Characteristics of Alkali Nitrates Molten Salt-Promoted MgO as a Moderate-Temperature CO2 Absorbent

The process of carbon capture and sequestration has been proposed as a method of mitigating the build-up of greenhouse gases in the atmosphere. We report several alkali nitrates molten salts promoted MgO-based CO2 sorbent with superior CO2 capture performance over that of neat MgO. The influence of chemical composition, loading, and melting temperature of alkali nitrates molten salts, and of the calcination and adsorption temperatures on CO2 capture was evaluated systematically. The MgO sample doped with 10 mol% (LiNO3-NaNO3-KNO3,25-62-13 wt. %, m.p.135 C,Opt) and another kind of molten salt composed of NaNO3-KNO3-NaNO2 (7-53-40 wt. %, m.p.142 C, HITEC) was demonstrated to possess the high CO2 uptake (up to 13.52 mmol g-1 and 10.53 mmol g-1 respectively). The microstructural and morphological evolution of samples during CO2 adsorption was studied by XRD, FTIR, and SEM. The loading of alkali nitrates molten salts was believed to prevent the formation of a rigid MgCO3 layer on the surface of MgO particles and provide a continuous delivery of C032- to promote CO2 capture. The melting point of molten salts is also a crucial factor in the improvement of CO2 uptake. (C) 2019 The Authors. Published by Elsevier Ltd.