Permeation of methanol vapor through silica membranes prepared by the CVD method with the aid of evacuation

Silica membranes were prepared by depositing silica on porous glass tubes with the aid of evacuation using tetraethoxysilane as a reactant in the temperature range 673-773 K. The basic permeation properties of methanol vapor in gas phase were investigated. This membrane appears to hinder permeation of methanol vapor. This behavior is quite different from the original porous glass and other reported membranes. The separation factors of He/CH3OH were 7.1 at 373 K and 16.9 at 473 K. These values are much higher than the Knudsen value (He/CH3OH=2.8). The permeances of He and N-2 through this membrane were also measured for varying temperatures in order to investigate the permeation mechanism. Gas permeation through the membrane was predominantly governed by an activated diffusion mechanism. (C) 1999 Elsevier Science B.V. All rights reserved.