Integrating capture and methanation of CO₂ using physical mixtures of Na-Al₂O₃ and mono-/ bimetallic (Ru)Ni/Pr-CeO₂

The integrated capture and methanation of CO₂ is hereby realized via the use of physical mixtures of a 12 % Na₂O/Al₂O₃ adsorbent and either a monometallic (10 % Ni/Pr-CeO₂) or a bimetallic (1 % Ru, 10 % Ni/Pr–CeO₂) catalyst. The effect of the weight ratio between the catalyst and the adsorbent components is studied and it is found to exert a great influence in the reaction kinetics and the CH₄ production capacity, with the 1:3 catalyst: adsorbent weight ratio (2.5 wt% Ni for both physically mixed materials and 0.25 wt% Ru for the bimetallic material) providing the highest CH₄ yield. It is further shown that the materials offer high activity, stability and CH₄ selectivity at just 300 °C, even under the co–presence of O₂ and H₂O during CO₂ adsorption, a fact attributable to the preservation of the Ni-CeO₂ contact, which is known to afford a high reducibility to the catalytically active Ni phase. The presence of Ru can further enhance the material reducibility and activity under low operation temperatures and catalyst: adsorbent weight ratios, while also mitigating the negative effect of the O₂ and H₂O presence in the adsorption feed. A CH₄ yield of 0.24 mmol/g after 10 consecutive cycles of CO₂ adsorption (under O₂ and H₂O containing gas) and methanation is achieved for the monometallic Ni-based physically mixed material, compared to 0.29 mmol/g in the case of the Ru–Ni bimetallic physically mixed material.