Simultaneous dimethyl ether synthesis and decalin dehydrogenation in an optimized thermally coupled dual membrane reactor

Abstract

The efficient coupling of exothermic and endothermic reactions in a membrane reactor reduces the size of reactors and operational costs, improves thermal efficiency and also increases the production rate in the processes. In the present study, a thermally coupled dual-membrane reactor for simultaneous production of hydrogen, dimethyl ether (DME) and naphthalene is proposed. In this configuration, the exothermic DME synthesis reaction is coupled with the endothermic dehydrogenation of decalin to improve the heat transfer between the endothermic and exothermic sides. Furthermore, in order to increase the production rate, a Pd/Ag membrane and a hydroxy sodalite (H-SOD) membrane are assisted for separation of pure hydrogen from the endothermic side and permeation of water from the exothermic side respectively. The operating conditions of thermally coupled dual-membrane reactor are optimized via differential evolution (DE) method to maximize outlet DME mole fraction in the exothermic side as well as outlet hydrogen mole fraction in the endothermic side. Then a comparison is made between the optimized thermally coupled dual-membrane reactor (OTCDMR), the optimized thermally coupled reactor (OTCR) and conventional DME synthesis reactor (CR). The outlet DME mole fraction increases about 34.2% and 3.42% in OTCDMR and optimized thermally coupled reactor respectively, compared with conventional one. Hydrogen mole fraction in the outlet point of OTCDMR also improves about 6.4% in comparison with the one in optimized thermally coupled reactor. In addition to the enhancement of hydrogen and DME mole fractions, a more favorable profile of temperature is achieved in OTCDMR compared with other reactors.