Membrane reactors can be used to overcome the equilibrium conversion limits of conventional reactors. In this study, a plug flow model has been employed to investigate the performance of a membrane reactor used to carry out the reversible reaction A reversible arrow B. Reactor design parameters and operating condition are presented that yield conversions exceeding the equilibrium conversion. A formula for the conversion at these conditions is also presented. As an application, the n-butane to isobutane isomerization reaction is considered. A 40% improvement in conversion is found to be possible.