study of Permeation and Separation through Mesoporous Membranes Using Dynamic Mean Field Theory

Mesoporous membranes find application in multicomponent vapor phase separations such as removal of carbon dioxide from flue gas and recovery of volatile organic compounds (VOCs) from light gas streams through preferential adsorption and condensation of one of the species.  However, design rules for mesoporous materials pertaining to specific separations are still unclear. Selectivity and permeance of membranes is determined by surface and capillary effects resulting from mesopore characteristics (geometry, surface chemistry) but truly predictive correlations for these effects based on mesoporous attributes are absent. In this work permeation through mesopores has been modeled using Dynamic Mean Field Theory (DMFT), a coarse grained lattice based density functional theory. DMFT has been applied to two types of membrane experiment: permporometry, which represents permeation of a light gas through a mesopore in presence of a condensable vapor at a controlled relative pressure, and VOC recovery, where the goal is to enrich condensable VOC, present in a stream of light gas at low concentration, through application of pressure gradient. DMFT predicts fluxes and selectivity, and provides deep insight on transport mechanisms. Interestingly, in simple slit or cylindrical pores, most of the light component flux was observed to be associated with the layer adjacent to the strongly adsorbed surface layer of the heavy component. Different pore geometries, and the influence of microporosity in the material structure (as in SBA-15), have also been studied.