A Pt-loaded Y-type zeolite (Pt/NaY) membrane was prepared on the surface of a porous alpha-Al2O3 support tube by hydrothermal synthesis and then ion-exchanged with platinum. The thickness of the zeolite layer and the amount of Pt loaded were ca. 12 mum and 1 wt%, respectively. The membrane was employed in the form of a cylindrical thin catalyst for the selective oxidation of CO in an H-2-rich mixture. A mixture of CO, O-2 and H-2 was fed to the outer surface of the membrane, and CO was selectively oxidized during its permeation through the thin layer. The permeation fluxes for H-2 and CO were determined at 423-523 K. Permeation fluxes also calculated by means of a mathematical model using effective diffusion coefficients and reaction kinetics. The effective diffusion coefficients through the zeolite membrane were estimated from gas permeation test data, obtained at 423-523 K, and the oxidation rates of CO were determined over a particulate catalyst that had the same composition as the Pt/NaY membrane. As a result, the diffusion coefficients of O-2, N-2 and CO were determined to be (0.7-1.0) x 10(-7) m(2) s(-1) at 423-523 K, and the activation energies for the rate constants for CO oxidation were 61-77 kJ mol(-1). The predicted permeation fluxes of H-2 and CO using the mathematical model were in good agreement with the experimental data, when the oxidation selectivity of CO to H-2 was assumed to be 80% in the model calculation. (C) 2003 Elsevier Science Ltd. All rights reserved.