(756b) Trade-Off between Selectivities and Permeabilities in Planar Anisotropic Membranes for Gas Separations

To date the design of membranes for gas separations has mainly relied on the use of isotropic materials. In isotropic membranes separation occurs as a result of differences in flux magnitude of the species involved. Recently, we have introduced an alternative approach for the design of membrane materials by considering engineered anisotropic membranes. In anisotropic membranes separation occurs as a result of controlling both the magnitude and the direction of flux. A fundamental physical consequence of controlling the flux direction is the development of spatially dependent permeabilities and selectivities. In this talk we discuss the capabilities and performance advantages of anisotropic membranes in a simple planar configuration. We show how anisotropic materials can be used to improve the separation ability of current membranes, pushing the limits of existing technologies. We discuss the possibility of increasing the selectivity of membrane separations via flux directional control and also the existence of a trade-off between selectivity, permeability and the collected fraction of the permeate. Our findings on anisotropic planar membranes are applied to the separation of binary mixtures of O₂/N₂ and H₂/CH₄.