A comprehensive mathematical model has been developed and used to simulate the catalytic dehydrogenation of ethylbenzene to styrene using two types of membrane reactor system, i.e. a composite membrane consisting of a thin but continuous metal membrane film of Pd-Ag alloy deposited on the outside surface of a porous ceramic substrate and a microporous membrane tube with the thin permselective layer on the outside of the tube. Various operating parameters have been considered including the separation layer thickness, porosity, reactor length and contact time. Feed stream compositions were also varied. Superior performance in terms of conversion enhancement far above the equilibrium value was observed for the Pd-Ag composite membrane system and was attributed to its exclusive hydrogen permeability characteristics.