Mathematical simulation and optimization of methanol dehydration and cyclohexane dehydrogenation in a thermally coupled dual-membrane reactor

Thermally coupling of endothermic and exothermic reactions in a membrane reactor improves thermal efficiency and production rate in the processes, reduces the size of reactors and decreases purification cost. This paper focuses on modeling and optimization of a thermally coupled dual-membrane reactor for simultaneous production of hydrogen, dimethyl ether (DME) and benzene. A steady state heterogeneous mathematical model is developed to predict the performance of this novel configuration. The catalytic methanol dehydration reaction takes place in the exothermic side that supplies the necessary heat for the catalytic dehydrogenation of cyclohexane to benzene in the endothermic side. Selective permeation of hydrogen and water vapor through the Pd/Ag and composite membranes are achieved by co-current flow of sweep gas through the membrane wall. The differential evolution method is applied to optimize the thermally coupled dual-membrane reactor considering the summation of DME and benzene mole fractions from reaction sides and hydrogen mole fraction in the permeation side as the main objectives. The optimization results are compared with corresponding predictions for an industrial methanol dehydration adiabatic reactor operated at the same feed conditions. Methanol conversion enhances about 5.5% in the optimized thermally coupled dual-membrane reactor relative to the conventional DME reactor. The results suggest that coupling of these reactions in the proposed configuration could be feasible and beneficial.