Enhancing CO2 chemisorption on lithium cuprate (Li2CuO2) at moderate temperatures and different pressures by alkaline nitrate addition

Abstract

Lithium, sodium and potassium nitrate-containing Li₂CuO₂ samples were prepared to analyze the CO₂ capture process at moderate temperatures, using different pressure conditions. Initially, in a CO₂ saturated atmosphere, all these samples showed high CO₂ capture efficiencies between 150 and 350 °C, in comparison to the pristine Li₂CuO₂ (T ≥ 500 °C). These results evidenced that Li-, Na- and K-nitrate addition on Li₂CuO₂ importantly enhances the whole CO₂ capture. These results were corroborated kinetically. Moreover, the effects and reaction mechanism of alkaline nitrate addition were determined by X-ray diffraction, infrared spectroscopy and differential scanning calorimetric analyses. Nitrate anions melt and work as donor/acceptor oxygen anion intermediates during the Li₂CuO₂ carbonation process. Moreover, the carbonation may be completed (Li₂CO₃ and CuO production) through Li₃Cu₂O₄ formation. When the CO₂ capture process was evaluated using low partial pressures, the results presented similar efficiencies to those obtained using a saturated CO₂ condition, showing differences only during the decarbonation process (T > 700 °C), as the CO₂ chemisorption–desorption equilibrium was shifted. Finally, pristine Li₂CuO₂ and alkaline nitrate-containing Li₂CuO₂ samples were evaluated at high pressures. The pristine Li₂CuO₂ sample did not show any CO₂ capture improvement, while alkaline nitrate-containing Li₂CuO₂ samples did improve. This was attributed to the alkaline nitrate melting process and the pressure equilibrium conditions.