The goals of this research are to prepare ultrathin inorganic membranes that are both highly selective and have fluxes that are at least an order of magnitude higher than fluxes of previously reported membranes. These membranes will be prepared by molecular layer deposition (MLD) onto high-flux supports. MLD uses two self-limiting half reactions in sequence to form inorganic-organic hybrid layers, which are then oxidized to remove the organic layer and create a porous membrane. Membranes prepared by MLD can be less than 10-nm thick because MLD conformally coats surfaces. Both oxide and nitride structures of various compositions will be prepared in order to obtain selective membranes that are hydrothermally stable. These membranes will be used to separate H2/CO2 and H2/CO mixtures at high pressures and temperatures since such conditions are more demanding tests of membrane quality and better represent separations applications. This project takes advantage of recent observations that a thin MLD alumina layer on a SAPO-34 zeolite membrane increased the H2/N2 separation selectivity almost two orders of magnitude, and these membranes were selective up to at least 1.5 MPa pressure. The successful completion of this project will result in the ability to design inorganic oxide and nitride membranes with high fluxes and high selectivities. Because the MLD layers are so thin (10 nm or less), fluxes will be high, and such membranes would be potentially transformative for membrane separations.
Broader Impacts
Preparation of ultrathin membranes that have dramatically higher fluxes and high selectivities for H2 separations could have a major impact on H2 utilization by significantly reducing the cost of these separations. Most inorganic membranes are at least two orders of magnitude thicker than 10-nm, and preparing ultrathin membranes that are almost defect free would be a major advance in membrane science. MLD provides a new approach to prepare a novel class of membranes that have the potential for broad application. Understanding how to control the pore size of ultrathin membranes prepared by MLD also opens up the potential for many applications that require separating mixtures with small differences in the size of molecules (e.g., O2/N2, CO2/N2). High flux membranes with high selectivities would have a significant impact on energy utilization because traditional separations are such energy-intensive processes. The PI has successfully patented results of his research with the potential to rapidly and directly benefit society through commercialization. This proposed project will directly impact one PhD student, at least four undergraduate students, and at least two high school students. Screencasts will be prepared on membrane separations and on MLD and posted on www.LearnChemE.com to disseminate information about MLD and membranes.
