A yttria-stabilized zirconia (YSZ) membrane was formed on the surface of a porous a-alumina support tube by a sol-gel procedure. The membrane was then impregnated with an aqueous solution Of H2PtCl6 or RhCl3 center dot 3H(2)O and calcined in air at 500 degrees C, to produce a Pt- or Rh-loaded YSZ membrane. Methane steam reforming (MSR) over the Rh-loaded Ce0.15Zr0.85O2 catalyst was carried out in a membrane reactor using the Pt-loaded YSZ membrane. Methane conversion in the membrane reactor was 20% higher than that in a packed bed reactor due to the high permeation rate of hydrogen compared to the reaction rate. In addition, Pt- and Rh-loaded YSZ membranes were also examined for the selective oxidation of CO from a mixture of H(2)and CO without any packed catalysts. When 02 was added to the feed, CO was oxidized in the Pt-loaded YSZ layer and the CO concentration of 10,000 ppm. on the feed side was decreased to below 30 ppm (detection limit) at 150 degrees C. Meanwhile the oxidation of CO was suppressed at higher temperatures because of the consumption of O-2 as a result of the catalytic oxidation of H-2. (c) 2004 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.