Porous oxide membranes of γ-alumina, zirconia and silica were prepared on porous α-alumina tubes by sol-gel processes. γ-Alumina and zirconia membranes impregnated with platinum were also prepared. The permeation properties of these membranes were investigated by using unary and binary feeds of H₂ and CO₂ at 423 K. After permeation for 5 h with humidification at a concentration of 3 mol%, no large changes were found for the zirconia and γ-alumina membranes, but the permeances to H₂ and CO₂ for the silica membrane were decreased by 10-20%. A 70-h exposure to humidified feeds showed that the zirconia- and γ-alumina-based membranes were more resistant than the silica membrane. The decrease in H₂ permeance was only 5% for the zirconia-based membranes and 17.4% for the silica membrane. The Pt-loaded γ-alumina membrane remained defect-free after one-month of exposure to the humidified feeds at 423 K.