Kinetic and reaction mechanism of CO2 sorption on Li4SiO4:: Study of the particle size effect
Kinetic and reaction mechanism of CO2 sorption on Li4SiO4:: Study of the particle size effect
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DOI：
10.1021/ie061259e
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发表时间：
2007-04-11
影响因子：
4.2
通讯作者：
Pfeiffer, Heriberto
中科院分区：
文献类型：
--
作者：
Venegas, Miriam J.;Fregoso-Israel, Esteban;Pfeiffer, Heriberto
采用固相反应法、沉淀法和溶胶-凝胶法(微波炉)合成了正硅酸锂(Li4SiO4)。前两种方法取得了较好的效果。在第三种情况下，由于微波产生了锂升华，因此无法获得纯的Li4SiO4。用X射线衍射仪、扫描电子显微镜、氮气吸附和CO2流量下的热重分析对样品进行了表征。不同的合成方法得到了不同的颗粒尺寸，CO2吸附分析给出了不同的结果。颗粒大小改变了Li4SiO4在CO2吸附/脱附循环中的稳定性，这是由于锂升华为Li2O所致。相反，等温研究允许测量化学吸附和扩散过程的动力学参数，作为颗粒大小的函数。正如可以预期的那样，对于小颗粒获得的活化能小于对于大颗粒获得的活化能。这些结果从反应性、化学吸附过程和几何结构、扩散过程的角度进行了解释。
Lithium orthosilicate (Li4SiO4) was synthesized by three different techniques: the solid-state reaction, precipitation, and sol-gel (using a microwave oven) methods. The better results were obtained by the two first methods. In the third case, pure Li4SiO4 could not be obtained, because the microwaves produced the lithium sublimation. The samples were characterized by X-ray diffraction, scanning electron microscopy, N-2 adsorption, and thermogravimetric analysis under a flux of CO2. Different particles sizes were obtained as a function of the method of synthesis, and the CO2 sorption analyses gave different results. The particle size modified the stability of the Li4SiO4 during the CO2 sorption/desorption cycles, due to lithium sublimation, as Li2O. Conversely, the isothermal study allowed measuring the kinetic parameters for the chemisorption and diffusion processes, as a function of the particle size. As could be expected, the activation energies obtained, for the small particles, were smaller than those obtained for the large particles. These results were explained in terms of reactivity, for the chemisorption process, and in terms of geometry, for the diffusion process.