A gap-designed photo-reactor for high-performance photothermal methane reforming†

Photothermal catalysis has garnered significant attention as a potential solution to address energy scarcity. In photothermal catalysis, light irradiation directly heats the catalyst bed, inducing a localized temperature gradient. However, in methane reforming reactions such as dry reforming, the undesired reverse reaction typically proceeds in the lower temperature zone of the catalyst bed, which reduces the overall efficiency. To address this issue, we developed a novel flow-type photo-reactor composed of a quartz tube and a quartz filler welded within the tube. The narrow catalyst-filled gap was used for catalytic reaction that minimizes the temperature gradient under light irradiation. The developed reactor, termed the gap reactor, demonstrated excellent catalytic performance in photothermal dry reforming of methane (PT-DRM), achieving ∼70–80% conversion of CH₄ and CO₂ over 100 hours using a SiO₂-encapsulated Co–Ni alloy catalyst previously developed by our group. Compared to the conventional quartz tube reactor with the same cross-sectional area for light absorption, the gap reactor significantly enhanced both conversion and stability. Furthermore, integrating the gap reactor with steam addition to the reaction feed successfully suppressed coke formation to only 0.6 wt% after approximately 50 hours of reaction. This study highlights the benefits of the gap reactor design in high-temperature catalytic applications up to 1000 °C.