Thermodynamic analysis and optimization of solar methane dry reforming enhanced by chemical hydrogen separation

Thermodynamically limited reactions in membrane reactors for hydrogen generation require a high hydrogen concentration gradient for separation, which imposes an energy requirement that reduces the process energy efficiency. To decrease the required separation energy, chemical hydrogen separation by CO₂ is proposed by combining solar-driven dry reforming of methane (DRM) in a hydrogen permeable membrane (HPM) reactor with either reverse water gas shift (RWGS) or methanation. This system has the benefit of using solar renewable energy as well as reducing CO₂ emissions. The performances of the proposed membrane reactor configurations for in situ hydrogen consumption are compared to DRM and super-dry reforming of methane (SDRM) in a fixed-bed reactor. The thermodynamic, kinetic, and environmental performances are analyzed and compared from 300 °C to 1000 °C. 2.01 mol CO₂ can be reduced to CO per mole CH₄ consumed at 1000 °C by coupling DRM with RWGS in a membrane reactor, resulting in a CO₂ reduction rate of 1064 kg m⁻² yr⁻¹. Alternatively, the minimum energy consumption per mole CO₂ converted is 0.79 MJ at 860 °C. This study demonstrates the feasibility of DRM enhanced by chemical hydrogen separation in HPM reactors to convert CO₂ into fuels and store solar thermal energy as chemical energy.