Separation properties of a mordenite membrane for water-methanol-hydrogen mixtures were studied in the temperature range from 423 to 523 K under pressurized conditions. The mordenite membrane was prepared on the outer surface of a porous alumina tubular support by a secondary-growth method. It was found that water was selectively permeated through the membrane. The separation factor of water/hydrogen and water/methanol were 49-156 and 73-101, respectively. Even when only hydrogen was fed at 0.5 MPa, its permeance was as low as 10(-9) mol m(-2) s(-1) Pa-1 up to 493 K, possibly suggesting that water pre-adsorbed in the micropores of mordenite hindered the permeation of hydrogen. The hydrogen permeance dramatically increased to 6.5 x 10(-7) mol m(-2) s(-1) Pa-1 at 503 K and reached to 1.4 x 10(-6) mol m(-2) s(-1) Pa-1 at 523 K because of the formation of cracks in the membrane. However, the membrane was thermally stabilized in the presence of steam and/or methanol. (C) 2007 Elsevier B.V. All rights reserved.