Differential Evolution Strategy for Optimization of Hydrogen Production via Coupling of Methylcyclohexane Dehydrogenation Reaction and Methanol Synthesis Process in a Thermally Coupled Double Membrane Reactor

The present paper focuses on optimization of a thermally coupled double membrane methanol reactor (TCDMR). This novel configuration is used in order to increase methanol production and achieve pure hydrogen. To reach this goal, the exothermic methanol synthesis reaction is coupled with endothermic dehydrogenation of methylcyclohexane to improve the heat transfer between the endothermic and exothermic sides. Methylcyclohexane (MCH) has been proposed as a potential candidate among the cycloalkanes to produce gaseous hydrogen and a liquid aromatic product toluene (TOL). Two different membrane layers are assisted in TCDMR to improve mass transfer between the exothermic/endothermic side and both permeation sides. A Pd/Ag membrane is used for separation of pure hydrogen from the endothermic side and a hydroxy sodalite (H-SOD) membrane is used for permeation of water from the exothermic side. It has been shown that in situ water removal from the exothermic side has certain advantages. H2O removal improves the activity and selectivity control of the methanol synthesis as well as inhibits the catalyst recrystallization. A steady state heterogeneous model predicts the performance of this innovative configuration. The optimization results have been compared with corresponding predictions for a conventional methanol reactor, thermally coupled methanol reactor, and thermally coupled double membrane reactor. The differential evolution (DE) is a simple and efficient global optimization algorithm applied to optimize the thermally coupled double membrane reactor considering the summation of methanol, toluene, and H-2 recovery yields as the objective function. The simulation results demonstrate that lower water production rate in the optimized TCDMR (OTCDMR) caused 13.8% enhancement in methanol yield in comparison with a conventional reactor and the hydrogen recovery permeation side reaches 2.15 yields.