Hydrogen is considered today as a promising fuel of the future in order to address the existing environmental concerns associated with the use of fossil fuels. Hydrogen PEM fuel cells are an important enabling technology for this purpose, but their operating temperature is typically low and, as a result, common impurities found in conventional hydrogen production like CO, can adsorb on and poison the catalysts utilized. Therefore, high-purity hydrogen is required for the operation of such systems. In this study a realistic size, ultra-permeable Pd membrane is used for pure hydrogen production from a feed with a simulated reformate composition through the water gas shift (WGS) reaction. Prior to its use in the reactor experiments, the membrane is characterized through single-gas permeation measurements. The effect of feed pressure and flow rate and sweep ratio on membrane performance during the WGS experiments is experimentally studied, and the results are compared with those of a mathematical model. The model is further used to study the design aspects of the process. It is shown that the Pd membrane reactor system under study is capable of attaining almost complete CO conversion and full hydrogen recovery at realistic experimental conditions akin to those utilized in industrial applications. (C) 2011 Elsevier B. V. All rights reserved.