La1.5Sr0.5NiO4±δ–Molten Carbonate Dual-Phase Membrane Reactor for O₂/CO₂ Cotransport and Oxidative Coupling of Methane to Synthesize C₂ Products

Direct methane conversion into ethylene and ethane, named the oxidative coupling of methane (OCM), has attracted much attention in chemical industrial processes. To alleviate deep oxidation and decrease the O2 separation and CO2 capture costs, here we report a coupling of O2/CO2 cotransport from simulated flue gas with an in situ OCM reaction through a La1.5Sr0.5NiO4±δ–molten carbonate dual-phase membrane reactor over the La–Sr/CaO catalyst. The results show that the fluxes of O2 and CO2 increase with the presence of methane in sweep gas. In addition, the transport direction of O2– changes due to the different oxygen partial pressures on the membrane sweep side surface. A higher OCM performance was obtained by the membrane reactor compared with the traditional fixed-bed reactor. At 850 °C, the CH4 conversion, C2 selectivity, and yield of the membrane reactor are 28.0%, 43.8%, and 12.3%, respectively, while those of the fixed-bed reactor are 25.3%, 27.2%, and 6.9%, respectively. A stability test of the OCM performance in the membrane reactor shows no degradation within 100 h at 850 °C. These results suggest that the membrane reactor is promising for coupling O2/CO2 cotransport with the in situ OCM process.