Y-type zeolite membranes were prepared on porous support tubes by hydrothermal synthesis, and then ion exchanged using Pt, Ru, Rh, Co, Ni, Cu or Ag (referred to as PtY, RuY, RhY, CoY, NiY, CuY and AgY membranes, respectively). The permeances to H-2 and CO through the NaY membrane at 373-523 K were (8.3-9.6) x 10(-7) and (4.6-5.3) x 10(-7) mol m(-2) Pa-1 s(-1), respectively. The permeances of the other membranes did not differ significantly from those of the NaY membrane. The metal-loaded Y-type zeolite membranes were then used for the selective oxidation of CO in an H-2-rich mixture (H-2:CO2:CO = 89:10:1 on a molar basis). The permeation fluxes of CO for the COY, NiY and AgY membranes were not affected by the addition of O-2. For the case of the PtY, RuY, CuY and RhY membranes, however, the permeation fluxes of CO decreased with increasing O-2 concentration, when a small amount of O-2 was added to the feed. This suggests that these membranes had activity for the CO oxidation. The PtY membrane was the most highly active under the conditions used. (C) 2002 Elsevier Science Inc. All rights reserved.