A yttria-stabilized zirconia (YSZ, 8 mol Y 2O 3) membrane was prepared employing zirconium n-propoxide as a precursor via sol�gel method. Unlike conventional methods, hydrolyzing water was slowly released in this method through esterification of 1-propanol and glacial acetic acid. X-ray diffraction verified that YSZ membrane was partially transformed to the tetragonal phase. Ten times dip-coated membrane thickness was about 742 nm, determined by field emission scanning electron microscopy (FE-SEM) micrograph. Brunauer�Emmet�Teller measured average pore size of unsupported YSZ from gas adsorption and desorption indicating two modes centered at 2.66 and 2.38 nm. Crystallite size (D) as calculated from Scherrer�s equation was 6.8, 12.23, and 13.61 nm for unsupported YSZ powder before and after calcination, respectively, at 25, 500, and 600�C. Thermogravimetric analysis showed that the mass loss of the samples calcined at temperatures higher than 600�C had no significant differences indicating the completion of loss of organics. Supported YSZ membrane was tested by a gas permeation apparatus. The single gas permeance of YSZ membrane including α - Al 2O 3 was measured as 14.89 � 10 - 6 and 1.75�10-6molm-2s-1Pa-1 for H 2 and CO 2 at 300�C, respectively. Permeance of H 2 and CO 2 through YSZ in 75:25 H 2/CO 2 binary feed mixture was 9.696 � 10 - 6 and 0.97�10-6molm-2s-1Pa-1, respectively, at 300�C. The selectivity of hydrogen in YSZ was 10. It was concluded that the membrane was highly promising for the separation of H 2/ CO 2 mixture from various H 2-containing process streams under steam environment for high-temperature separation. © 2016, King Fahd University of Petroleum & Minerals.