Organic “template” approach to molecular sieving silica membranes

Abstract

We demonstrate a “template” approach to prepare microporous inorganic membranes exhibiting high flux combined with high selectivity, overcoming limitations inherent to both conventional inorganic (sol-gel, CVD) and organic membrane approaches. Hybrid organic-inorganic polymers prepared by co-polymerization of tetraethoxysilane (TEOS) and methyltrie-thoxysilane (MTES) were deposited on commercial asymmetric alumina supports. Heat treatments were employed to densify the inorganic matrix and pyrolyze the methyl ligands, creating a continous network of micropores. Resulting membranes exhibited very high CO 2 permeance values (2.57×10 −3 cm 3/cm 2 s cm Hg) combined with moderate CO 2 CH 4 selectivities (12.2). Subsequent derivatization of the pore surfaces with monomeric TEOS significantly increased CO 2 CH 4 separation factors (71.5) with only a modest reduction in CO 2 permeance (2.04×10 −4 cm 3/cm 2 s cm Hg). Combined CO 2 CH 4 selectivity factors and CO 2 fluxes exceeded those of all known organic membranes.