变色硅胶与ZSM-5沸石分子筛的吸附脱附特性

针对吸附材料在太阳能吸附空调系统中的应用, 对变色硅胶和ZSM-5沸石对水蒸气的吸附脱附特性进行了实验研究。结果表明, 在一定温度下, 两种吸附材料对水蒸气的吸附速率随相对湿度增大而增加, 但增加幅度逐渐减小。环境温度对材料的吸附脱附性能有重要影响, 低温下易吸附, 高温时易脱附。温度升高, 材料的吸附脱附速率增加, 但平衡吸附量降低, 平衡脱附百分比升高。比较两种吸附材料的吸附特性发现, ZSM-5沸石具有较快的吸附速率, 但是其平衡吸附量低于变色硅胶。与变色硅胶的渐近线型吸附等温线不同, ZSM-5沸石的吸附等温线呈S型。比较两种材料的脱附特性发现, 在温度低于100℃时, ZSM-5沸石的脱附百分比大于变色硅胶。此外ZSM-5沸石能够在高温下进行脱附, 而变色硅胶在高温环境下会失去结晶水而变质, 因此脱附温度必须控制在120℃以下。

Adsorption and desorption characteristics of allochroic silica gel and ZSM-5 zeolite to water

For application in solar cooling system, the adsorption and desorption characteristics of the allochroic silica gel and ZSM-5 zeolite to water vapor have been investigated experimentally. The result has revealed that the adsorption rate increases with the humidity of the air at a given temperature, but the rate increment gets small gradually as the humidity increases. Ambient temperature impacts the adsorption rate seriously. The material tends to adsorb easily at low temperature and to desorb easily in high temperature. As temperature increases, the equilibrium adsorption concentration of material declines though the adsorption rate increases. In comparison, the adsorption rate of ZSM-5 zeolite is higher but its equilibrium adsorption concentration is lower in contrast to allochroic silica gel. The adsorption isotherm of silica gel is exponential and that of ZSM-5 zeolite shows an S-shape. As to the desorption characteristic, the result showed that ZSM-5 zeolite had desorbed faster than silica gel when temperature is lower than 100℃. In addition, ZSM-5 zeolite can desorb perfectly at a higher temperature while silica gel must desorb at the temperature less than 120℃, because a high temperature will cause silica gel lose its crystal water insides and fail to desorb.