Gas permeation through nano porous sol-gel derived silica membrane

Templated silica membrane is prepared on α-alumina annular as support by sol-gel polymerization rout, using cationic surfactant, cetyl pyridinium bromide, as template agent. Gas transport mechanisms through porous membranes as well as influences of main parameters in each mechanism have been reviewed individually. Membrane characteristics have been studied, using nitrogen absorption isotherms. The membrane surface morphology and cross sectional views have been presented using electron microscopy. Gas permeation properties through support as macro-porous membrane as well as silica membrane have been studied using experimental set up at the temperature range of 25-200 ^deg^C and pressure range of 1-2 bar. Permeation through α-alumina support increased with mean pressure and decreased with rising the temperature and results showed good agreement with viscous flow model, whereas permeation on silica templated membrane increased with temperature and showed no dependency with the mean pressure and followed configurational model. Values of perm selectivity in binary mixtures of H₂/CH₄, H₂/C0₂ and CO₂/CH₄ were nearly pressure independent and very close to the values of separation factor, while both values were significantly higher than the Knudsen selectivities. Permeation measurements and membrane characterization were also carried out with pure silica membrane (with no template agent); also using polymerization rout and comparison between the two silica membranes have been done. It was found that the characteristics of the membrane as well as gas permeation properties are so affected by using template agent in preparation of the sol-gel silica membranes. Permeation of hydrogen and methane through the templated membrane were approximately twice of those for the non-templated membrane, while in the case of carbon dioxide it was vice versa; permeation of carbon dioxide increased in the nontemplated membrane. The increase of permeation for hydrogen is due to the larger pore size of the templated membrane in comparison to the non-templated membrane. For methane in addition, this is due to more tendency of adsorption of methane on the templated membrane surface. Increase of carbon dioxide permeation through non-templated membrane is related to the control of permeation more from the molecular size (d_CO2CH4)