Anodic alumina supported dual-layer microporous silica membranes

We present a new processing scheme for the deposition of microporous, sol-gel derived silica membranes on inexpensive, commercially available anodic alumina (Anodisk (TM)) supports. In a first step, a surfactant-templated mesoporous silica sublayer (pore size 2-6 nm) is deposited on the Anodisk support by dip-coating, in order to provide a smooth transition from the pore size of the support (20 or 100 nm) to that of the membrane (3-4 angstrom). Subsequently, the microporous gas separation membrane layer is deposited by spin-coating, resulting in a defect-free dual-layer micro/mesoporous silica membrane exhibiting high permeance and high selectivity for size selective gas separations. For example, in the case of CO2:N-2 separation, the CO2 permeance reached 3.0 MPU (1 MpU = 10(-7) Mol m(-2) s(-1) Pa-1) coupled with a CO2:N-2 separation factor in excess of 80 at 25 degrees C. This processing scheme can be utilized for laboratory-scale development of other types of microporous or dense inorganic membranes, taking advantage of the availability, low cost and low permeation resistance of anodic alumina (or other metal oxide) meso- and macroporous supports. (c) 2006 Elsevier B.V. All rights reserved.