Unveiling the dynamic CO₂ capture performance of MgO promoted with molten salts and CaCO₃ via fixed bed reactor experiments

Carbonate looping using MgO-based materials has recently ignited scientific interest for CO₂ capture at intermediate temperatures (275-375 °C), with the main limitation being the slow carbonation kinetics of MgO. Molten alkali nitrates and metal carbonates have been identified as promoters that provide an alternative reaction mechanism for an enhanced carbonation rate. However, the evaluation of the ability of these materials to effectively remove CO₂ from a gas feed under realistic reactor configurations is still required. This study investigated the CO₂ capture performance of magnesite-derived MgO promoted with limestone and molten Li, Na and K nitrates under carbonate looping conditions in a fixed bed reactor. The CO₂ capture efficiency was enhanced in the presence of H₂O, by increasing the gas-solid contact time and by decreasing the carbonation temperature. The evaluation demonstrated that ∼75% CO₂ stripping of a gas feed with 30% CO₂ concentration at 275 °C and a space velocity of 300 h⁻¹ is possible, a performance that highlights and expands the potential and possible applications of MgO-based materials.