Preparation And CO₂ Adsorption Performance Of Magnesium-doped Calcium-based Sorbents

The massive combustion of fossil fuels by humans has led to excessive emissions of CO₂ in the air,which has caused various environmental problems and seriously threatened the development of human society.Calcium looping technology were considered as a promising CO₂ capture method based on its efficient adsorption performance and economic feasibility.In this paper,the effects of organic calcium source precursors and incorporation of MgO on the morphology,structure and CO₂adsorption performance of CaO powder and pellets sorbent were investigated.The calcium source precursor of Ca-MOF was prepared by the ultrasound-assisted method and compared with commercial Ca CO₃.Two calcium source precursors were calcined under the same conditions to prepare CaO sorbents,and the influence of calcium source precursors on the CO₂adsorption performance of CaO sorbents was explored.The results showed that CaO sorbent derived from Ca-MOF has a higher CO₂cyclic adsorption capacity.A series of magnesium-doped calcium-based powder were prepared by the impregnation method,and the Ca-MOF were used as the calcium source precursor,the effect of the addition of inert component MgO on the morphology,structure and CO₂ cyclic adsorption performance of the CaO sorbent was investigated.The inert component of MgO was homogeneously dispersed in sorbent to form an effective physical barrier and changed the surface morphology and pore structure of sorbent,which were effectively enhanced the anti-sintering ability and long-term adsorption stability of the sorbent.The long-period CO₂ adsorption stability of the sorbent were gradually increased with the increase of MgO content in the sorbent.Ca5Mg3 sorbent exhibited excellent CO₂ adsorption performance and long-term stability,CO₂ adsorption capacity of Ca5Mg3 sorbent is 10.67 mmol·g^-1after 30cycles,which is significantly higher than the CO₂adsorption capacity(7.39 mmol·g^-1)of the CaO sorbent after 30 cycles.CaO sorbent pellets were one-step molding prepared by gel-casting method,the influence of the presence of sodium ions on the morphology,structure and CO₂adsorption performance of sorbent pellets were investigated.The presence of sodium ions led to the sintering of the sorbent,which is adverse to sorbent adsorb CO₂.Magnesium-doped calcium-based sorbent pellets were prepared by gel casting-impregnation method,the effect of incorporation of MgO on the crystal structure,surface morphology,CO₂ cyclic adsorption performance and adsorption rate were investigated.The inert component MgO was uniformly dispersed in the calcium-based sorbent pellets,magnesium-doped calcium-based sorbent pellets showed a larger specific surface area,smaller CaO grain size and loose surface morphology,therefore,it exhibited faster CO₂ adsorption rate,higher CO₂ adsorption capacity and long-term stability.Ca2Mg1 sorbent pellets exhibited the favorable CO₂ adsorption performance(9.49 mmol·g^-1),higher conversion rate of CaO（74.83%）and faster average adsorption rate(0.32 mmol·g^-1·min^-1)after 30 cycles.