Abstract:

The consumption of fossil fuels has led to a series of environmental issues due to CO₂ emissions, drawing increasing attention to carbon capture and storage (CCS) technology. Lithium silicate (Li₄SiO₄) is considered a highly promising sorbents due to its high CO₂ capture capacity, low regeneration temperature, and good thermal stability. However, its widespread application is limited by the high cost of silicon sources and insufficient cycling performance. Low?cost fly ash was used as silicon source to synthesize Li₄SiO₄ via solid?state and impregnation?precipitation methods, followed by modification with K₂CO₃ doping. The materials were characterized by testing methods such as XRF, XRD, and SEM.The results show that the sorbents prepared by the solid?phase method at 700 °C (LS?700) possesses a rich pore structure and a high specific surface area of 1.584 2 m2/g, and exhibits the optimal sorption performance, with the CO? sorption capacity remaining at 0.179 7 g/g after 10 cycles. After K₂CO₃ doping, the CO₂ sorption rate increased to 0.054 5 g/(g·min), which is 1.4 times that of the undoped sample. Mechanistic studies revealed that the formation of a low?temperature eutectic layer between K₂CO₃ and Li₂CO₃ promoted CO₂ diffusion and reduced the reaction activation energy. This study provides an effective strategy for developing low?cost and high?performance Li₄SiO₄?based sorbents, demonstrating significant value for enhancing CO₂ capture efficiency from coal?fired flue gas.

Key words: Carbon capture, Li₄SiO₄, Solid sorbents, Kinetics, Reaction mechanism

摘要：

化石燃料消耗导致的CO₂排放引发了一系列环境问题，CO₂ 捕集与封存技术（CCS）备受关注。硅酸锂（Li₄SiO₄）吸附剂因吸附容量大、再生温度低和热稳定性好而极具潜力，但面临硅源成本高与循环性能不足的挑战。以廉价粉煤灰为硅源，采用固相合成法和浸渍沉淀法制备了Li₄SiO₄，并通过掺杂K₂CO₃对其进行了改性；通过XRF、XRD、SEM等测试方法，对材料进行了表征。结果表明，700 ℃固相法制备的吸附剂（LS?700）具有丰富的孔隙结构和高达1.584 2 m²/g的比表面积,吸附性能最优，10次循环后CO₂吸附量保持在0.179 7 g/g；K₂CO₃掺杂使CO₂吸附速率提高至0.054 5 g/（g?min），是未掺杂吸附剂的1.4倍；K₂CO₃与Li₂CO₃形成的低温共熔层促进了CO₂的扩散并降低了反应活化能。该研究为低成本、高性能Li₄SiO₄吸附剂的开发提供了有效途径，对推进燃煤烟气CO₂的高效捕集具有重要价值。

关键词: 碳捕集, 硅酸锂, 固体吸附剂, 动力学, 反应机理