Magnesite-derived MgO promoted with molten salts and limestone as highly-efficient CO2 sorbent

This study evaluated the CO2 capture performance of MgO obtained from mineral magnesite and doped with limestone and molten Li, Na and K nitrates under consecutive sorption/desorption cycles via thermogravimetric analysis. Increasing the molten promoter loading resulted in a higher CO2 sorption rate, while elevated CaCO3 amounts impeded CO2 diffusion. When exposed to a 30 % CO2 flow at 300 degrees C for 30 min, the sorbent with alkali salts and CaCO3 to MgO molar ratios of 0.20 and 0.05 respectively attained a capture of 7.2 mol CO2/kg of sorbent and a negligible activity loss (similar to 6%) after 50 cycles. This performance was promising, considering the mineral nature of precursors. In-situ X-ray diffraction revealed the growth of the MgO crystal after each desorption, proving the gradual MgO sintering. However, the morphological transformations occurring during cyclic operation and especially if high conversions of MgO are reached, trigger an alkali salt redistribution that grants high stability.

Automated summary

This study investigated the CO2 capture performance of MgO derived from mineral magnesite doped with limestone and molten Li, Na, and K nitrates, showing that increasing the molten promoter loading can enhance CO2 sorption rate, while higher CaCO3 content impedes CO2 diffusion. Despite morphological transformations during cyclic operation, redistribution of alkali salts contributes to the stability and promising performance of the sorbent.