Eng. Japan, 16, 324 (1983). 38, 567 (1983). ll) Taylor,G. I. andA. D. McEwan: /. FluidMech., 22, 1 (1965). 13) Yoshida, F., M. Yamaguchi and T. Katayama: /. Chem, Eng. 12) Terasawa, H., Y. H. Mori andK. Komotori: Chem. Eng. ScL, Japan, 19, 1 (1986). HIGH-PRESSURE TERNARY LIQUID-LIQUID EQUILIBRIA FOR THE SYSTEMS OF WATER, ALCOHOL (1-PROPANOL, 1-BUTANOL AND 1-PENTANOL) AND 1,1-DIFLUOROETHANE AT 323.2K TAKASHI NAKAYAMAAND HIROSHI SAGARA Research & Development Div., JGC Corporation, Yokohama 232 KUNIO ARAI AND SHOZABUROSAITO Department of Chemical Engineering, Tohoku University, Sendai 980 Key Words: Liquid-Liquid Equilibrium, 1,1-Difluoroethane, 1-Propanol, 1-Butanol, 1-Pentanol, Water, Ethanol, Fusel Oil, Distribution Coefficient For the separation of fusel oil from low-concentration fermentation broths, ternary liquid-liquid equilibria at 323.2 K were measured for the systems of water and 1,1-difluoroethane with alcohols (l-propanol, 1-butanol and 1- pentanol). The liquefied gas 1,1-difluoroethane can achieve much higher distribution coefficients of l-propanol, 1- butanol and 1-pentanol than ethanol. Therefore, l-propanol, 1-butanol and 1-pentanol will be selectively removed from low-concentration ethanol aqueous solutions with liquefied 1,1-difluoroethane at low solvent ratios. The liquid-liquid equilibrium data were correlated by the UNIQUACand NRTLequations. The UNIQUAC equation gave better correlation of the experimental data than did the NRTLequation. However, the two-phase regions estimated by the UNIQUACequation were larger than the experimental results for the systems of water + l-propanol + 1,1-difluoroethane and water + 1-pentanol + 1,1-difluoroethane. we selected 1-propanol (PrOH), 1-butanol (BuOH) Introduction and 1-pentanol (AmOH) as representative alcohols In the refining of ethanol from low-concentration contained in fusel oil, and measured ternary liquid- fermentation broths, ethanol enrichment and the re- liquid equilibria for the systems H2O-PrOH-DFE, moval of impurities such as fusel oil from ethanol are H2O-BuOH-DFE and H2O-AmOH-DFE. The mea- usually accomplished by energy-intensive distillation. sured alcohol distribution coefficients are compared To find an alternative gas-liquid or liquid-liquid with the ethanol distribution data reported in a extraction process, manyresearchers have studied the previous work.7) In addition, the liquid-liquid dehydration of ethanol with supercritical ethane,6) equilibrium data are correlated with the UNI- supercritical or liquefied carbon dioxide4'9'1M3) and QUAC,1} NRTL10) and LEMF (local effective mole liquefied l,l-difluoroethane.7) However, the sepa- fraction equation)5} solution models. ration of impurities from dehydrated or aqueous ethanol has not yet been reported. 1. Experimental In the present work, we selected liquefied 1,1- The static method was used for obtaining high- difluoroethane (DFEhereafter) as an extraction sol- pressure liquid-liquid equilibrium data. The experi- vent for the separation of fusel oil from ethanol mental apparatus and procedure are almost the same aqueous solutions, since it is immiscible in water and as reported in a previous paper.7) A schematic dia- is expected to show higher selectivity for the more gram is shown in Fig. 1. Liquid samples are with- lipophilic fusel oil than ethanol. DFE also has low drawn from the equilibrium cell ®to the samplers toxicity. To establish a basis for fusel oil extraction, (2) through capillary tubes and then flushed to the evacuated sampling lines. The pressure decrease in Received June 29, 1987. Correspondence concerning this article should be addressed to T. Nakayama. the equilibrium cell that occurs during sampling is VOL. 21 NO. 2 1988 129 Fig. 1. Schematic diagram of experimental apparatus automatically compensated for by the action of the diaphragm (3) connected to both equilibrium cell and buffer tank ®. Heavier polar componentstended to condense in the samplers and therefore we found it necessary to wrap the samplers with heat tapes. The present experimental procedure was checked by measuring binary liquid-liquid equilibria for the H2O-BuOH and H2O-AmOHsystems at 323.2 K. As shown in Fig. 2, the binary mutual solubility for both systems (solid lines) increases slightly with increasing pressure. The present measurements are in good agreement with the literature values.2'3'8'12* Materials used DFE having a quoted purity of 99.7+mol% was supplied by Daikin Ind. Co., Ltd. Special reagent-grade alcohols were supplied by Mole traction ot BuOH or AmOH WakoPure Chemical Ind. Ltd. and were used without further purification. Gas chromatograph analysis Fig. 2. Liquid-liquid equilibria for the H2O-BuOH and H2O-AmOHsystems at 323.2K. Experimental data for the with a thermal conductivity detector indicated the H2O-BuOH system: V, Fuehner;2) A, Hill et ai;3) D, purities to be 99.9mol%, 99.9mol% and 98.5mol% Othmer et al.;8) O, this work. Experimental data for the for 1-propanol, 1-butanol and 1-pentanol, respec- H2O-AmOHsystem: A, data smoothed by S^rensen et al.;12) tively. Water content of reagent 1-propanol, 1-bu- #, this work tanol and 1-pentanol was 0.1, 0.1 and 1.5mol%, respectively. Water was ion-exchanged and purified has two immiscible binary pairs and no plait point. As by distillation. DFEwas passed through a molecular the alcohol carbon numberincreases, the slopes of tie sieve 5A bed for calibration of the gas chromato- lines become greater. graph, but was otherwise used without purification 2.1 Extraction of fusel oil components from ethanol in the experimental measurements. aqueous solutions As shown in Fig. 6, the measured alcohol distri- 2. Results and Discussion bution coefficients are compared with those for the Tie line data are listed in Tables 1, 2 and 3. water-ethanol-DFE system.7) The plait points esti- Representative liquid-liquid equilibria at 323.2 K are mated by Treybal's method14) for the H2O-PrOH- shown in Figs. 3, 4 and 5, respectively for the H2O- DFE and H2O-EtOH-DFE systems are given in PrOH-DFE, H2O-BuOH-DFE and H2O-AmOH- Table 4. The alcohol distribution coefficient increases DFE systems at 1.32MPa. The H2O-PrOH-DFE as the alcohol carbon number is raised. This is to be system is classified as liquid-liquid equilibrium Type expected since alcohols with higher carbon numbers 1,15) which has one immiscible binary pair and a plait are more lipophilic in nature. On the other hand, with point, while the H2O-BuOH-DFE and H2O- increasing pressure the solute distribution coefficients AmOH-DFEsystems are classified as Type 2, which increase, except those for ethanol. An increase in 130 JOURNAL OF CHEMICAL ENGINEERING OF JAPAN Table 1. Liquid-liquid equilibria for the H2O-PrOH-DFE system at 323.2K Mole fraction [-] Pressure TT . , tm-t- . , H2O-nch phase DFE-nch phase H2O PrOH DFE H2O PrOH DFE 1.32 0.9960 0. 0.0040* 0.0117 0. 0.9883* 0.9776 0.0174 0.0050 0.0289 0.0323 0.9388 0.9582 0.0363 0.0055 0.0790 0.1295 0.7915 0.9490 0.0450 0.0060 0.2385 0.2577 0.5038 0.9452 0.0483 0.0065 0.3863 0.3116 0.3021 0.9387 0.0543 0.0070 0.5036 0.3136 0.1828 6.08 0.9958 0. 0.0042* 0.0145 0. 0.9855* 0.9783 0.0166 0.0051 0.0303 0.0334 0.9363 Fig. 3. Liquid-liquid equilibrium for the H2O-PrOH- 0.9604 0.0341 0.0055 0.0808 0.1284 0.7908 DFE system at 323.2K and 1.32MPa 0.9484 0.0453 0.0063 0.2436 0.2572 0.4992 0.9444 0.0491 0.0065 0.3928 0.3121 0.2951 0.9239 0.0665 0.0096 0.6211 0.2700 0.1089 * H2O-DFE binary mutual solubility data at 323.2K were reported in a previous work.7) Table 2. Liquid-liquid equilibria for the H2O-BuOH-DFE system at 323.2K Mole fraction [-] Pressure . ___ . TMP1 H2O-nch phase DFE-nch phase H2O BuOH DFE H2O BuOH DFE 1.32 0.9917 0.0040 0.0043 0.0215 0.0317 0.9468 0.9877 0.0080 0.0043 0.0734 0.1323 0.7943 0.9865 0.0091 0.0044 0.2021 0.2734 0.5245 Fig. 4. Liquid-liquid equilibrium for the H2O-BuOH- 0.9850 0.0112 0.0038 0.3638 0.4131 0.2231 DFE system at 323.2K and 1.32MPa 0.9838 0.0161 0. 0.5497 0.4503 0. Table 3. Liquid-liquid equilibria for the H2O-AmOH-DFE system at 323.2K Mole fraction [-] H2O-rich phase DFE-rich phase H2O AmOH DFE H2O AmOH DFE 1.32 0.9953 0.0007 0.0040 0.0158 0.0120 0.9722 0.9942 0.0019 0.0039 0.0776 0.1292 0.7932 0.9940 0.0022 0.0038 0.2074 0.2723 0.5203 0.9935 0.0028 0.0037 0.2280 0.3175 0.4545 0.9959 0.0041 0. 0.3923 0.6077 0. 6.08 0.9952 0.0008 0.0040 0.0180 0.0130 0.9690 0.9940 0.0019 0.0041 0.0790 0.1338 0.7872 0.9939 0.0022 0.0039 0.2020 0.2818 0.5162 Fig. 5. Liquid-liquid equilibrium for the H2O-AmOH- 0.9938 0.0026 0.0036 0.2351 0.3154 0.4495 DFE system at 323.2K and 1.32MPa 0.9958 0.0042 0. 0.3989 0.6011 0. ecules in the liquefied gas phase. pressure causes a larger increase in the liquid density Selectivity curves for the water-alcohol-DFE sys- of the liquefied gas phase than in that of the water tems at 323.2K and at pressures of 1.32, 6.08 and phase.