NaNO3 Promoted Mesoporous MgO for High Capacity CO2 Capture from Simulated Flue Gas with Isothermal Regeneration.

NaNO3-promoted MgO composite materials have been prepared and their ability to sorb CO2 at a concentration relevant to CO2 capture from flue gas is explored. The uptake kinetics and capacities of sorbents of different NaNO3/MgO ratios are measured at intermediate temperatures of 230-300 degrees C. The sorbent with a NaNO3/MgO ratio of 0.10 has the highest 12 h sorption capacity among sorbents with different NaNO3 loadings, and the highest sorption capacity of 11.2 mmolCO2 g(-1) is observed at 260 degrees C. Intriguingly, an induction period is observed in the initial stage of CO2 sorption. In situ XRD analysis, in situ FTIR spectroscopy, and a comparison of the CO2 sorption behavior under simulated flue gas conditions in comparison to prior studies employing pure CO2 indicated that the sorption of CO2 occurred through nucleation of MgCO3 crystallites in the material. The data indicate that the concentration of CO2 within the molten medium of NaNO3, which is affected by both the solubility of CO2 in molten NaNO3 and the partial pressure of CO2 in the surrounding atmosphere, has a critical impact on the length of the induction period. A partially desorbed sample after sorption of CO2 displays much-improved sorption kinetics in the next cycle and was able to sorb and desorb CO2 over multiple cycles at isothermal conditions by simply switching the feed gas from CO2 to inert gas.