Preparation And High-temperature Co₂ Adsorption Performance Of CaO-based Sorbents

Global warming has brought about a series of environmental problems owing to the soaring emission of CO₂.Carbon capture and storage（CCS）turns out to be a viable solution.Based on the hard template method and sol-gel method,the effects of doping Mn and Ti on the microstructure,the electronic states and CO₂ adsorption performance of calcium-based sorbents were respectively explored.Novel Mn-promoted hollow calcium-based microspheres were successfully fabricated via a versatile hard template method using carbon microspheres as templates,achieving the controllable adjustment of Ca/Mn molar ratio,microsphere size,shell thickness and shell number.Smaller microsphere size was beneficial for the improvement of CO₂ capacity but harmful for the adsorption stability.The thin shells could decrease diffusion resistance and shorten the diffusion pathways of CO₂.The CO₂ uptake of microspheres with double shells surpassed the single-shelled counterparts owing to more reactive sites.The Mn-promoted double-shelled hollow calcium-based microspheres effectively handled the collapsing problem led by the continuous volume variations and exhibited excellent adsorption performance,which notably outperformed that of the pure Ca CO₃counterpart.The uniformly distributed Mn considerably enhanced structural stability of sorbents and reduced the crystalline size of Ca CO₃.Furthermore,the doping of Mn promoted the ability of donating electrons of Ca O to CO₂ and was presumably to bring about oxygen vacancies.The sorbent Ca12Mn1-500 exhibited an initial capacity of 0.62 g-CO₂/g-ads and a final capacity of 0.53 g-CO₂/g-ads after 25 adsorption-desorption cycles.A series of Ti-doped calcium-based sorbents were prepared by a sol-gel method.The homogeneous distributed Ca Ti O₃ could effectively inhibit the sintering of sorbents,thus significantly enhancing the adsorption stability.The specific surface areas and mesoporous amounts of the sorbents could be significantly increased by doping Ti.Due to the large specific surface area（39 m²/g）and mesoporous structure,as well as the enhanced ability of Ca O to transfer electrons to CO₂,sorbent Ca2Ti1exhibited excellent CO₂ adsorption performance,of which the conversion could reach up to 97%and basically remain unchanged through 25 cycles.