氯化镁改性硅胶的吸水等温线及脱附性能

WATER VAPOR ADSORPTION ISOTHERM AND DESORPTION PROPERTY OF MAGNESIUM CHLORIDE MODIFIED SILICA

用氯化镁改性硅胶制备复合干燥剂,在相对湿度为20%～90%的条件下研究氯化镁改性硅胶对水蒸气的吸附,采用FHH(Frenkel–Halsey–Hill)模型研究复合干燥剂表面的粗糙程度,测定水在改性硅胶上的程序升温脱附曲线,考察复合干燥剂的再生温度、再生次数及氯化镁改性对硅胶吸湿性能和水的脱附活化能的影响。结果表明:在相同条件下,氯化镁含量为1%时,改性硅胶的吸水量约为未改性硅胶的10倍,改性硅胶吸水符合第Ⅳ型等温线。通过FHH模型分析说明改性后硅胶的大片状固体颗粒被部分破坏,形成更为精细的孔隙分布,硅胶表面更加粗糙和不规则。程序升温脱附研究表明氯化镁改性硅胶的脱附活化能较小,脱附容易进行。脱附再生3次后,改性硅胶仍具有较高的吸水量,复合干燥剂具有较好的再生性能。

A new kind of compound desiccant was prepared by magnesium chloride modified silica gel.A measurement of moisture uptake curves in magnesium chloride modified silica gel was performed by using the thermal gravimetrical method in a relative humidity range from 20% to 90%,the Frenkel–Halsey–Hill（FHH） model is used to study the rough degree of the surface of the modified silica.The temperature program desorption（TPD） curves of water on the modified silica were measured by means of the TPD technique,and then the corresponding activation energies of water desorption were also estimated.The results show that the water vapor adsorption capacity of silica was greatly enhanced after modified by magnesium chloride,which is 10 times higher than unmodified silica.The isotherm of modified silica fits well of type Ⅳ.The FHH model shows that after modification the big structure is ruinated and the little pore forms,the surface is much rougher of modified silica than unmodified silica.The desorption activation energy of water on the modified silica is much lower,so the desorption is easy to operate.After three times regeneration,the water vapor capacity is still high.