| Abstract: | 摘要 對於一些高純度化學品的分離或是廢水處理程序方面的設計，皆須仰賴稀釋端的汽液相平衡數據，而無限稀釋活性係數則是屬於稀釋端汽液相平衡數據裡面相當重要的一環，當有了無限稀釋活性係數值後，可用來求解活性係數模式中之參數，進而預測整個濃度範圍的汽液相平衡，除此之外如亨利常數，分配係數，或是用於萃取蒸餾、共沸蒸餾、萃取程序中質量分離劑(mass separating agent)之選擇率，以及無限稀釋下之部份莫耳過剩焓值(partial molar excess enthalpy, )等分離製程開發設計所需資料皆可隨之求得，故稀釋端與無限稀釋活性係數的數據有其重要性。 本研究以丙酮-水當作吾人測試之系統，利用頂空進樣系統(headspace sampling)為理論基礎而發展出來的方法─如equilibrium headspace sampling (EHS)方法phase ratio variation (PRV)方法及multiple headspace extraction (MHE)等方法來量測稀釋端相平衡數據與無限稀釋活性係數，並與文獻中其他方法所得的實驗值作比較，另外也探討各個方法的優缺點比較。 由丙酮-水當作測試系統來看，雖然文獻中丙酮在水中之無限稀釋活性係數值差異頗大，但本研究實驗結果顯示在三個溫度下(35℃,45℃,100℃)使用頂空進樣系統來量測稀釋端相平衡數據與無限稀釋活性係數和使用PRV方法及MHE方法得到無限稀釋活性係數值均相當接近，同時其對溫度的相依性皆有相當一致的關係( ─EHS：4.946 kJ/mol , PRV：4.515 kJ/mol , MHE：4.673 kJ/mol)，整體而言，以本研究所使用的方法來量測稀釋端汽液相平衡數據，配以傳統汽液相平衡裝置(如動態循環汽液相平衡裝置)採集之有限濃度平衡數據，將有助於吾人對各系統汽液相平衡現象有更完整的了解。
Abstract In the design of separation processes involving high-purity chemicals or design of waste water treatment equipment, it is oftentimes necessary to have dilute-end vapor liquid equilibrium data available in advance. On the other hand, data of activity coefficient at infinite dilution is an important part of dilute-end vapor liquid equilibrium data. When available, it can be used to solve for parameters in many activity coefficient models which may in turn determine the vapor liquid equilibrium behavior for the entire concentration range. In addition, key information, such as Henry’s constant, partition coefficient, selectivity of mass separating agents being used in extractive distillation, azeotropic distillation, or extraction processes, and partial molar excess enthalpy at infinite dilution, needed in designing and developing separation processes can be subsequently obtained. Binary acetone-H2O system has been used as the test system for this study. Specifically, three headspace sampling-based experimental methods — equilibrium headspace sampling method (EHS), phase ratio variation method (PRV), and multiple headspace extraction method (MHE) were employed to measure dilute-end vapor liquid equilibrium data and infinite-dilution activity coefficient data. They have been compared with literature data. Advantages and disadvantages of these methods were also looked into. Our findings showed that it was feasible to use such methods to properly measure dilute-end and infinitely dilute vapor liquid equilibrium data. The infinite-dilution activity coefficient values taken at three temperature levels by using the PRV and MHE methods turned out to be very consistent. Even though there were some differences between the experimental and scattered literature data, the dependence of experimental infinite-dilution activity coefficient data for three different methods with respect to temperature was in very satisfactory agreement. It is clear that the dilute-end equilibrium data generated by the methods, when combined with finite-concentration vapor liquid equilibrium data, will aid in a full understanding of the vapor liquid equilibrium behavior. |
