Enhanced CO2 capture and stability of MgO modified with alkali metal nitrates and carbonates at moderate temperature

BACKGROUND

Magnesium oxide (MgO) is favored for solid-state carbon dioxide (CO2) capture due to its high theoretical adsorption capacity, abundant reserves, low cost, and environmental friendliness. However, its practical application in industry is hindered by low CO2 adsorption capacity under moderate operating conditions. In this work, MgO was modified by a deposition method using LiNO3, NaNO3, KNO3, Na2CO3 and K2CO3 as additives.

RESULTS

The study determines optimal ratios within the [(Li, Na, K)x − (Na, K)]y/MgO system, specifically identifying x = 0.5 and y = 0.15 as most effective. At 275 °C under pure CO2 conditions, the adsorption capacity peaks at 0.631 g CO₂ g⁻¹ adsorbent. Effective regeneration of the adsorbent occurs at 400 °C under 100% N2 for 15 min. Under Integrated Gasification Combined Cycle (IGCC) conditions, the adsorption capacity stabilizes at 0.462 g g⁻¹ after 20 cycles, representing a 25% decrease from initial capacity.

CONCLUSION

Experimental findings demonstrate that the inclusion of alkali metal salts in MgO precursors enhances the adsorbent's microstructure, thereby improving its CO2 capture efficiency and bolstering cycling stability. This research enhances our understanding of the factors influencing CO2 adsorption and cyclic stability in alkali metal salt-promoted MgO, providing valuable insights for further refinement in the formulation and synthesis protocols of MgO-based CO2 adsorbents. © 2024 Society of Chemical Industry (SCI).