Hydrogen separation from a syngas mixture with different compositions was studied by using a Pd-Ag membrane. The effect of temperature (from 300 degrees C to 600 degrees C) and of relative pressure (from 0.2 MPa to 0.5 MPa) was studied. In general, rises of both these parameters allowed increasing H-2 permeate flux. The Pd-Ag membrane showed to have a great selectivity, as when inlet gas mixture contained different compositions of CO2, CO or CH4, these gases were never detected in membrane permeate side. However, when hydrogen content in inlet gas decreased, a significant reduction in H-2 permeate flux was observed, especially when CO was present, probably due to the deposition of solid carbon in membrane surface by Boudouard reaction. It was also observed the formation of hydrocarbons, due to CO and H-2 reactions. H-2 permeances were calculated by application of Sieverts' law and values between 4.9 x 10 (4) and 1.5 x 10 (3) mol m (2) s (1) Pa (0.5) were obtained. The highest value was obtained at 600 degrees C. H-2 permeances at different temperature followed Arrhenius' equation. Thus, activation energies values between 11.5 kJ mol (1) and 14.0 kJ mol (1) were calculated. (C) 2012 Elsevier Ltd. All rights reserved.