Article Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX
pubs.acs.org/jced
Liquid−Liquid Equilibrium for Ternary System n‑Butanol + n‑Hexane + Ethylene Glycol at 298.15−323.15 K Qingsong Li,* Midong Shi, Liping Wang, Gaoyin He, and Fan Gan The State Key Lab of Heavy Oil Processing, College of Chemical Engineering, China University of PetroleumEast China, Qingdao, Shandong 266580, China ABSTRACT: The liquid−liquid equilibrium (LLE) experiments for n-butanol + nhexane + ethylene glycol were carried out and LLE data were measured at 298.15, 303.15, 308.15, 313.15, and 323.15 K under atmospheric pressure. The analysis results of the effects of n-butanol content and temperature on extraction showed that high nbutanol content was not favorable for extraction, and temperature had little effect on extraction. Moreover, the NRTL and UNIQUAC models were applied to correlate the LLE data, and the correlated data indicated that the UNIQUAC model showed a better correlation performance.
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INTRODUCTION Fischer−Tropsch (FT) synthesis is a kind of indirect coal liquefaction technology, which uses the synthetic gas as raw material. Paraffin hydrocarbons, olefins, and oxygenated compounds are the main products.1 High temperature Fischer−Tropsch (HTFT) synthesis is the key technology of Fischer−Tropsch synthesis. The content of olefins in HTFT synthetic oils is about 25%,2 and the linear α-olefins in olefins are extremely precious chemical raw materials and have high economic value.3−6 Therefore, separation and purification of linear α-olefins from high temperature FT synthetic oil are of great significance. n-Hexene is an important linear α-olefin, which can be used as chemical raw materials of plasticizers, synthetic lubricants, and fatty acids,7−10 and the content of n-hexene in the C6 fraction of HTFT synthetic oils is about 45%.11 Thus, n-hexene is an ideal composition obtained from the high temperature FT synthetic oil. n-Hexene can be separated from the C6 fraction with distillation technology; however, oxygen-containing compounds in the C6 fraction can form an azeotrope with nhexene and other C6 hydrocarbon components.11 Therefore, oxygen-containing compounds should be first removed before separating n-hexene from the C6 fraction. Solvent extraction has good application in the separation of mixtures, such as azeotrope and high boiling components, therefore this method was selected to separate oxygencontaining compounds. n-Butanol is one oxygen-containing compound in the C6 fraction.11 In the present work, it was separated from the C6 fraction with the solvent extraction method. At present, the liquid−liquid equilibria of n-butanol comprise a mostly aqueous system.12−15 What is more, the liquid−liquid phase equilibria of n-butanol in anhydrous systems was also reported. Cai et al.16 investigated the © XXXX American Chemical Society
liquid−liquid equilibrium of n-butanol + n-butyl acetate +1octyl-3-methylimidazolium hexafluorophosphate. Nagata17 reported the liquid−liquid equilibria of acetonitrile + n-butanol + cyclohexane or n-heptane or n-octane at 298.15 K. However, no more data were reported. In C6 fraction of high temperature FT synthetic oils, nhexane is one of the most important substances, which has a relatively high boiling point. Thus, n-hexane was used as a model compound in the present work, and ethylene glycol was selected as an extractant. The liquid−liquid equilibrium data for n-butanol + n-hexane + ethylene glycol were measured at 298.15, 303.15, 308.15, 313.15, and 323.15 K under atmospheric pressure. The extraction performance of ethylene glycol was evaluated by a distribution coefficient and separation factor. Also, the effects of temperature and n-butanol content on the LLE data were analyzed. Moreover, NRTL and UNIQUAC models were applied to correlate the LLE data of this system.
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EXPERIMENTAL SECTION Chemicals. n-Hexane was purchased from Aladdin Industrial Corporation. n-Butanol and ethylene glycol were purchased from Sinopharm Chemical Reagent. The purities of relevant chemicals were checked with Agilent GC6820 gas chromatograph and used without further purification. The detailed information on all chemicals was listed in Table 1. The mass fraction of water in n-butanol and ethylene glycol was lower than 0.1% and 0.7%, respectively. Received: June 23, 2017 Accepted: November 27, 2017
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DOI: 10.1021/acs.jced.7b00577 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
Journal of Chemical & Engineering Data
Article
The LLE data for n-butanol + n-hexane + ethylene glycol at 298.15, 303.15, 308.15, 313.15, and 323.15 K were measured in a 50 mL liquid−liquid equilibrium kettle. The prepared mixture of known mass ratio was first added into the equilibrium cell. Then the cell was sealed by a rubber stopper with a thermometer with a range of 297.15−324.15 K and a standard uncertainty of 0.05 K and fixed on a magnetic stirrer. After heating the equilibrium cell to the desired temperature with an accuracy of 0.1 K, the mixture was stirred vigorously for 3 h. Then, the magnetic stirrer was stopped and the mixture was left undisturbed for 12 h to reach liquid−liquid equilibrium. The samples from n-hexane and ethylene glycol phases were taken out respectively by a microsyringe and analyzed using the above-mentioned gas chromatograph with a thermal conductivity detector (TCD) and Porapak N column (3 mm × 3 m). The injector and detector temperatures were 523 K, and the column temperature was kept at 373 K for 1.0 min, then increased to 523 K at a rate of 20 °C/min and kept for 1.5 min. To ensure the accuracy of measurement, the standard deviation of measurement was less than 1%.
Table 1. Suppliers and Purity of the Chemicals component n-butanol n-hexane ethylene glycol a
CAS Reg. NO.
source
mass fraction purity
analysis method
71-36-3 110-54-3 107-21-1
Sinopharm Aladdin Sinopharm
≥0.9950 ≥0.9900 ≥0.9900
GCa GCa GCa
Gas chromatograph.
Apparatus and Procedure. The apparatus and experimental procedure were described in detail in our previous work.18,19 In the present work, the experiments on the extraction of n-butanol from n-hexane with ethylene glycol as extractant were carried out. The mass concentration range of nbutanol in n-hexane−n-butanol solution was 0−45%, and based on the concentration range of n-butanol in n-hexane-n-butanol solution, the composition of seven phase points was analyzed. The composition of each phase was sequentially measured by changing the mass of n-butanol.
Table 2. LLE Data for n-Butanol (1) + n-Hexane (2) + Ethylene Glycol (3) at Different Temperatures 298.15−323.15 K under 100 kPa Pressurea n-hexane phase (I) x1
x2
x3
x1
x2
x3
D
S
298.15
0.0087 0.0226 0.0411 0.0647 0.0969 0.1393 0.1860 0.0092 0.0236 0.0410 0.0653 0.0985 0.1399 0.1943 0.0098 0.0247 0.0422 0.0679 0.1051 0.1451 0.1993 0.0112 0.0251 0.0457 0.0741 0.1075 0.1505 0.2072 0.0136 0.0300 0.0508 0.0761 0.1102 0.1652 0.2144
0.9913 0.9773 0.9478 0.9216 0.8829 0.8229 0.7560 0.9908 0.9764 0.9550 0.9257 0.8850 0.8286 0.7521 0.9902 0.9753 0.9541 0.9226 0.8729 0.8166 0.7433 0.9834 0.9708 0.9466 0.9131 0.8723 0.8107 0.7283 0.9853 0.9680 0.9439 0.9148 0.8690 0.7947 0.7343
