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

Efficient and high-flux capture of CO2 is the prerequisite of its utilization. Static absorption of CO2 with solid Li2 O and molten salts (Li2 O-free and Li2 O-containing Li-Na-K carbonates) was investigated using a reactor with in situ pressure monitoring. The absorption capacity of dissolved Li2 O was 0.835 molCO2 /molLi2 O at 723 K, larger than that of solid Li2 O. For the solid Li2 O absorbents, formation of solid Li2 CO3 on the surface can retard the further reactions between Li2 O and CO2 , whereas the dissociation/dissolution effect of molten carbonate on Li2 O improved the mass-specific absorption capacity of liquid Li2 O. In Li2 O-containing Li-Na-K molten carbonate, CO2 was mostly absorbed by alkaline oxide ions (O2- ). The chemical interactions between CO2 and CO3 2- contributed to CO2 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 CO2 absorption, but a lower viscosity at elevated temperature was conducive to absorption kinetics. Compared with the commonly used CaO absorbent, Li2 O was much more dissolvable in molten carbonate. The Li2 O-containing molten carbonate is potentially a promising medium for industrial carbon capture and electrochemical transformation process.