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

doi:10.16085/j.issn.1000-6613.2015.06.036

Abstract

Abstract: 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.

Key words: allochroic silica gel, ZSM-5 zeolite, adsorption capacity, desorption

摘要： 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。

关键词: 变色硅胶, ZSM-5沸石, 吸附量, 脱附

CLC Number:

TK511⁺.3

XIN Feng, YUAN Zhongxian, WANG Wenchao. Adsorption and desorption characteristics of allochroic silica gel and ZSM-5 zeolite to water[J]. Chemical Industry and Engineering Progree, 2015, 34(06): 1730-1736.

辛凤, 苑中显, 王文超. 变色硅胶与ZSM-5沸石分子筛的吸附脱附特性[J]. 化工进展, 2015, 34(06): 1730-1736.

References

[1] Wang D C, Li Y H, Li D, et al. A review on adsorption refrigeration technology and adsorption deterioration in physical adsorption systems[J]. Renewable and Sustainable Energy Reviews, 2010, 14(1):344-353.
[2] 李程, 王如竹, 王丽伟, 等. 不同驱动温度下间歇性太阳能吸附制冰机的实验研究[J]. 化工学报, 2010, 61(s2):112-115.
[3] Choudhury B, Saha B B, Chatterjee P K, et al. An overview of developments in adsorption refrigeration systems towards a sustainable way of cooling[J]. Applied Energy, 2013, 104:554-567.
[4] 王如竹. 吸附式制冷新技术[J]. 化工学报, 2000, 51(4):435-442.
[5] 王如竹, 王丽伟. 低品位热能驱动的绿色制冷技术:吸附式制冷[J]. 科学通报, 2005, 50(2):101-111.
[6] 陈传涓, 王如竹, 夏再忠. 太阳能吸附式空调研发进展与展望[J]. 制冷学报, 2008, 29(4):1-7.
[7] Cui Q, Tao G, Chen H J, et al. Environmentally benign working pairs for adsorption refrigeration[J]. Energy, 2005, 30:261-271.
[8] El-Sharkawy I I, Kuwahara K, Saha B B, et al. Experimental investigation of activated carbon fibers/ethanol pairs for adsorption cooling system application[J]. Applied Thermal Engineering, 2006, 26:859-865.
[9] 卜宪标, 王令宝, 马伟斌. 硅胶孔径对吸附剂吸湿性能及制冷特性的影响[J]. 哈尔滨工程大学学报, 2012, 33(8):989-995.
[10] Aristov Yu I, Restuccia G, Cacciola G, et al. A family of new working materials for solid sorption air conditioning systems[J]. Applied Thermal Engineering, 2002, 22:191-204.
[11] Daou K, Wang R Z, Xia Z Z, et al. Experimental comparison of the sorption and refrigerating performances of a CaCl₂ impregnated composite adsorbent and those of the host silica gel[J]. International Journal of Refrigeration, 2007, 30:68-75.
[12] Gordeeva L G, Gubar A V, Plyaova L M, et al. Composite water sorbent of the salt in silica gel pores type:The effect of the interaction between the salt and the silica gel surface on the chemical and phase compositions and sorption properties[J]. Kinetis Catalysis, 2005, 46:736-742.
[13] 李鑫, 李忠, 刘宇, 等. 不同金属盐改性对硅胶的水蒸气吸附性能影响[J]. 离子交换与吸附, 2005, 21(5):391-396.
[14] Jentys A, Warecka G, Derewinski M, et al. Adsorption of water on ZSM5 zeolites[J]. The Journal of Physical Chemistry, 1989, 93(12):4837-4843.
[15] Dawoud B, Aristov Y. Experimental study on the kinetics of water vapor sorption on selective water sorbents, silica gel and alumina under typical operating conditions of sorption heat pumps[J]. International Journal of Heat and Mass Transfer, 2003, 46:273-281.
[16] Wang L, Chen L, Wang H L, et al. The adsorption refrigeration characteristics of alkaline-earth metal chlorides and its composite adsorbents[J]. Renewable Energy, 2009, 34:1016-1023.
[17] Choma J, Kloske M, Jaroniec M. An improved methodology for adsorption characterization of unmodified and modified silica gels[J]. Journal of Colloid and Interface Science, 2003, 266:168-174.
[18] 杨保义, 张杰. 变色硅胶干燥剂吸湿性能研究[J]. 装备环境工程, 2010, 7(2):32-35.
[19] 陈永. 多孔材料制备与表征[M]. 合肥:中国科学技术大学出版社, 2010:33-38.
[20] Bauer J, Herrmann R, Mitelbach M, et al. Zeolite/aluminum composite adsorbents for application in adsorption refrigeration[J]. International Journal of Energy Research, 2009, 33:1233-1249.