液相法结合冷冻干燥技术制备Li₄SiO₄材料及其高温二氧化碳吸收性能

A Liquid Phase Method Combined with Freeze-Drying Technique to Lithium Silicate Materials and Their Carbon Dioxide Absorption Properties at High Temperatures

摘要: 选用LiOH∙H₂O、LiNO₃、Li₂CO₃为锂源，硅溶胶为硅源，采用液相法结合冷冻干燥技术制备了Li₄SiO₄材料，采用热重分析(TGA)研究了Li₄SiO₄前躯体的失重行为，采用X射线粉末衍射仪(XRD)和扫描电子显微镜(SEM)对Li₄SiO₄材料的结构和形貌进行分析。在热重分析仪(TGA)上考察了制备材料的高温CO₂吸收性能，发现以LiOH∙H₂O为锂源时，合成材料的吸收性能最好。考察了该材料在不同温度、不同CO₂分压下的高温CO₂吸收性能，结果表明，在吸收温度为550℃，CO₂分压为0.25 bar时，样品在5 min时吸收量为24.1 wt%，10 min内即可达到吸收平衡，平衡吸收量为29.9 wt%。经过5次吸收-解吸后，吸收速率、吸收量都没有出现明显下降。

Abstract: A liquid phase method combined with the freeze-drying technique was developed to synthesize Li₄SiO₄ materials using LiOH∙H₂O, LiNO₃, Li₂CO₃ and silica sol as the lithium and silicon sources, respectively. The weight loss behaviors of the prepared Li₄SiO₄ precursors were investigated by the thermal gravimetric analysis (TGA). The structure and morphology of the prepared Li₄SiO₄ materials were characterized by XRD and SEM, respectively. The CO₂ absorption properties of prepared Li₄SiO₄ were investigated by thermal gravimetric analysis (TGA). The results show that the Li₄SiO₄ material prepared using LiOH∙H₂O as the lithium source presents the best CO₂ absorp-tion property among the prepared Li₄SiO₄ materials. The CO₂ absorptions at different temperatures and different CO₂ partial pressures have been performed on the optimized Li₄SiO₄ material. The absorbed amount of CO₂ reaches 24.1 wt.% within 5 min and an equilibrium amount of 29.9 wt.% is achieved within 10 min at 550˚C and a partial pressure of 0.25 bar. Additionally, after five absorption-desorption cycles, the sorbent still maintains its original properties in terms of capture rate and absorption amount.