Membrane reactors provide exciting opportunities for overcoming thermodynamic limits on the maximum attainable conversion of reversible reactions. Some of them are of particular interest to the petrochemical industry. A simple membrane reactor model has been employed to investigate the performance of a reversible reaction A reversible arrow B and identify the operating conditions (for efficient reactant use and reduced waste generation) at which maximum conversion occurs. This conversion supremization problem is shown to be nonconvex and possess discontinuity properties which lead to different optimal conditions. Analytic formulas that describe the maximum attainable conversion have been derived. These help identify when conversions above the equilibrium conversion can be attained. They also reveal that the surface-to-volume ratio should be small to attain maximum conversion. Applications are discussed for butane isomerization reactions important to the manufacture of alkylates and reformulated gasoline.