A model and the simulation of a membrane reactor for xylene isomerization are presented. Kinetic parameters :for the reaction carried out under industrial conditions are optimized using plant data with a conventional plug-flow model. In the membrane reactor, the characteristics of a ZSM-5 film supported on porous SS tubes, which was developed in our laboratory, are included to simulate the improvement in p-xylene production at 370 degrees C. The values used for the simulations correspond to ternary mixtures at 370 degrees C, and they are: 430 x 10(-8), 8.44 x 10(-9) and 8.45 x 10(-9) mol s(-1) m(-2) Pa-1 for p-, o- and m-xylene, respectively. In this vein, while for the output of the conventional plug-flow reactor the ratio p-/o-/m-xylene is 1.000/0.936/1.940, in the case of the membrane reactor the rate is improved to 1.000/0.830/1.719, taking into consideration the contribution of the permeate and retentate sides. Consequently, an increase of 12% in p-xylene production is predicted by increasing permeation area and sweep gas flow, restricted to a reasonable pressure drop and whithin the physical and constructive feasibility of the SS tubes. (c) 2006 Elsevier B.V. All rights reserved.