Hydrogen permeation through a palladium disk membrane (5 mm in diameter and 50 mu m in thickness) was investigated in the presence of steam, methane, propane and propylene. Co-existing methane and propane had a negligible effect on hydrogen permeation. When propylene was fed with hydrogen, however, the permeance was greatly decreased, and the extent of deactivation increased with time. Hydrogen permeation was independent of the carbon concentration in the membrane, and a carbonaceous matter, which was formed by the decomposition of propylene was the major origin of the deactivation. The addition of steam decreased the hydrogen permeation rate for the hydrogen-methane and hydrogen-propane mixtures but attenuated the decrease in the hydrogen permeation rate for the hydrogen-propylene mixture. The carbonaceous matter which was chemisorbed to the membrane could be gradually removed by treatment with hydrogen at 600 degrees C, and the hydrogen permeation rate was recovered to 80% of the initial value after a week of treatment time. Regeneration using oxygen at 600 degrees C was effective in removing the carbonaceous matter, and the permeation rate was fully recovered within 15 min. (C) 2000 Elsevier Science B.V. All rights reserved.