Synthesis of Porous Inorganic Membranes

Introduction Here we will attempt a brief overview of recent synthetic efforts for micropore and lower-end mesopore membranes. We will not address the very important classes of nonporous membranes, such as dense metals and solid electrolytes with applications in H2 and O2 separations, or mesoand macroporous mem­ branes, which find applications in food processing and water treatment. Micro­ porous materials provide high permselectivities for molecules encountered in the chemical-processing industry but suffer from low intrinsic permeabilities. Therefore, in order to bring microporous membrane materials to commercial ap­ plications, functional composites with small effective thicknesses (in the micron or submicron ränge) must be developed. For example, to achieve economical membrane-reactorsizes, fluxes as high as 0.1 mol/(m s) are desirable. Approaches to microporous membranes include modification of mesoporous membranes by sol-gel and chemical-vapor-deposition (CVD) techniques, carbonization of polymers to form molecular-sieve carbon, and polycrystalline-film growth of zeolites and other molecular sieves.