A two-dimensional model has been used to simulate the oxidative dehydrogenation of butane on a two-layer catalytic membrane (diffusion layer and V/MgO active layer) operating with segregated reactant feeds. The model considers plug flow on both sides of the membrane, uses an extended Fick's law expression to describe multi-component diffusion in the radial direction, and a complex kinetic scheme to account for the reaction network. The simulation study shows that different feed configurations lead to marked differences on the partial pressure profiles of the different species across the membrane, and explains the performance order (in terms of the selectivity-conversion behaviour) that was observed experimentally. Similarly, the behaviour observed for membranes with catalytic layers of different width was justified by taking into account the variation of the oxygen partial pressure across the active zone of the membrane. 2002 Published by Elsevier Science Ltd.