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

Abstract

CO 2 sorption on the NaNO 3 incorporated MgO sorbent at 573-673 K has been resulted in the formation of MgCO 3 , referred from the results of in-situ X-ray powder diffraction combined with FT-IR spectrum. There was no interaction between CO 2 and NaNO 3 incorporated MgO sorbent before the melting of NaNO 3 . The fraction of MgCO 3 was increased significantly while the NaNO 3 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% NaNO 3 and 8 wt% KNO 3 impregnated on MgO lower the temperature for CO 2 sorption to ca. 498 K. Therefore, it was suggested that the dissolution of CO 2 in liquid metal nitrate was a critical step for the CO 2 capture as Mg carbonate salts.

CO2 Uptake and Cyclic Stability of MgO-Based CO2 Sorbents Promoted with Alkali Metal Nitrates and Their Eutectic Mixtures

“…Indeed, the onset temperature for the carbonation of MgO could be reduced further by its promotion with eutectic mixtures of alkali metal nitrates. 51 Figure 2a shows that, by lowering the melting point of the promoter through the use of a (Na,K)NO 3 eutectic mixture (60% NaNO 3 , 40% KNO 3 ; MP = 230 °C), the onset temperature of carbonation is reduced to 230 °C. Using a ternary eutectic mixture (Li,Na,K)NO 3 , MP = 120 °C), the onset temperature of carbonation is reduced further to 160 °C.…”