Prospects of MgO-based sorbents for CO2 capture applications at high temperatures

MgO-based materials possess favorable thermodynamic properties that enable them to be used as CO2 sorbents in the temperature range of 300–550 °C — at least theoretically. MgO-based sorbents have seen a boost in activity since the discovery of molten alkali metal salt promoters, and yet, they practically remove CO2 from a gas stream efficiently only at very high pressures (p > 10 bar), rendering them suitable for precombustion, but not for postcombustion CO2 capture schemes. Most of the current performance assessments rely on measurements of the transition between MgO and MgCO3 (or Mg-double carbonates) rather than the ability of the sorbents to actually remove CO2 from a gas stream, which may be misleading regarding their practical use and application. Further, reliable thermodynamic data for sorbents involving Mg-double carbonates is missing, although these materials have large potential for industrial CO2 capture applications.