以締合結晶法分離間氯酚與對氯酚之沸點相近混合物

Separating Close-Boiling Mixtures of m-Chlorophenol and p-Chlorophenol by Adductive Crystallization

何澤民(Tze-Min Her)

指導教授 ： 李亮三

國立中央大學/工學院/化學工程與材料工程學系/博士(2005年)

摘要

本研究嘗試以固體消失法，有系統地量測兩個三成分系統及五個二成分系統之熔點，建立固液平衡相圖。並嘗試使用苯胺與第三丁醇為締合劑，以締合結晶法將沸點相近之間氯酚 (沸點489.2 K) 與對氯酚 (沸點490.2 K) 之共熔混合物完全分離。
量測結果顯示，間氯酚與對氯酚之二成分系統具有一個共熔點。這顯示以結晶法無法完全分離間氯酚與對氯酚之混合物。
苯胺+間氯酚與苯胺+對氯酚之二成分系統具有兩個共熔點及一個合熔點。而且合熔點均於苯胺之莫耳分率為0.5時發生，可見合熔物之型式應為AB或AC (A代表苯胺；B代表間氯酚；C代表對氯酚)。
第三丁醇+間氯酚與第三丁醇+對氯酚之二成分系統具有兩個共熔點及一個合熔點。而且合熔點均於第三丁醇之莫耳分率為0.67時發生，可見合熔物之型式應為A2B或A2C (A代表第三丁醇；B代表間氯酚；C代表對氯酚)。
苯胺+間氯酚+對氯酚之三成分系統具有兩個共熔點及一個合熔點。而且合熔點均於苯胺之莫耳分率為0.5時發生，可見合熔物應為AB與AC之混合物。根據此三成分系統之固液平衡數據，使用苯胺為締合劑，我們可以利用締合結晶法，設計兩種分離程序，將間氯酚與對氯酚之共熔混合物完全分離。
第三丁醇+間氯酚+對氯酚之三成分系統具有兩個共熔點及一個合熔點。而且合熔點均於第三丁醇之莫耳分率為0.67時發生，可見合熔物應為A2B與A2C之混合物。根據此三成分系統之固液平衡數據，使用第三丁醇為締合劑，我們可以利用締合結晶法，設計一種分離程序，將間氯酚與對氯酚之共熔混合物完全分離。
所有實驗數據均可用Ott and Goates 經驗式迴歸。迴歸結果顯示，熔點計算值與實驗值間之平均絕對誤差，大部份在0.3 K以內，少數介於0.3至0.9 K之間。由此觀之，Ott and Goates 經驗式足以作為數據內插之用。

關鍵字

none

並列摘要

In this study, the solid-liquid equilibrium (SLE) data of two ternary systems and their constituent binary systems, aniline + m-chlorophenol + p-chlorophenol; and tert-butanol + m-chlorophenol + p-chlorophenol, were experimentally investigated by means of solid-disappearance method. We also try to use aniline and tert-butanol as adductive agent to separate the eutectic and close-boiling mixture of m-chlorophenol (b.p. 489.2 K) and p-chlorophenol (b.p. 490.2 K).
The binary system m-chlorophenol + p-chlorophenol was observed to exhibit one eutectic point. This means that completely separating m-chlorophenol from p-chlorophenol by simple crystallization is absolutely impossible.
While each of the binary pairs of aniline + m-chlorophenol and aniline + p-chlorophenol exhibits two eutectic points and one congruent point at aniline mole fraction of 0.5, i.e. a congruent complex in formula AB or AC is formed during freezing (A stands for aniline; B stands for m-chlorophenol; C stands for p-chlorophenol).
However the tert-butanol + m-chlorophenol and tert-butanol + p-chlorophenol mixtures behave slightly differently, each exhibiting two eutectic points and one congruent point near tert-butanol mole fraction of 0.67. This suggests that a congruent complex in formula A2B or A2C is formed during freezing (A stands for tert-butanol; B stands for m-chlorophenol; C stands for p-chlorophenol).
As for the ternary mixtures of aniline + m-chlorophenol + p-chlorophenol with designated mole ratios of m-chlorophenol to p-chlorophenol (pseudo binary systems), they all possess two eutectic points and one congruent point at aniline mole fraction of 0.5. It implies that the mixtures of congruent complexes of AB and AC are formed during freezing. Based on the information presented in the ternary phase diagram and using aniline as an adductive agent, two conceptually feasible processes of separating the eutectic mixture of m-chlorophenol + p-chlorophenol are proposed.
Another systematic pseudo binary systems of tert-butanol + m-chlorophenol + p-chlorophenol were investigated too. They all exhibit two eutectic points and one congruent point near tert-butanol mole fraction of 0.67. It suggests that the mixtures of congruent complexes of A2B and A2C are formed during freezing. Based on the information presented in the ternary phase diagram and using tert-butanol as an adductive agent, one conceptually feasible process of separating the eutectic mixture of m-chlorophenol + p-chlorophenol can be developed.
The Ott and Goates’ equation can be used to fit all the experimental data. Most of the AAD’s are less than 0.3 K, except very few AAD’s that lie between 0.3 K and 0.9 K. Generally speaking, the Ott and Goates’ equation is quite satisfactory for interpolation purposes.

並列關鍵字

chlorophenol ； adductive

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