A mathematical model of a membrane reactor used for methane steam reforming was developed to simulate and compare the maximum yields and operating conditions in the reactor with that in a conventional fixed bed reactor. Results show that the membrane reactor resents higher methane conversion yield and can be operated under milder conditions than the fixed bed reactor, and that membrane thickness is the most important construction parameter for membrane reactor success. Control of the H-2:CO ratio is possible in the membrane reactor making this technology more suitable for production of syngas to be used in gas-to-liquid processes (GTL). (c) 2005 Elsevier Ltd. All rights reserved.