The role of reverse Boudouard reaction during integrated CO2 capture and utilisation via dry reforming of methane

Abstract

Integrated carbon capture and utilisation (ICCU) is an emerging technology for simultaneous CO2 adsorption and conversion into value-added products. This provides a more sustainable approach compared to carbon capture and storage. Dual-functional materials (DFMs) that couple CO2 sorbents (e.g. CaO) and catalysts (e.g. Ni) enable direct utilisation of sorbed CO2 for reactions like dry reforming of methane (DRM). However, the potential interactions between sorbent and catalyst components within DFMs may induce distinct mechanisms compared to individual materials. Elucidating these synergies and interfacial phenomena is vital for guiding the rational design of DFMs. This article investigates the respective roles of Ni/SiO2 catalyst and sol–gel synthesised CaO sorbent in integrated CO2 capture and utilisation via dry reforming of methane (ICCU-DRM) using a decoupling approach. Through decoupled reactor experiments, it is found that Ni/SiO2 activates CO2 to react with carbon deposits from CH4 decomposition, achieving maximal CO and H2 yields of 43.41 mmol g−1 and 46.78 mmol g−1 as well as 87.2 % CO2 conversion at 650 °C. Characterisation shows that coke would encapsulate Ni nanoparticles and be active for CO2 conversion via Boudouard reaction, indicating sufficient catalyst-sorbent contact is necessary for CO2 spillover. In-situ DRIFTS reveals that no obvious CH4-CaCO3 reaction occurs, CO2 chemisorption on Ni/SiO2 enables the reverse Boudouard reaction, which is further verified by DFT calculations. The findings elucidate the dependent and synergistic roles of Ni/SiO2 and CaO/CaCO3 in ICCU-DRM, and highlight the importance of catalyst-adsorbent interactions in optimising dual-functional materials.