Permeation properties and microstructure of porous inorganic membranes.

Microstructures of porous inorganic membranes and permeation properties through those membranes were reviewed for amorphous silica membranes and zeolite membranes. Silica membranes were compared by the permeation properties of hydrogen such as activation energies or selectivities over nitrogen or helium. The activation energies of hydrogen through silica membranes prepared by the sol-gel method and the CVD method were the same level, and relatively loose or dense structure can be made by both methods. The effects of intercrystalline pathways on the permeation properties through zeolitic membranes were investigated. The intercrystalline pathways were filled by coking of a hydrocarbon or counterdiffusion CVD method. The permeation properties through intercrystalline pathways were explained by an i-i model. According to this model, ethanol was permselective from ethanol aqueous solution through intercrystalline pathways of the MFI zeolite membrane.