In this paper, typical and Pd-Ag membrane methanol loop reactors have been analyzed. in the proposed models all basic equipments in the methanol loop were included. Detailed dynamic models described by set of ordinary differential and algebraic equations were developed to predict the behavior of the overall processes. The conventional model was validated against plant data, and then the results of the hydrogen-permselective membrane loop are compared with the conventional model. Using this novel model, diffusion by membrane tubes compensates reduction of production rate due to catalyst deactivation. By use of the membrane model, dynamic optimization of temperatures was performed for improving overall methanol production. Here, differential evolution (DE) method was applied as powerful method for optimization of procedure. optimal inlet temperatures of membrane tube, steam drum and both of them were determined. The optimization approaches enhanced additional yield throughout 4 years of operation as catalyst lifetime. Therefore, the methanol synthesis loop can be deduced to redesign based on this study. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.