水與有機蒸氣於聚三氟乙醇基磷氮高分子薄膜中的滲透與吸附特性

吳奇煌

指導教授 ： 孫一明

元智大學/工程學院/化學工程與材料科學學系/碩士(1997年)

摘要

本研究使用聚三氟乙醇基磷氮高分子薄膜針對不同蒸氣之滲透分子，利用擬穩態滲透程序求得滲透係數，並使用微量秤重的方式探討吸附行為以求得溶解度；之後根據溶解擴散模式理論，求得擴散係數。所使用的溶劑可分為水與乙醇(同為極性物質)；以及正己烷、環己烷與苯(非極性且同碳數之碳氫化合物)兩個系列討論。
在吸附實驗中，溶解度隨著溫度上升而下降。由於滲透分子吸附至膜材時，應進入膜材的自由體積，所以滲透分子的溶解度將與滲透分子大小略成反比，在同溫度下之溶解度大小順序為水> 乙醇> 苯> 環己烷> 正己烷。利用van't Hoff eq. 求得水、乙醇、正己烷、環己烷與苯的吸附熱分別為-25.5, -22.4, -21.4, -16.9與-33.8 KJ/mol。
在滲透實驗中，滲透係數與擴散係數隨著活性係數增加而以指數形式增加；隨著溫度上升，滲透係數與擴散係數皆增加。PTFEP膜材對於不同滲透分子的滲透係數於同溫度與活性係數時的大小為：水> 乙醇> 苯> 正己烷> 環己烷。影響擴散行為的因素為滲透分子的碰撞直徑，當滲透分子碰撞直徑上升時，擴散係數隨之下降；根據Arrhenius eq.求得水、乙醇、正己烷、環己烷與苯滲透活化能為24.2, 29.4, 48.9, 54.1與38.4 KJ/mol與擴散活化能為49.7, 51.8, 70.3, 70.9與72.2 KJ/mol。

關鍵字

聚三氟乙醇基磷氮高分子 ； 滲透係數 ； 溶解度 ； 擴散係數 ； 吸附熱 ； 滲透活化能 ； 擴散活化能

並列摘要

The permeation and sorption properties for water, ethanol, n-hexane, cyclohexane, and benzene vapors in the poly[bis(trifluoroethoxy)-phosphazene] (PTFEP) membrane have been studied. The permeability was determined from the pseudo-steady-state permeation experiment, the solubility was measured by a micro-gravimetrical method, and the diffusivity was calculated by using the solution-diffusion model for those vapors in the PTFEP membrane.
The solubility increases with temperature for all the vapors. The order of the solubility for those vapors in PTFEP is: water > ethanol > benzene > cyclohexane > n-hexane. The larger the permeate size (Van der Waals volume) is, the lower the solubility is. It is speculated that the size of the permeate affect the magnitude of the solubility because the limited amount of free-volume in the polymer membrane may determine the number of permeate molecules sorbed. The heat of sorption for water, ethanol, n-hexane, cyclohexane, and benzene vapors in PTFEP are -25.5, -22.4, -21.4, -16.9, and -33.8 KJ/mol, respectively.
The permeability and diffusivity increase with the vapor activity and increase with temperature. The order of the permeability for those vapors through the PTFEP membrane is: water > ethanol > benzene > n-hexane > cyclohexane. It is speculated that the diffusivities for those permeates are influenced by the their collision diameters. As the collision diameter increases, the diffusivity decreases. The activation energies of permeation and diffusion for water, ethanol, n-hexane, cyclohexane and benzene vapors through the PTFEP membrane are 24.2, 29.4, 48.9, 54.1 and 38.4 KJ/mol and 49.7, 51.8, 70.3, 70.9 and 72.2 KJ/mol, respectively.

並列關鍵字

poly[bis(trifluoroethoxy)-phosphazene] ； permeability ； solubility ； diffusivity ； heat of sorption ； activation energies of permeation ； activation energies of diffusion

參考文獻

Allcock, H. R. et al., "Gas Permeation and Selectivity of Poly(organophazene)Membrane," Macromolecules, 26, 1493-1502 (1993)

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Allcock, H. R., R. L. Kugel, and K. J. Valan, "Phosphonitrilic Compounds. VI. High Molecular Weight Poly(alkoxy- and aryloxy-phosposphazenes)," Inorganic Chemistry, 5, 1709 (1966)

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