High-Selectivity, High-Flux Silica Membranes for Gas Separation

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Process improvements in silica membrane fabrication, especially the use of clean-room techniques, resulted in silica membranes without detectable mesoscopic defects, resulting in significantly improved transport properties. Supported membranes calcined at 400[degree sign]C were 30 nanometers in thickness, showed a H2 permeance at 200[degree sign]C of 2 x 10-6 moles per square meter per second per Pascal (mol m (-2) s-1 Pa-1), and had a CH4 permeance more than 500 times smaller. Molecules larger than CH4 were completely blocked. Silica membranes calcined at 600[degree sign]C showed no detectable CH4 flux, with a H2 permeance of 5 x 10-7 (mol m-2 s-1 Pa (-1)) at 200[degree sign]C. These results signify an important step toward the industrial application of these membranes such as purification of H2 and natural gas as well as the selective removal of CO2.

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