A solar-assisted two-stage catalytic membrane reactor for CO₂ splitting

As major greenhouse gases, CO₂ and CH₄ are the primary drivers of climate change. Hence, utilizing CO₂ and CH₄ as feedstocks for the synthesis of value-added chemicals offers significant economic and environmental benefits. However, the principal challenges associated with converting these two molecules pertain to their kinetic stability and thermodynamic equilibrium limitation.

Catalytic membrane reactors based on oxygen-permeable perovskite membranes can realize the bi-functions of oxygen separation and heterogeneous catalytic reactions in a single unit, thereby enabling simultaneous conversion of CO₂ and CH₄ and offering superior advantages over conventional fixed-bed reactors.

Nonetheless, there remain issues such as the discrepancy between the catalytic reaction rate and the O₂ separation rate, the low single-pass CO₂ conversion (less than 30%), and the substantial energy input requirement.

To that end, Wanqin Jin and his co-workers from Nanjing Tech University designed a unique two-stage catalytic membrane reactor that employs an asymmetric oxygen-permeable membrane and solar irradiation for CO₂ splitting (2CO₂→2CO+O₂) and CH₄ oxidation to syngas.

The research is published in the journal Green Energy & Environment.

“In our designed catalytic membrane reactor, the oxygen generated from the CO₂ splitting reaction can be extracted through the oxygen-permeable membrane with 100% selectivity, and subsequently employed for solar-assisted methane combustion and reforming,” says Guangru Zhang, co-corresponding author of the study.

“The solar-assisted catalytic membrane reactor achieves a prominent CO₂ conversion of 35.4% and H₂ yield of 18.1 mL min^-1 cm^-2 which is 62- and 1.5-times higher than that of a fixed-bed reactor and a catalytic membrane reactor without solar irradiation, respectively.”

Notably, the design of the two-stage catalytic membrane reactor also provides excellent flexibility for selecting membrane configurations including disk- and hollow fiber-shaped membrane. This design is expected to realize the coupling of diverse chemical reactions or processes on both sides of hollow fiber membrane with different operating temperatures and pressures.

“Our work provides an innovative strategy for reducing CO₂ emissions, with the potential to mitigate the carbon footprint across industrial sectors,” added another senior and corresponding author, Wanqin Jin.