(593f) Synthesis And Properties Of High-Silica Sodalite And Deca-Dodecasil 3R Membranes Grown On a-Alumina Supports
Sodalite[1-3] and Deca-dodecasil 3R (DD3R) [4, 5] are promising membrane materials for hydrogen separation from larger gas molecules due to their 6-membered ring (0.28nm) and 8-membered ring pore (0.36×0.44 nm), respectively. The high-silica sodalite (SOD) membranes and deca-dodecasil 3R (DD3R) membranes were hydrothermally synthesized on porous a-alumina supports using tetramethylammonium hydroxide (TMAOH) and 1-adamantanamine (1-ADA) as the structure-directing agents (SDAs), respectively, by in-situ crystallization and seeded secondary growth methods. The XRD and SEM techniques were applied to investigate the phase composition and microstructure of the membranes and corresponding bulk phases. The H2, N2, CO2, and SF6 single gas permeances and their permselectivity of membranes were measured from 25oC to 600oC under different transmembrane pressures. The dependence of gas permeances on the temperature and the transmembrane pressure was investigated and the template removal behaviors of high-silica sodalite and DD3R were studied. For high-silica sodalite membranes, gas permeation studies showed the presence of small micropores after template removal. For DD3R membranes, the CO2/H2 permselectivity declined with increasing temperature and membranes became H2 selective at above 100oC because of the favorable adsorption for CO2 as compared to H2. H2/N2 permselectivity was about 9.0 at 25oC which is much higher than the corresponding Knudsen selectivity (~3.7) and CO2 has higher permeance than N2 at studied temperatures. It was shown that the permselectivities of the seeded membranes were greater than those of the unseeded membranes. It was revealed that the good quality DD3R membranes possessed molecular sieving function for gas separation. It was further demonstrated that repeated hydrothermal treatments improved the quality of these membranes.
Acknowledgements The financial support from Ohio Coal Development Office (OCDO) is gratefully acknowledged.
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