Auto-thermal reforming (ATR) is one of the key technologies to produce hydrogen from natural gas. Applying an 112 membrane to an ATR reactor can simplify the process for pure hydrogen production, and in the meantime can promote methane conversion into hydrogen. Although it is a promising approach and has a great potential application in the future, it is still in an early stage of development. The objective of this work is to systematically study the factors affecting the pure hydrogen production and the thermodynamic efficiency of the integrated process containing an H-2-membrane ATR reactor. The study has been accomplished by the simulation of the H-2-membrane ATR reactor and the thermodynamic analysis of the process. The simulation work is based on the kinetics of the reactions and the mechanisms of membrane permeation. The effects of factors including the flowing mode of sweeping gas, the rate of sweeping gas, the inlet rate of CH4, and the inlet ratio of CH4 to H2O, on the production rate of separated H-2, on the driving force of hydrogen permeation, and on the thermodynamic efficiency of the integrated process have been explored. The results will have a significant contribution to the design of an H-2-membrane ATR reactor and an integrated process for pure hydrogen production. (c) 2006 American Institute of Chemical Engineers