Mn-promoted CaO-based adsorbents with enhanced CO2 uptake performance

The adsorption of CO2 over CaO-based adsorbents has been an effective way to capture CO2 at high temperature, but the adsorption capacity was hampered and the cycle durability was poor. To address the said problems, this paper reported the effect of Mn doping on the structure, morphology and CO2 adsorption performances of CaObased adsorbents synthesized by a sol-gel method. The characterization results showed that the addition of Mn was helpful to form abundant micropores and mesopores in the doped CaO-based adsorbent, and Mn can effectively prevent the sintering and agglomeration of CaO particles. Moreover, electron transfer occurred on the modified CaO-based absorbents. These findings suggested that Mn species induced both structural and electronic promotion effect, resulting in smaller particle, higher dispersion and specific surface area of CaO-based adsorbents and formation of some electron-rich oxygen and Ca species, ultimately boosting CO2 adsorption performance. Especially, with the molar ratio of Ca/Mn being 20, the adsorbent Ca/Mn-20 presented the best CO2 uptake and excellent cycle stability (up to 10 cycles). In addition, it can be concluded that the adsorption process of CO2 was more obedient to the pseudo-second-order kinetic model, indicating the adsorption process was dominated by chemical adsorption.