CO2 chemisorption enhancement produced by K2CO3- and Na2CO3-addition on Li2CuO2

Abstract

This work presents a proposal for enhancing CO2 capture over lithium cuprate (Li2CuO2) by alkaline carbonates addition. Lithium cuprate was synthesized via solid-state reaction. Subsequently, portions of Li2CuO2 were mechanically mixed with 10wt% of potassium carbonate (K2CO3), sodium carbonate (Na2CO3) or equal amounts of both carbonates (5–5wt%). All samples were characterized by several techniques and then CO2 chemisorption process was evaluated on different dynamic and isothermal conditions. The presence of K and/or Na carbonates preserves the primary properties of pristine Li2CuO2, such as crystalline phase (DRX) and microstructure (SEM), also allowing to increase textural properties (N2 physisorption) and modifying CO2 desorption abilities (TPD), in comparison with pure material. In general, carbonates addition induces some changes during CO2 chemisorption, depending on the type of carbonate used. On the isothermal tests, it was observed that between 400 and 600°C the sample containing both carbonates presented the best capture performance, capturing between 25.7 and 31.8wt% of CO2 (63.9–79.1% of efficiency). On the other hand, at 700°C, Na-Li2CuO2 sample presented the best capture ability, capturing 30.6wt% of CO2 (76.1% of efficiency). Meanwhile at 650°C, K-Li2CuO2 presented the highest sorption capacity with 40.4wt% of CO2 captured, which represents ∼100% of efficiency. The above results showed that in the same thermal conditions, samples modified with alkaline carbonates improved the CO2 capture process. This enhancement was attributed to the formation of eutectic phases (observed in DSC analysis) between sodium and potassium carbonates added mechanically and lithium carbonate (Li2CO3) formed as result of CO2 chemisorption process. Finally, it was observed that carbonate addition is a feasible way to increase CO2 capture in Li2CuO2 material by means of eutectic phase formation.