Mathematical models taking into account the non-isothermal condition and radial heat and mass transfer for the dehydrogenation of ethylbenzene to styrene in a conventional fixed-bed reactor and a palladium membrane reactor were developed using the kinetic data of a 70 wt% F2O3:20 wt% K2O:5 wt% Ce2O:5 wt% Cr2O3 catalyst and the H-2 permeation data through a palladium membrane with 10 mum thickness. The study showed that due to the continuous removal of H. from the reaction side, both the conversion and the selectivity obtained from the membrane reactor were superior to those of the conventional fixed-bed reactor. It was shown by the theoretical study that the assumptions of isothermal and plug-flow conditions overestimated the performance of the reactors. The membrane reactor with a catalyst packed in the shell side showed superior performance to the one with a catalyst packed in the tube side because the former had lower heat transfer resistance than the latter. The operating modes in the separation side played an important role in determining the reactor performance. The use of reactive sweep gas did not only rapidly consume the permeating H. but also supplied additional heat to the reaction side; however, the resulting performance may be interior to the other operating modes such as vacuum and inert sweep gas modes.