Structure Transformation of Na-Mg Based Salts for CO2 Capture and Storage at High Temperature Probed with Variable Temperature X-ray Powder Diffraction

CO2 sorption on the NaNO3 incorporated MgO sorbent at 573-673 K has been resulted in the formation of MgCO3, referred from the results of in-situ X-ray powder diffraction combined with FT-IR spectrum. There was no interaction between CO2 and NaNO3 incorporated MgO sorbent before the melting of NaNO3. The fraction of MgCO3 was increased significantly while the NaNO3 phase in the MgO sorbent was melted at around 580 K. Further it was demonstrated that the use of eutectic mixture having a low melting point, 496 K, 12 wt% NaNO3 and 8 wt% KNO3 impregnated on MgO lower the temperature for CO2 sorption to ca. 498 K. Therefore, it was suggested that the dissolution of CO2 in liquid metal nitrate was a critical step for the CO2 capture as Mg carbonate salts.