Steam reforming of methane (SMR) and of other hydrocarbons currently constitutes some of the key reactions for hydrogen production. A mathematical model was developed for investigating several cases, such as: non-isothermal, non-adiabatic and non-isobaric SMR. Our adsorptive reactor model adopts the linear driving force model for solid uptake and extended Langmuir isotherm for adsorption equilibrium. A transient pressure equation is incorporated to account for the variable pressure dynamics. Numerical solutions of model equations for the cyclic process were obtained by orthogonal collocation within the method of lines. The model predictions compared well with experimental data and were validated. The integrated reactor/separator units with variable catalyst/adsorbent distributions were tested for optimal performance. The pressure reaction columns were found to behave as reactor/separators in series. The performances were investigated in terms of conversion, selectivity, hydrogen productivity, and the removal efficiency of CO(2) and CO from the reaction zone. The distributions of catalyst/adsorbent beds in the reactor were found to have significant effects on the overall reactor/separator performance. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.