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Liquid–liquid and liquid–liquid equilibrium for ternary system water–acetonitrile–cyclohexene at 298.15 K
Fluid Phase Equilibria 408 (2016) 10–14
Contents lists available at ScienceDirect
Fluid Phase Equilibria j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / fl u i d
Liquid–liquid and liquid–liquid equilibrium for ternary system water– acetonitrile–cyclohexene at 298.15 K Anastasia Frolkova* , Darya Zakharova, Alla Frolkova, Stanislav Balbenov Department of Chemistry and Technology of Basic Organic Synthesis, Lomonosov Moscow State University of Fine Chemical Technology, Vernadskogo prospect 86, Moscow 119571, Russia
A R T I C L E I N F O
A B S T R A C T
Article history: Received 18 February 2015 Received in revised form 16 June 2015 Accepted 25 June 2015 Available online 2 July 2015
Liquid–liquid (LLE) and liquid–liquid equilibrium (LLLE) data for the ternary system water–acetonitrile– cyclohexene were obtained at 298.15 K and 99.06 kPa. The results of mathematical modelling of LLE and LLLE with the use of the NRTL and UNIFAC models were compared. Both models provide a good description of vapour–liquid equilibrium (VLE). It was determined that the experimental and calculated (NRTL) data are in good agreement, and it was demonstrated that the UNIFAC model could not be used for studying LLE and LLLE in the considered system. ã 2015 Elsevier B.V. All rights reserved.
Keywords: Liquid–liquid equilibrium Liquid–liquid equilibrium Azeotropic systems
1. Introduction The investigation of phase equilibrium in multicomponent multiphase systems is a complex task. One of the most effective methods of studying these is through mathematical modelling. There are several research studies devoted to development of algorithms for LLE and LLLE calculation, correlation and prediction [1–3]. The authors agree on the use of the NRTL model for the description of the phase equilibrium of multiphase systems. The parameters of the NRTL model should give both correct qualitative reproduction of the thermodynamic behaviour of the system and quantitative agreement with experimental data. However, experimental LLLE data are scarce compared with the VLE and LLE data. An analysis of the literature revealed approximately 60 experimentally-studied ternary systems. Currently, the systems most investigated are those containing water [4–12]. At the same time, the research of splitting systems is highly promising from the point of view of separation processes. Recently, the number of works devoted to development of three-liquidphase extraction for the separation of complex mixtures has increased [13–19]. The use of the splitting effect is analogous to separation processes based on distillation methods [20,21] because it is spontaneous and does not require additional energy
* Corresponding author. E-mail address: [email protected] (A. Frolkova). http://dx.doi.org/10.1016/j.fluid.2015.06.039 0378-3812/ ã 2015 Elsevier B.V. All rights reserved.
costs. Thus, the investigation of the liquid–liquid envelope is necessary for the design of separation processes. In the present study, the water–acetonitrile–cyclohexene system, which is an industrially important system for the synthesis of cyclohexanone [22]), was chosen as the object of a splittingdiagram study. There are number of experimental studies that present VLE and LLE data for the binary constituents of a ternary system. The binary systems water–acetonitrile and water–cyclohexene contain azeotropes with minimum boiling temperatures [23–27]. The water–acetonitrile system is homogeneous, and the other two are heterogeneous [28–29]. An analysis of the published data indicates that there are no experimental data for the liquid–liquid and liquid–liquid equilibrium in the considered ternary system. This work presents the results of our experimental study of LLE and LLLE in the water– acetonitrile–cyclohexene system at 298.15 K and 99.06 kPa. 2. Experimental 2.1. Materials The purities of the chemicals (see Table 1) were verified chromatographically and in terms of refraction indexes. All physicochemical constants of the pure substances were determined to be in agreement with the data in the literature [30]. The cyclohexene was purified by distillation and chromatographic analysis indicated that its purity practically did not change. The water was double-distilled.
A. Frolkova et al. / Fluid Phase Equilibria 408 (2016) 10–14 Table 1 The purities of the chemicals.
Table 3 Experimental (liquid + liquid) data for the system water–acetonitrile–cyclohexene for mole fractions (x) at temperature T = 298.15 K and pressure p = 99.06 kPa.a
Substance
Purity, mass fraction
Manufacturer
Water Acetonitrile Cyclohexene
0.999 0.999 0.990
– LAB-SCAN analytical sciences ACROS ORGANICS
Composition of coexisting phases, mole fraction
Table 2 Experimental (liquid + liquid + liquid) data for the system water–acetonitrile– cyclohexene for mole fractions (x) at temperature T = 298.15 K and pressure p = 99.06 kPa.a Composition of coexisting phases, mole fraction Phase 1
11
Phase 2
Phase 3
Water
Acetonitrile
Water
Acetonitrile
Water
Acetonitrile
0.894
0.103
0.321
0.620
0.009
0.116
Standard uncertainties are u(T) = 0.3 K, u(x) = 0.0032, and u(p) = 0.4 kPa.
2.2. Methods The LLE and LLLE were investigated using gas chromatography. Ternary mixtures of known composition within the splitting region were prepared by the gravimetric method using a ScienTech SA210 analytical balance with an accuracy of 0.0001 g. It was considered that the phase equilibrium is reached when there was a full distribution of phases among themselves. After phase equilibrium was reached the phases were separated using a
Phase 1
Phase 2
Water
Acetonitrile
Water
Acetonitrile
0.968 0.931 0.851 0.013 0.017
0.031 0.068 0.148 0.135 0.136
0.013 0.004 0.338 0.017 0.151
0.096 0.099 0.602 0.720 0.728
Standard uncertainties are u(T) = 0.3 K, u(x) = 0.0032, and u(p) = 0.4 kPa
separatory funnel and were analysed by gas chromatography. A LChM-80 chromatograph (Russia) was used with two packed columns, a Porapak Q (3 m) and a Porapak P (1 m), both with a 3 mm i.d. The column and injector temperatures were 453 K, and the detector temperature was 473 K. Notably good peak separation was achieved under these conditions. A method of internal normalization and relative calibration was used to calculate the compositions of the equilibrium liquid phases. Acetonitrile was used as the linking component. The uncertainty in the mole fraction was usually less than 0.003. At least three analyses were made of each liquid composition. 2.3. Results and discussion Experimental data on LLLE and LLE in system water– acetonitrile–cyclohexene are listed in Tables 2 and 3. A three-
Fig. 1. Splitting diagram of the water–acetonitrile–cyclohexene ternary system.
12
A. Frolkova et al. / Fluid Phase Equilibria 408 (2016) 10–14
Table 4 The NRTL binary interaction parameters for system water (1)—acetonitrile (2)— cyclohexene (3).
Aij Aji Bij(K) Bji(K) Cij
12
13
23
0.0 0.0 665.1194 183.5932 0.2858
8.2209 -2.9573 -27.1069 2317.7234 0.2
0.0 0.0 360.4846 555.6110 0.3
liquid-phase triangle and the binodal curves constructed on the basis of experimental data are presented in Fig. 1. The splitting
diagram contains one three-phase region, two two-phase splitting regions of the open type and one of the closed type. The next step was the mathematic modelling of the LLE and LLLE with the use of the correlating NRTL model and the predicting UNIFAC model. The binary interaction parameters for NRTL model are given in Table 4: X 0 1 X xi t ji Gji xm t mj Gmj X xj Gij B C j Bt ij mX C X ð1Þ þ lng i ¼ X @ A xk Gki x G x G k kj k kj j k
k
k
Table 5 Results of comparing the experimental data from the literature and the calculated azeotropic data (composition and boiling point) for the ternary system water–acetonitrile– cyclohexene at 101.30 kPa. Azeotrope
Literature data
Calculated data UNIFAC
Water– acetonitrile Water–cyclohexene Acetonitrile– cyclohexene Water–acetonitrile– cyclohexene
NRTL
Concentration of the first (second) component, mole fraction
G,K
0.319 0.309 –
349.35 0.329 343.95 0.319 – 0.495
348.48 0.324 343.93 0.319 338.16 0.489
349.94 343.90 338.73
–
–
333.96 0.195 (0348)
334.52
Concentration of the first (second) component, mole fraction
0.198 (0359)
G, K
Concentration of the first (second) component, mole fraction
Fig. 2. Distillation diagram of the water–acetonitrile–cyclohexene ternary system at 101.30 kPa.
G, K
A. Frolkova et al. / Fluid Phase Equilibria 408 (2016) 10–14
13
Table 6 Calculated data values of the LLLE of ternary system water–acetonitrile–cyclohexene at 298.15 K. Composition of coexisting phases, mole fraction Phase 1
Calculated (UNIFAC) RMSD = 7.67 % Calculated (NRTL) RMSD = 3.69 %
Phase 2
Phase 3
Water
Acetonitrile
Water
Acetonitrile
Water
Acetonitrile
0.881
0.117
0.155
0.700
0.02
0.118
0.882
0.117
0.259
0.672
0.004
0.095
Table 7 The calculated data values of the LLE of the water–acetonitrile–cyclohexene ternary system at 298.15 K. Composition of coexisting phases, mole fraction Calculated (UNIFAC)
Calculated (NRTL)
Phase 1
Phase 2
Phase 1
Phase 2
Water
Acetonitrile
Water
Acetonitrile
Water
Acetonitrile
Water
Acetonitrile
0.956 0.863 0.006 0.928 0.022 RMSD = 3.55%
0.043 0.136 0.151 0.071 0.124
0.016 0.210 0.023 0.018 0.161
0.041 0.722 0.737 0.069 0.691
0.957 0.848 0.0013 0.928 0.004 RMSD = 1.69%
0.042 0.147 0.133 0.071 0.102
0.003 0.340 0.025 0.003 0.173
0.040 0.608 0.765 0.068 0.725
where Gij = exp (aijt il);
t ij ¼ aij þ
liquid and liquid–liquid equilibria of the considered system. Moreover, the UNIFAC model gives a splitting region in the binary constituent water–acetonitrile, although it is well-known [24–25] that this system is homogeneous.
bij þ eij lnT þ f ij T; T
aij = cij+dij(T 273.15); and t ii = 0; Gii = 1; .
3. Conclusions
The approach to the UNIFAC method was developed in [31]: lng ¼ lng ci þ lng ri ;
ð2Þ
i i Z i i þ 1 ln þ 1 ; lng ¼ ln i i 2 ui ui where
S
Fi ¼ xi ri =
P
ng
xj rj ui ¼ xi z=2qi Sxj z=2qj ri Sk vki Rk qi ¼
ng k vki Q k :
The modelling was based on the UNIFAC parameters presented in [32,33]. A UNIFAC model simulation generally leads to results that are in good agreement with experimental data. Both models give a good description of the vapour–liquid equilibrium in the considered ternary system. The results of comparing the experimental data from the literature and the calculated azeotropic data (composition and boiling point) are presented in Table 5. The diagram of distillation lines is presented in Fig. 2. The diagram contains three binary and one ternary azeotrope with three distillation regions. The root-mean-square deviation (RMSD) of the phase composition was also calculated: M
RMSD ¼ 100
r n1 ðxexp ijk
S S S
k¼1 j¼1 i¼1
xcalc Þ2 ijk
rðn 1Þ
Experimental data for the LLE and LLLE were obtained for the water–acetonitrile–cyclohexene ternary system at 298.15 K and 99.06 kPa. The comparison of the experimental data with the values calculated on the basis of the NRTL model indicated that the parameters presented can be employed for studying the phase equilibrium of the considered system and for development of a flow-sheet for its separation. At the same time, we cannot recommend using the UNIFAC model for this purpose. Our research indicates that only experimentally confirmed parameters of a chosen model can be used for studying the phase equilibrium of the system. Acknowledgments This work was carried out according to the stated task of the Russian Ministry of Education and Science #10.99.2014/K. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.fluid.2015.06.039.
!1=2 ;
where xexp and xcalc are the experimental and calculated molar ijk ijk fraction component i in phase j on tie-line k; and M is the number of tie-lines. The calculated values (at 298.15 K) and the RMSD are presented in Tables 6 and 7. The simulation on the basis of NRTL model leads to results that are in good agreement with experimental data. However, the UNIFAC model cannot be recommended for studying the liquid–
References [1] Roumiana P. Roumiana Stateva, Georgi St. Cholakov, A. Anatolii Galushko, William A. William Wakeham, A powerful algorithm for liquid–liquid equilibria predictions and calculations, Chem. Eng. Sci. 55 (2000) 2121–2129. [2] F. Denes, P. Lang, M. Lang-Lazi, Liquid–liquid equilibrium calculations. Distillation and absorption, in: E. Sorensen (Ed.), Institution of Chemical Engineers Symposium Series No. 152, Rugby, UK, 2006, pp. 877–890. [3] A.W. Frencis, Ternary systems of liquid carbon dioxide, J. Phys. Chem. 58 (212) (1954) 1099. [4] P. Bocko, Equilibrium of three liquid phases in water–acetonitrile–benzene-nhexane mixtures at 65 C, Fluid Phase Equilib. 4 (1980) 137–150.
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[5] H. Van Bochove Gerard, J.P. Krooschof Gerard, W. De Loos Theo, Two- and three-liquid phase equilibria in the system water + 2heptanone + caprolactam + ammonium sulfate: experiments and modelling, Fluid Phase Equilib. 194 (2002) 1029–1044. [6] Zhou Huan, Gerard Van Bochove, Theo De Loos, Three-liquid phase equilibria in water + benzene + caprolactam + (NH4)2SO4 mixtures, AIChE J. 49 (3) (2003) 745–752. [7] J.G. Andersen, N. Koak, T.W. DeLoos, Influence of pressure on the LLLE in water + n-alkyl polyoxyethylene ether + n-alkane systems, Fluid Phase Equilib. 2 (163) (1999) 259–273. [8] H.Y. Hou, X.Q. An, W.G. Shen, Three-liquid phases equilibria for the quaternary system water plus formamide plus cyclohexane plus diethylene glycol monobutyl ether near the tricritical point, J. Chem. Eng. Data 50 (4) (2005) 1308–1312. [9] V.P. Sazonov, A.G. Sarkisov, About the equilibrium of three liquid in ternary systems. I. Systems furfural + cyclohexane + water and aniline + heptane + water, Russ. J. Phys. Chem. 42 (8) (1968) 2066–2070 (in Russian). [10] V.P. Sazonov, About the equilibrium of three liquid in ternary systems. II. System nitromethane + heptanol + water, Russ. J. Phys. Chem. 42 (12) (1968) 3094–3096 (in Russian). [11] V.P. Sazonov, About the equilibrium of three liquid in ternary systems. III. System benzyl alcohol + heptane + water, Russ. J. Phys. Chem. 1 (45) (1971) 180–181 (in Russian). [12] V.P. Sazonov, About the equilibrium of three liquid in ternary systems. IV. System nitromethane + caprylic acid + water, Russ. J. Phys. Chem. 2 (45) (1971) 473–474 (in Russian). [13] He Xiuqiong, Huang Kun, Yu Pinhua, Zhang Chao, Xie Keng, Li Pengfei, Wang Juan, An Zhentaoand, Liu Huizhou, Liquid–liquid three phase extraction apparatus: operation strategy and influences on mass transfer efficiency, Chin. J. Chem. Eng. 20 (1) (2012) 27–35. [14] L. Liu, Y.S. Dong, Z.L. Xiu, Three-liquid-phase extraction of diosgenin and steroidal saponins from fermentation of Dioscorea zingibernsis C. H. Wright, Process Biochem. 45 (2010) 752–756. [15] J. Chen, H.Z. Liu, B. Wang, Study on the three-phase extraction of penicillin G with a single step method, Proceedings of the Conference on Solvent Extraction (ISEC2002), Cape Town, 2012, pp. 602–606. [16] L. Zhu, C.B. Tay, H.K. Lee, Liquid–liquid microextraction of aromatic amines from water samples combined with high-performance liquid chromatography, J. Chromatogr. A 963 (1–2) (2002) 231–237. [17] C. Basheer, A.A. Alnedhary, et al., Ionic liquid supported three-phase liquid– liquid microextraction as a sample preparation technique for aliphatic and aromatic hydrocarbons prior to gas chromatography–mass spectrometry, J. Chromatogr. A 1210 (1) (2008) 19–24.
[18] L. Boyadgiev, Three-phase liquid extraction–liquid membrance. Overview, Theor. Found. Chem. Technol. 6 (18) (1984) 735–743 (in Russian). [19] S. Carda-Broch, A. Berthod, D.W. Armstrong, Solvent properties of the 1-butyl3-methylimidazolium hexafluorophosphate ionic liquid, Anal. Bioanal. Chem. 375 (2003) 191–199. [20] V.T. Garov, L.A. Serafimov, Physical-chemical basis of distillation and rectification processes, Leningrad (1975) (in Russian). [21] A.K. Frokova, The separation of azeotropic mixtures, Physical–Chemical Basis and Technological Methods, Monograph. VLADOS Publ., 2010 p. 192 (in Russian). [22] O.N. Temkin, L.G. Bruk, K.Y. Odintsov, E.A. Katsman, I.V. Petrov, O.Y. Istomina, Kinetics of cyclohexene oxidation by p-quinones in aqueous-organic solutions of cationic palladium(II) complexes, Kinet. Katal. 5 (51) (2010) 691–703. [23] J. Acosta, A. Arce, E. Rodil, A. Soto, A thermodynamic study on binary and ternary mixtures of acetonitrile, water and butyl acetate, Fluid Phase Equilib. 203 (2002) 83–98. [24] F.D. Maslan, E.A. Stoddard, Acetonitrile + water liquid–vapor equilibrium, J. Phys. Chem. 60 (1956) 1146–1147. [25] A.-L. Vierk, Experimental investigation of the two-component systems: wateracetonitrile, water-dioxane, ethanol-acetonitrile and cyclohexane-dioxane, Z. Anorg. Chem. 261 (1950) 283. [26] D.F. Othmer, S. Josefoeitz, Composition of vapours from boiling binary solutions acetonitrile—water system, Ind. Eng. Chem. 39 (1947) 1175–1177. [27] N. Van Nhu, F.F. Kohler, Excess properties of mixtures of polar components and hydrocarbons of varying polarisability, Fluid Phase Equilib. 50 (1989) 267–296. [28] B. Wang, X. Ge, H. Zheng, T. Qiu, Y. Wu, Liquid–liquid equilibrium for the system water + cyclohexene + cyclohexanol over the temperature range of (303.2 to 403.2) K, J. Chem. Eng. Data 55 (7) (2010) 2529–2531. [29] J.W. McBain, K.J. Lissant, The solubilization of four typical hydrocarbons in aqueous solution by three typical detergents, J. Phys. Colloid Chem. 65 (1951) 655–662. [30] M. Frenkel, R.D. Chirico, V. Diky, A.F. Kazakov, C.D. Muzny, J.W. Magee, I. Abdulagatov, K. Kroenlein, J.W. Kang, NIST ThermoData Engine, NIST Standard Reference Database 103b-Pure Compounds, Binary Mixtures, and Chemical Reactions, Version 5.0; Standard Reference Data Program, National Institute of Standards and Technology, Gaithersburg, MD, 2010. [31] A. Fredenslund, R.L. Jones, J.M. Prausnitz, Group-contribution estimation of activity coefficients in nonideal liquid mixtures, AIChE J. 21 (1975) 1086. [32] T. Magnussen, P. Rasmussen, A. Fredenslund, UNIFAC parameter table for prediction constants of liquid liquid equilibria, Ind. Eng. Chem. Process Des. Dev. 20 (1980) 331–339. [33] P. Hansen, A. Fredenslund, M. Schiller, J. Gmehling, Vapor–liquid–equilibria by UNIFAC group contribution. 5. Revision and extension, Ind. Eng. Chem. Res. 30 (10) (1991) 2352–2355.
Contents lists available at ScienceDirect
Fluid Phase Equilibria j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / fl u i d
Liquid–liquid and liquid–liquid equilibrium for ternary system water– acetonitrile–cyclohexene at 298.15 K Anastasia Frolkova* , Darya Zakharova, Alla Frolkova, Stanislav Balbenov Department of Chemistry and Technology of Basic Organic Synthesis, Lomonosov Moscow State University of Fine Chemical Technology, Vernadskogo prospect 86, Moscow 119571, Russia
A R T I C L E I N F O
A B S T R A C T
Article history: Received 18 February 2015 Received in revised form 16 June 2015 Accepted 25 June 2015 Available online 2 July 2015
Liquid–liquid (LLE) and liquid–liquid equilibrium (LLLE) data for the ternary system water–acetonitrile– cyclohexene were obtained at 298.15 K and 99.06 kPa. The results of mathematical modelling of LLE and LLLE with the use of the NRTL and UNIFAC models were compared. Both models provide a good description of vapour–liquid equilibrium (VLE). It was determined that the experimental and calculated (NRTL) data are in good agreement, and it was demonstrated that the UNIFAC model could not be used for studying LLE and LLLE in the considered system. ã 2015 Elsevier B.V. All rights reserved.
Keywords: Liquid–liquid equilibrium Liquid–liquid equilibrium Azeotropic systems
1. Introduction The investigation of phase equilibrium in multicomponent multiphase systems is a complex task. One of the most effective methods of studying these is through mathematical modelling. There are several research studies devoted to development of algorithms for LLE and LLLE calculation, correlation and prediction [1–3]. The authors agree on the use of the NRTL model for the description of the phase equilibrium of multiphase systems. The parameters of the NRTL model should give both correct qualitative reproduction of the thermodynamic behaviour of the system and quantitative agreement with experimental data. However, experimental LLLE data are scarce compared with the VLE and LLE data. An analysis of the literature revealed approximately 60 experimentally-studied ternary systems. Currently, the systems most investigated are those containing water [4–12]. At the same time, the research of splitting systems is highly promising from the point of view of separation processes. Recently, the number of works devoted to development of three-liquidphase extraction for the separation of complex mixtures has increased [13–19]. The use of the splitting effect is analogous to separation processes based on distillation methods [20,21] because it is spontaneous and does not require additional energy
* Corresponding author. E-mail address: [email protected] (A. Frolkova). http://dx.doi.org/10.1016/j.fluid.2015.06.039 0378-3812/ ã 2015 Elsevier B.V. All rights reserved.
costs. Thus, the investigation of the liquid–liquid envelope is necessary for the design of separation processes. In the present study, the water–acetonitrile–cyclohexene system, which is an industrially important system for the synthesis of cyclohexanone [22]), was chosen as the object of a splittingdiagram study. There are number of experimental studies that present VLE and LLE data for the binary constituents of a ternary system. The binary systems water–acetonitrile and water–cyclohexene contain azeotropes with minimum boiling temperatures [23–27]. The water–acetonitrile system is homogeneous, and the other two are heterogeneous [28–29]. An analysis of the published data indicates that there are no experimental data for the liquid–liquid and liquid–liquid equilibrium in the considered ternary system. This work presents the results of our experimental study of LLE and LLLE in the water– acetonitrile–cyclohexene system at 298.15 K and 99.06 kPa. 2. Experimental 2.1. Materials The purities of the chemicals (see Table 1) were verified chromatographically and in terms of refraction indexes. All physicochemical constants of the pure substances were determined to be in agreement with the data in the literature [30]. The cyclohexene was purified by distillation and chromatographic analysis indicated that its purity practically did not change. The water was double-distilled.
A. Frolkova et al. / Fluid Phase Equilibria 408 (2016) 10–14 Table 1 The purities of the chemicals.
Table 3 Experimental (liquid + liquid) data for the system water–acetonitrile–cyclohexene for mole fractions (x) at temperature T = 298.15 K and pressure p = 99.06 kPa.a
Substance
Purity, mass fraction
Manufacturer
Water Acetonitrile Cyclohexene
0.999 0.999 0.990
– LAB-SCAN analytical sciences ACROS ORGANICS
Composition of coexisting phases, mole fraction
Table 2 Experimental (liquid + liquid + liquid) data for the system water–acetonitrile– cyclohexene for mole fractions (x) at temperature T = 298.15 K and pressure p = 99.06 kPa.a Composition of coexisting phases, mole fraction Phase 1
11
Phase 2
Phase 3
Water
Acetonitrile
Water
Acetonitrile
Water
Acetonitrile
0.894
0.103
0.321
0.620
0.009
0.116
Standard uncertainties are u(T) = 0.3 K, u(x) = 0.0032, and u(p) = 0.4 kPa.
2.2. Methods The LLE and LLLE were investigated using gas chromatography. Ternary mixtures of known composition within the splitting region were prepared by the gravimetric method using a ScienTech SA210 analytical balance with an accuracy of 0.0001 g. It was considered that the phase equilibrium is reached when there was a full distribution of phases among themselves. After phase equilibrium was reached the phases were separated using a
Phase 1
Phase 2
Water
Acetonitrile
Water
Acetonitrile
0.968 0.931 0.851 0.013 0.017
0.031 0.068 0.148 0.135 0.136
0.013 0.004 0.338 0.017 0.151
0.096 0.099 0.602 0.720 0.728
Standard uncertainties are u(T) = 0.3 K, u(x) = 0.0032, and u(p) = 0.4 kPa
separatory funnel and were analysed by gas chromatography. A LChM-80 chromatograph (Russia) was used with two packed columns, a Porapak Q (3 m) and a Porapak P (1 m), both with a 3 mm i.d. The column and injector temperatures were 453 K, and the detector temperature was 473 K. Notably good peak separation was achieved under these conditions. A method of internal normalization and relative calibration was used to calculate the compositions of the equilibrium liquid phases. Acetonitrile was used as the linking component. The uncertainty in the mole fraction was usually less than 0.003. At least three analyses were made of each liquid composition. 2.3. Results and discussion Experimental data on LLLE and LLE in system water– acetonitrile–cyclohexene are listed in Tables 2 and 3. A three-
Fig. 1. Splitting diagram of the water–acetonitrile–cyclohexene ternary system.
12
A. Frolkova et al. / Fluid Phase Equilibria 408 (2016) 10–14
Table 4 The NRTL binary interaction parameters for system water (1)—acetonitrile (2)— cyclohexene (3).
Aij Aji Bij(K) Bji(K) Cij
12
13
23
0.0 0.0 665.1194 183.5932 0.2858
8.2209 -2.9573 -27.1069 2317.7234 0.2
0.0 0.0 360.4846 555.6110 0.3
liquid-phase triangle and the binodal curves constructed on the basis of experimental data are presented in Fig. 1. The splitting
diagram contains one three-phase region, two two-phase splitting regions of the open type and one of the closed type. The next step was the mathematic modelling of the LLE and LLLE with the use of the correlating NRTL model and the predicting UNIFAC model. The binary interaction parameters for NRTL model are given in Table 4: X 0 1 X xi t ji Gji xm t mj Gmj X xj Gij B C j Bt ij mX C X ð1Þ þ lng i ¼ X @ A xk Gki x G x G k kj k kj j k
k
k
Table 5 Results of comparing the experimental data from the literature and the calculated azeotropic data (composition and boiling point) for the ternary system water–acetonitrile– cyclohexene at 101.30 kPa. Azeotrope
Literature data
Calculated data UNIFAC
Water– acetonitrile Water–cyclohexene Acetonitrile– cyclohexene Water–acetonitrile– cyclohexene
NRTL
Concentration of the first (second) component, mole fraction
G,K
0.319 0.309 –
349.35 0.329 343.95 0.319 – 0.495
348.48 0.324 343.93 0.319 338.16 0.489
349.94 343.90 338.73
–
–
333.96 0.195 (0348)
334.52
Concentration of the first (second) component, mole fraction
0.198 (0359)
G, K
Concentration of the first (second) component, mole fraction
Fig. 2. Distillation diagram of the water–acetonitrile–cyclohexene ternary system at 101.30 kPa.
G, K
A. Frolkova et al. / Fluid Phase Equilibria 408 (2016) 10–14
13
Table 6 Calculated data values of the LLLE of ternary system water–acetonitrile–cyclohexene at 298.15 K. Composition of coexisting phases, mole fraction Phase 1
Calculated (UNIFAC) RMSD = 7.67 % Calculated (NRTL) RMSD = 3.69 %
Phase 2
Phase 3
Water
Acetonitrile
Water
Acetonitrile
Water
Acetonitrile
0.881
0.117
0.155
0.700
0.02
0.118
0.882
0.117
0.259
0.672
0.004
0.095
Table 7 The calculated data values of the LLE of the water–acetonitrile–cyclohexene ternary system at 298.15 K. Composition of coexisting phases, mole fraction Calculated (UNIFAC)
Calculated (NRTL)
Phase 1
Phase 2
Phase 1
Phase 2
Water
Acetonitrile
Water
Acetonitrile
Water
Acetonitrile
Water
Acetonitrile
0.956 0.863 0.006 0.928 0.022 RMSD = 3.55%
0.043 0.136 0.151 0.071 0.124
0.016 0.210 0.023 0.018 0.161
0.041 0.722 0.737 0.069 0.691
0.957 0.848 0.0013 0.928 0.004 RMSD = 1.69%
0.042 0.147 0.133 0.071 0.102
0.003 0.340 0.025 0.003 0.173
0.040 0.608 0.765 0.068 0.725
where Gij = exp (aijt il);
t ij ¼ aij þ
liquid and liquid–liquid equilibria of the considered system. Moreover, the UNIFAC model gives a splitting region in the binary constituent water–acetonitrile, although it is well-known [24–25] that this system is homogeneous.
bij þ eij lnT þ f ij T; T
aij = cij+dij(T 273.15); and t ii = 0; Gii = 1; .
3. Conclusions
The approach to the UNIFAC method was developed in [31]: lng ¼ lng ci þ lng ri ;
ð2Þ
i i Z i i þ 1 ln þ 1 ; lng ¼ ln i i 2 ui ui where
S
Fi ¼ xi ri =
P
ng
xj rj ui ¼ xi z=2qi Sxj z=2qj ri Sk vki Rk qi ¼
ng k vki Q k :
The modelling was based on the UNIFAC parameters presented in [32,33]. A UNIFAC model simulation generally leads to results that are in good agreement with experimental data. Both models give a good description of the vapour–liquid equilibrium in the considered ternary system. The results of comparing the experimental data from the literature and the calculated azeotropic data (composition and boiling point) are presented in Table 5. The diagram of distillation lines is presented in Fig. 2. The diagram contains three binary and one ternary azeotrope with three distillation regions. The root-mean-square deviation (RMSD) of the phase composition was also calculated: M
RMSD ¼ 100
r n1 ðxexp ijk
S S S
k¼1 j¼1 i¼1
xcalc Þ2 ijk
rðn 1Þ
Experimental data for the LLE and LLLE were obtained for the water–acetonitrile–cyclohexene ternary system at 298.15 K and 99.06 kPa. The comparison of the experimental data with the values calculated on the basis of the NRTL model indicated that the parameters presented can be employed for studying the phase equilibrium of the considered system and for development of a flow-sheet for its separation. At the same time, we cannot recommend using the UNIFAC model for this purpose. Our research indicates that only experimentally confirmed parameters of a chosen model can be used for studying the phase equilibrium of the system. Acknowledgments This work was carried out according to the stated task of the Russian Ministry of Education and Science #10.99.2014/K. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.fluid.2015.06.039.
!1=2 ;
where xexp and xcalc are the experimental and calculated molar ijk ijk fraction component i in phase j on tie-line k; and M is the number of tie-lines. The calculated values (at 298.15 K) and the RMSD are presented in Tables 6 and 7. The simulation on the basis of NRTL model leads to results that are in good agreement with experimental data. However, the UNIFAC model cannot be recommended for studying the liquid–
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