利用熱分析儀量測對羥基苯甲醛分別與對羥基苯甲酸乙酯、對羥基苯甲酸甲酯以及對羥基苯甲酸丙酯混合之二成份有機混合物的固液相平衡

Solid-Liquid Equilibrium Measurements of 4-Hydroxybenzaldehyde Plus Ethyl-4-hydroxybenzoate or Methyl-4-hydroxybenzoate or Propyl-4-hydroxybenzoate Binary Organic Mixtures Using DSC

袁勝威(Sheng-Wei Yuan)

指導教授 ： 陳延平

國立臺灣大學/工學院/化學工程學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201701491

摘要

在化學工業程序中，大部分的分離操作都需要合適的相平衡條件，才能成功分離或是讓操作程序具有經濟效益。如蒸餾程序中，混合物在液相與氣相的相平衡組成差異性必須要足夠大；萃取則需要液相與液相之間相平衡組成差異大才能進行；結晶程序分離發生在固相與液相之間之相平衡。在設計混合物分離程序前，必須對所選系統的相平衡行為先有了解。

本研究選用三組雙成份混合系統，分別為ethyl-4-hydroxybenzoate (1) + 4-hydroxybenzaldehyde (2)、methyl-4-hydroxybenzoate (1) + 4-hydroxybenzaldehyde (2)、propyl-4-hydroxybenzoate (1) + 4-hydroxybenzaldehyde (2)，進行固液相平衡實驗量測。本研究將藥物以不同莫耳比例混合後填入液態鋁盤，接著送入差式掃描量熱儀進行加熱與數據量測，由儀器所匯出之熱流曲線分析混合物的相變化行為。由不同組成的各種相變化溫度，我們繪製出三組雙成分混合物之固液相平衡圖。從熱流曲線以及相平衡圖觀察本研究的混合行為均屬於簡單共熔相平衡，相圖上具有一個共熔點。所選用的藥品組合均有化學反應中反應物與生成物之關係，因此本研究可提供工業上結晶分離程序之應用。

由量測到之DSC曲線圖以及相平衡圖得知，本研究選擇之混合物相圖均屬於簡單共熔型，具有一個共熔點。由相圖觀察，ethyl-4-hydroxybenzoate (1) + 4-hydroxybenzaldehyde (2) 之共熔組成為x1=0.46，共熔溫度為84.1 oC；混合系統methyl-4-hydroxybenzoate (1) + 4-hydroxybenzaldehyde (2) 之共熔組成為x1=0.46，共熔溫度為84.9 oC，混合系統propyl-4-hydroxybenzoate (1) + 4-hydroxybenzaldehyde (2)之共熔組成為x1=0.59，共熔溫度為71.5 oC

簡單共熔固-液相平衡中，共熔點為純化分離操作之極限，亦是複合相轉化材料最佳的混合比例。除了直接從相圖觀察外，為了減少繁瑣的實驗點量測又不希望失去準確性，本研究利用共熔點比例法推斷所選系統之共熔點組成，結果顯示共熔點轉化比例對組成做圖為線性關係，並且得到的共熔點組成與直接從相圖觀察之結果相近。當混合物組成接近共熔點時，量測到的DSC圖譜之共熔波峰與液化波峰重疊甚多難以區分，實驗誤差大，因此一般希望減少靠近共熔點之實驗量測。由實驗結果得知，即使減少實驗量測點，共熔點轉化比例法也有良好的預測結果。

關鍵字

DSC ； 雙成分混合 ； 固液相平衡 ； 共熔點 ； 對羥基苯甲酸乙酯 ； 對羥基苯甲酸甲酯 ； 對羥基苯甲酸丙酯 ； 4-羥基苯甲醛

並列摘要

In chemical industry, most of the separation operation needs a proper phase equilibrium condition for their success or economical interest. For example, the composition difference between liquid phase and vapor phase most be significant in distillation operation. In extraction, the composition in every liquid phase most differ from each other enough. Crystallization separation occurs with equilibrium between solid phase and liquid phase. Hence, we need to know the phase equilibrium for the design of separation operation.
In this study, we choose three set of binary mixtures to perform the solid- liquid phase equilibrium. They are ethyl-4-hydroxybenzoate (1) + 4-hydroxybenzaldehyde (2)、methyl-4-hydroxybenzoate (1) + 4-hydroxybenzaldehyde (2)、propyl-4-hydroxybenzoate (1) + 4-hydroxybenzaldehyde (2) respectively. We filled the drugs in aluminum plate with different mole fraction and then heat the plate and measured data with differential scanning calorimetry. We analyzed the phase transition behavior with the heat flux curve output by the instrument. We sketch solid-liquid phase equilibrium diagram of these three binary mixtures with the phase change temperature against various compositions. From the heat flux curves and phase diagrams, we found that the system we chose belong to simple eutectic system. There is one eutectic point in each phase diagram. The components of every binary mixture we used have the relationship between reactant and product. This reveals that the experiment result in this study can supply a basis of separation operation design.
The phase diagram of our systems belong to simple eutectic phase equilibrium. The eutectic composition of ethyl-4-hydroxybenzoate (1) + 4-hydroxybenzaldehyde (2) binary mixture is x1=0.46 and eutectic temperature is 84.1 oC. The eutectic composition of methyl-4-hydroxybenzoate (1) + 4-hydroxybenzaldehyde (2) is x1=0.46 and eutectic temperature is 84.9 oC. The eutectic composition of propyl-4-hydroxybenzoate (1) + 4-hydroxybenzaldehyde (2) binary mixture is x1=0.59 and eutectic temperature is 71.5 oC
Eutectic composition is the limit of separation operation and also the favorable composition for complex phase change material. The eutectic phase transition wave and liquidus phase transition wave overlapped a lot when the mixing is near the eutectic composition. It causes the difficulty of the determination of phase transition temperature. In this study, we introduced eutectic transformation fraction to help us to determine eutectic point. The results showed that the eutectic point determined with this method matched the one observed on the phase diagram. And the results revealed that eutectic transformation fraction method can predict the eutectic point well despite the decreasing of experiment data.

並列關鍵字

DSC ； binary mixture ； solid-liquid equilibrium ； eutectic point ； ethyl-4-hydroxybenzoate ； methyl-4-hydroxybenzoate ； propyl-4-hydroxybenzoate ； 4-hydroxybenzaldehyde

參考文獻

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