CVD modification and vapor/gas separation properties of nanoporous alumina membranes

A sol-gel derived 4nm pore γ-Al₂O₃ layer, supported on a macroporous α-Al₂O₃ support, was modified by chemical vapor deposition (CVD), with alternative introduction of trimethylaluminum and water vapor into the reaction chamber. Aluminum oxide was deposited in the pores of the γ-Al₂O₃ membrane layer. The modification resulted in a substantial reduction in the permeance of non-condensable gases, but not of condensable vapor. Separation of the mixture of condensable vapor (water) and non-condensable gas (oxygen) was performed on the unmodified and modified membranes at room temperature. The CVD modified membrane exhibits a water/oxygen separation factor as high as 71 at 12% relative humidity with water vapor permeance of 6.9x10^-7mol/m²sPa. In comparison, the maximum separation factor for the unmodified membranes was about 11 at 80% relative humidity with a water vapor permeance of 2.9x10^-7mol/m²sPa. Copyright (C) 1999 Elsevier Science B.V.