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

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 degreesC were 30 nanometers in thickness, showed a H2 permeance at 200 degreesC 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 degreesC showed no detectable CH4 flux, with a H2 permeance of 5 x 10(-7) (mol m-2 s-1 Pa-1) at 200 degreesC. 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.