This paper provides an experimental and modelling analysis of the performance of a membrane reactor with separate feed of reactants for the combustion of methane. In this reactor concept methane and air streams are fed at opposite sides of a Pt/gamma-Al2O3-activated porous membrane which hosts their reaction. The effect of a number of operating parameters (temperature, methane feed concentration, pressure difference applied over the membrane, type and amount of catalyst deposited, time of operation) over the attainable conversion was assessed, while measuring any possible slip of unconverted methane to the air-feed side. The maximum specific heat power load which could be attained with the most active membrane in the absence of methane slip was approximately 15 kW m(-2) with virtually no NOx emissions. Such potential might perhaps be exceeded if a properly designed membrane is tailored on purpose. For this sake a model, based on differential heat and mass balances throughout the membrane thickness, proved to be a promising design tool, since it allowed proper accordance with the experimental data with a single fitting parameter (pre-exponential kinetic constant). (C) 2000 Elsevier Science S.A. All rights reserved.