CO2 capture and release of Na0.7MnO2.05 under water vapor at 25–150 °C

Abstract

Sodium manganates with a layered structure, Na0.7MnO2.05, have been applied to a novel material for CCUS (CO2 capture, utilization, and storage), capable of capturing CO2 at 25 °C in the presence of water vapor and releasing CO2 at 150 °C. The temperatures of capturing and releasing CO2 of Na0.7MnO2.05 were remarkably lower than those of other traditional metal oxides. The CO2 absorption and desorption properties of Na0.7MnO2.05 were investigated by various methods, such as thermogravimetry, Fourier transform infrared spectroscopy, X-ray diffractometry, and gas chromatography. These investigations confirmed that Na0.7MnO2.05 absorbed CO2 at 25 °C in the presence of water vapor to produce NaHCO3 and a birnessite and the CO2 absorption was promoted by increasing relative humidity and CO2 concentration. The CO2 absorption at 25 °C of Na0.7MnO2.05 was promoted by the formation of a strong basic solution on Na0.7MnO2.05, caused by the elution of Na ions from the interlayer of Na0.7MnO2.05 into water, adsorbed on the Na0.7MnO2.05 surface. Furthermore, Na0.7MnO2.05 was regenerated by heating the CO2-absorbed Na0.7MnO2.05 at temperatures as low as 150 °C. The low-temperature regeneration indicates that Na0.7MnO2.05 can be a low-energy consumption material for capturing and releasing CO2 at low temperatures.