CO₂ capture from H₂O and O₂ containing flue gas integrating with dry reforming methane using Ni-doping CaO dual functional materials

Reducing carbon emissions remains a formidable challenge under present energy demands and structures. Integrated CO₂ capture and utilisation (ICCU) provides a promising pathway for directly capturing and simultaneously utilising CO₂ from the diluted exhaust gas. Dry reforming of methane (DRM) can be integrated into the step of catalytic conversion of the captured CO₂ with the advantages of utilising two greenhouse gases to yield valuable syngas (CO + H₂). The process has great challenges of materials development for efficient performance, in particular under realistic conditions such as the presence of O₂ and H₂O in the flue gas. This work investigated the ICCU-DRM using simulated flue gases (10 % CO₂ + 6.7 % O₂ + 6.0 % H₂O) in the presence of Ni-CaO dual functional materials, aiming to optimise Ni loading and metal support interaction. It is found that Ni would significantly sinter and further affect the morphologies of CaO adsorbents, resulting in poorer CO₂ capture performances. More notably, the Ni was firstly oxidised during CO₂ capture and subsequently went through a pre-reduction period in the DRM step. Increased Ni loading decreased the difficulty of activation; however, it derived in more severe carbon deposition. To avert the direct contact of carbon deposition and flue gas, extra carbon steam gasification was introduced, and higher Ni loading contributed to selectively yielding syngas as a by-product. The Ni_10- CaO DFM optimally performed <150s pre-reduction delay, ∼85 % CO₂ conversion and ∼2 H₂:CO ratio in the DRM step and ∼75 % CO selectivity in the CSG step at 650 °C. The interaction between Ni and CaO poorly contributes to the performance due to the poor reducibility and accessibility, and the Ni particle size effects only play as spectators in this integrated process.