Photothermal Tandem Catalysis of CH4 Reforming and Fischer-Tropsch Synthesis to Produce Syngas and C2+ Hydrocarbons

Photothermal catalysis is a promising approach for converting renewable solar energy to storable chemical energy. However, a critical challenge in photothermal catalysis lies in the temperature gradients formed under irradiation within the catalyst bed. In the present study, this temperature gradient is utilized to promote tandem reactions of the highly endothermic CH₄ reforming at the high-temperature zone to produce syngas and the exothermic Fischer-Tropsch synthesis (FTS) at the low-temperature zone to yield C₂₊ hydrocarbons. This study demonstrates that C₂₊ hydrocarbons such as ethane and ethylene are formed using a single photoreactor with a temperature gradient from CO₂ and CH₄ as carbon sources via the tandem reactions over SiO₂-encapsulated Co–Ni alloy catalysts. Almost no C₂₊ formation under uniform temperature conditions in an electric furnace highlights the essential role of the temperature gradient in C₂₊ formation. Moreover, this study reveals that the fabrication of the porous SiO₂ shell and the addition of steam into the feed gas have a crucial impact on the C₂₊ formation rate. This work may open new avenues for tandem reaction systems from two greenhouse gases of CO₂ and CH₄ into value-added C₂₊ hydrocarbons.