CaO-based dual functional materials for ICCU-DRM

Integrated CO₂ capture and utilisation for syngas production using methane as the reducing agent are very promising for solving two greenhouse gases (methane and CO₂). Using methane to reduce CO₂ also has better economic feasibility than using H₂. Early work was reported about ICCU-DRM (dry reforming of methane) using Ni/MgO-Al₂O₃ DFM, prepared by coprecipitation (https://doi.org/10.1021/acscatal.7b03063). During the ICCU experiments, 20% CO₂ in N₂ was used as the CO₂ source, and 2.4% CH₄ in N₂ was used as the reducing agent. The DFM is a mixture of calcined limestone and Ni/MgO-Al₂O₃ catalyst. Very supervising results are reported with almost 100% conversion of CO₂ and methane (as shown in the below figure).

This needs to be further tested as the decomposition of CaCO₃ could not be avoided at 720 °C. Thus a significant amount of CO₂ is expected in ICCU. However, this is not researched in detail about the mechanism behind the excellent ICCU performance. It is noted that a paper published in Science Advance (DOI: 10.1126/sciadv.aav5077) demonstrated that CO₂ utilisation efficiency was about 65% and the conversion of methane was about 86%, when Ni/CaO DFMs were used. The key difference between these two papers is the involvement of MgO and Al₂O₃. This Science Advance paper also indicated that the presence of Ni was essential for ICCU, and using CH₄ as a reducing agent could significantly enhance the kinetics of CaCO₃ decomposition (as indicated below).

DFMs containing Ni, CeO₂ nanoparticles, ZrO₂ and CaCO₃ were reported for ICCU-DRM. ZrO₂ played a key role in stabilising both CaO and particles, maintaining the performance of CO₂ capture and utilisation. The presence of CeO₂ prohibited the formation of coke and also enhanced the activation of CO₂ and CH₄. However, only over 40% conversion of CH₄ and CO₂ was reported. Experimental conditions for this work are below:

“The performance of the bifunctional materials for cyclic CO₂ capture and conversion was compared by performing 25 cycles of CaLDRM process at 720 °C and 1 bar. Each cycle comprises 2 min CO₂ capture step (i.e. CaO carbonation) in 5 vol% CO₂/Ar (30 N mL min⁻¹) followed by 2 min DRM step (accompanied by CaO regeneration) in 8 vol% CH₄/Ar (30 N mL min⁻¹). ”