Kinetic and Thermodynamic Characterization of Enhanced Carbon Dioxide Absorption Process with Lithium Oxide-Containing Ternary Molten Carbonate.

Efficient and high-flux capture of CO is the prerequisite of its utilization. Static absorption of CO with solid LiO and molten salts (LiO-free and LiO-containing Li-Na-K carbonates) was investigated using a reactor with in situ pressure monitoring. The absorption capacity of dissolved LiO was 0.835 mol/mol at 723 K, larger than that of solid LiO. For the solid LiO absorbents, formation of solid LiCO on the surface can retard the further reactions between LiO and CO, whereas the dissociation/dissolution effect of molten carbonate on LiO improved the mass-specific absorption capacity of liquid LiO. In LiO-containing Li-Na-K molten carbonate, CO was mostly absorbed by alkaline oxide ions (O). The chemical interactions between CO and CO contributed to CO uptake via formation of multiple carbonate ions. The mass transfer of these absorbing ions was found as the dominating factor governing the rate of static absorption. Higher temperatures reduced the thermodynamic tendency of CO absorption, but a lower viscosity at elevated temperature was conducive to absorption kinetics. Compared with the commonly used CaO absorbent, LiO was much more dissolvable in molten carbonate. The LiO-containing molten carbonate is potentially a promising medium for industrial carbon capture and electrochemical transformation process.