Performance enhancement of thermally coupling of methanol synthesis, DME synthesis and cyclohexane dehydrogenation processes: Employment of water and hydrogen perm-selective membranes via different recycle streams

•Hydroxy sodalite (H-SOD) and Pd/Ag membranes have been employed.•Different recycle stream cases have been studied for the performance of TDCTMR.•A steady state heterogeneous catalytic reaction model is applied to analyze.•The results of TDCTMR are compared with thermally double coupled reactor (TDCR).•Application of membranes and recycle streams enhance the performance significantly.

In this research, effect of water and hydrogen perm-selective membranes via different recycle cases in a thermally double-coupled two-membrane reactor (TDCTMR) has been investigated. Methanol and direct dimethyl ether (DME) synthesis from natural gas as exothermic reactions have been thermally coupled with cyclohexane dehydrogenation as an endothermic reaction. Hydroxy sodalite (H-SOD) and Pd/Ag membranes have been employed for removing water from methanol side and injection of hydrogen to DME side respectively. Three different recycle stream cases have been studied for the performance enhancement of TDCTMR. In the first case, the outlet stream from DME reactor is recycled to itself. Also, in the second case, the outlet stream from methanol side is recycled to DME side and finally, the third case is that the mixture of methanol and DME outlet streams are recycled to DME side. The results of these three cases are compared with thermally double coupled reactor (TDCR). Results show that hydrogen production in cyclohexane side of TDCTMR increases 8.32%, 22.89% and 23.88% for cases 1, 2 and 3 in comparison to TDCR respectively. Also, DME and methanol production enhances 38.38% and 13.3% for case 3 (best case) in comparison to TDCR respectively.