In this study, a bench-scale Pd membrane reactor was used to carry out the methane steam reforming reaction under realistic operating conditions: 580 degrees C, 28 bar(a) and GHSV values up to 950 h(-1). The continuous withdrawal of the H-2 product resulted in a maximum CH4 conversion of 98% and a H-2 production rate of 0.13 N m(3) h(-1). A continuous methane conversion of 86% and a hydrogen flux of 0.1 mol m(-2) s(-1) were achieved in the membrane reactor under these challenging conditions for almost 1100 h, demonstrating the great potential of membrane reformers for H-2 production. (c) 2012 Elsevier B.V. All rights reserved.