NaNO 3 ‐Promoted Mesoporous MgO for High‐Capacity CO 2 Capture from Simulated Flue Gas with Isothermal Regeneration

NaNO 3 ‐promoted MgO composite materials have been prepared and their ability to sorb CO 2 at a concentration relevant to CO 2 capture from flue gas is explored. The uptake kinetics and capacities of sorbents of different NaNO 3 /MgO ratios are measured at intermediate temperatures of 230–300 °C. The sorbent with a NaNO 3 /MgO ratio of 0.10 has the highest 12 h sorption capacity among sorbents with different NaNO 3 loadings, and the highest sorption capacity of 11.2 mmolCO2 g −1 is observed at 260 °C. Intriguingly, an induction period is observed in the initial stage of CO 2 sorption. In situ XRD analysis, in situ FTIR spectroscopy, and a comparison of the CO 2 sorption behavior under simulated flue gas conditions in comparison to prior studies employing pure CO 2 indicated that the sorption of CO 2 occurred through nucleation of MgCO 3 crystallites in the material. The data indicate that the concentration of CO 2 within the molten medium of NaNO 3 , which is affected by both the solubility of CO 2 in molten NaNO 3 and the partial pressure of CO 2 in the surrounding atmosphere, has a critical impact on the length of the induction period. A partially desorbed sample after sorption of CO 2 displays much‐improved sorption kinetics in the next cycle and was able to sorb and desorb CO 2 over multiple cycles at isothermal conditions by simply switching the feed gas from CO 2 to inert gas.