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

Abstract

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.