CaCl_2/LiCl改性中孔硅胶的吸附/脱附性能

Adsorption/Desorption Properties of Mesoporous Silca Gel Modified with CaCl_2/LiCl

使用不同的金属盐溶液对中孔硅胶进行改性,并采用间歇式吸附方法研究了水蒸气在硅胶上的吸附动力学实验,利用程序升温脱附技术测定了水在改性硅胶上的程序升温脱附(TPD)曲线并估算了水的脱附活化能,讨论了表面改性对硅胶吸湿性能以及水的脱附活化能的影响.实验结果表明:与C型中孔硅胶相比,经CaC l2或LiC l改性的中孔硅胶,孔容变小而平均孔径变大,在相对湿度(RH)小于80%的范围内,其吸湿性能明显增加,水的脱附活化能也增大;由于Ca2+的极化势大于Li+的极化势,水分子在经CaC l2改性的硅胶上的脱附活化能要大于其在经LiC l改性硅胶上的脱附活化能.

In this work, mesoporous silica gel was separately modified with CaCl2 or LiCl solution, and the kinetic experiments of water vapor adsorption on the mesoporous silica gels were carried out by means of batch adsorption. The temperature program desorption （TPD） curves of water on the modified mesoporous silica gels are measured by means of the TPD technique, and then the corresponding activation energies of water desorption are also estimated. The effects of surface modification on the hygroscopic ability of the silica gels and the desorption activation energy of water on the modified silica gels were finally discussed. Experimental results show that, in comparison with the unmodified mesoporous silica gel, the average pore diameter of the silica gel modified with CaCl2 or LiCl becomes larger, and the pore volume of the modified silica gel becomes smaller. Its hygroscopic ability is improved, and the desorption activation energy of water on the modified mesoporous silica gels at a relative humidity less than 80% increases. Moreover, the desorption activation energy of water on the mesoporous silica gel modified with CaCl2 is much higher than that on the silica gel modified by LiCl, due to the higher polarizability of Ca^2＋.