Design of Hybrid Materials for Gas Separations Using Molecular Simulation

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ABSTRACTProposal Number: CTS-9984621Principal Investigator: David M. FordInstitution: Texas A&M UniversityTitle: Design of Hybrid Materials for Gas Separations Using Molecular SimulationAn emerging class of gas separations, where a dilute species of higher molecular weight must be removed from a light gas stream, is becoming increasingly important due to economic and environmental driving forces. Examples include the removal of volatile organic compounds from air and the removal of higher molecular weight alkanes from natural gas. This project examines a novel hybrid membrane for such separations. The membranes are mesoporous (5 nanometer) ceramics that are surface-derivatized with organic oligomers having desired chemical functionalities. A very useful aspect of these membranes is that free volume and surface chemistry can be modified independently; the former quantity is related to how many oligomer chains are deposited, while the latter is dictated by the chemistry of the chosen oligomer. Both quantities can be varied to obtain optimal characteristics for a particular separation. In addition to experimental synthesis and testing, molecular simulation is being used as a primary tool for advancing the engineering of these hybrid membranes and providing a means for materials design. Membrane processes often provide favorable economic alternatives to traditional gas-separation processes. Process economics dictate that membranes for such separations must be selective for the larger, more dilute components; this type of selectivity is the opposite of the usual "sieving" behavior exploited in most membrane separations. This work explores the synthesis and evaluation of a novel type of membrane created by chemically modifying the surfaces of porous ceramic materials with organic chains. Such treatment creates an environment that is friendly to larger organic compounds and enhances their removal from the gas stream. Such a separation strategy is expected to yield economic and operational advantages in practice.