The ethanol steam reforming reaction has been performed in a membrane reactor consisting of a Pd-Ag tube (wall thickness 150 mu m) filled with a Ru-based catalyst. The experiments have permitted to characterize the Pd-Ag permeator in terms of both hydrogen permeability and yield of the steam reforming reaction at temperature of 400 and 450 degrees C in the pressure range 100-800 kPa. The permeation tests exhibited hydrogen permeability values in agreement with the literature and the complete hydrogen selectivity. In the reaction tests, water/ethanol mixtures of molar ratio 10/1 and flow rates of 5, 10 and 15 g h(-1) have been fed in the lumen side of the membrane tube while the permeated hydrogen has been collected in the shell side by a nitrogen sweep stream. At 450 inverted perpendicular C with a reaction pressure of about 400 kPa and a water/ethanol feed flow rate of 5 g h(-1,) maximum values of hydrogen yield (5.5) and hydrogen recovery factor (close to 100) have been measured. The hydrogen yield reduces at lower temperatures and pressures as well as when larger water/ethanol flow rates are fed (10 and 15 g h(-1)). Finally, a simulation code based on a simplified reaction kinetics has been developed: the comparison with the results of the tests permitted to determine the parameters of such a kinetics. A model analysis of the membrane reformer aimed at verifying the influence of the main operating parameters has been carried out, too. (C) 2011 Elsevier B.V. All rights reserved.