新型Li_4SiO_4高温吸收CO_2的动力学研究

Kinetics of novel Li_4SiO_4 absorbing CO_2 at high temperature

高温固体CO2吸收剂硅酸锂材料以其较高的吸收容量、优良的循环吸收稳定性成为研究热点。文中以廉价的、具有丰富孔结构的硅藻土和碳酸锂为原料,采用高温固相法于600℃下合成了可在高温直接吸收CO2的硅酸锂材料。XRD结果分析表明所制备的材料由Li4SiO4和少量的LiAlSi2O6相组成,用同步热重分析仪(TG-DSC)研究了在等温条件下硅酸锂材料吸收CO2的性能。用双指数模型拟合了硅酸锂材料吸收CO2的过程。结果表明:吸收CO2的温度不同,硅酸锂材料吸收CO2反应的控制步也不相同。表面反应速率常数与扩散速率常数的相对大小在很大程度上影响了硅酸锂材料吸收CO2的性能。

With the cheap porous diatomite and lithium carbonate as raw materials, lithium silicate material was prepared by the solid-state reaction method at 600 ℃, and used for high temperature CO2 capture. The X-ray diffraction result indicated that LinSiO4 phase and a small amount of LiAlSi206 phase were observed in the resultant materials, and the CO2 absorption properties at the isothermal conditions were studied by the simultaneous thermal thermogravimetric analyzer （TG-DSC）. The isothermal study data were fitted according to a double exponential model. The results show that different absorption temperature results in different control steps in the process of Li4SiO4 absorbing CO2. The ratio of the surface reaction rate constant to diffusion rate constant has an important influence on the CO2 absorption properties.