Ind. Eng. Chem. Res. 2001, 40, 5831-5838
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GENERAL RESEARCH Vapor-Liquid Equilibria and Enthalpies of Mixing in a Temperature Range from 298.15 to 413.15 K for the Further Development of Modified UNIFAC (Dortmund) Roland Wittig,† Ju 1 rgen Lohmann,‡ Ralph Joh,§ Sven Horstmann,| and Ju 1 rgen Gmehling*,† Lehrstuhl fu¨ r Technische Chemie (FB9), Carl von Ossietzky Universita¨ t Oldenburg,⊥ Postfach 2503, D-26111 Oldenburg, Germany, BASF Coatings AG, Werk Mu¨ nster, Postfach 6123, D-48163 Mu¨ nster, Germany, Siemens Axiva GmbH & Co. KG, Industriepark Ho¨ chst, D-65926 Frankfurt/Main, Germany, and Laboratory for Thermophysical Properties (LTP GmbH), Universita¨ t Oldenburg, Postfach 2503, D-26111 Oldenburg, Germany
Isothermal P-x data (VLE) and excess enthalpy (hE) data for the binary systems methyl formate, ethyl formate, and butyl formate + water and toluene + 1,2-ethanediol have been measured with the help of a computer-operated static apparatus and an isothermal flow calorimeter. Additionally, hE data for the binary systems benzene + 1,2-ethanediol and benzene and ethanol + N,N-dimethylacetamide have been determined. The experimental VLE and hE data have been used for the revision and extension of the group contribution method Modified UNIFAC (Dortmund). Besides these new data various types of thermodynamic data (vapor-liquid equilibria (VLE), excess enthalpies (hE), activity coefficients at infinite dilution (γ∞), liquidliquid equilibria (LLE), solid-liquid equilibria (SLE), and azeotropic data (AZD)) taken from the Dortmund Data Bank have simultaneously been used for fitting temperature-dependent group interaction parameters. The new or revised Modified UNIFAC (Dortmund) parameter pairs for the new main group “dialkylated amides” and the interaction between formates and water are given. The predicted results are in good agreement with the experimental data. Introduction For the description of the phase equilibrium behavior, gE models can be used. These models allow the prediction of multicomponent systems from binary data. If no experimental data are available, group contribution methods such as Modified UNIFAC (Dortmund)1,2 can be employed. For the revision and extension of this method systematic measurements are carried out in our laboratory. In this paper isothermal P-x data for the binary systems methyl formate, ethyl formate, and butyl formate + water at 298.15 K and toluene + 1,2-ethanediol at 323.15 K are given. They were measured with the help of a computer-operated static apparatus.3,4 VLE data provide the information about the composition dependence of the activity coefficients. Therefore, these data are the basic data for fitting group interaction parameters for Modified UNIFAC (Dortmund). Additionally, hE data for the binary systems ethyl * To whom correspondence should be addressed. E-mail:
[email protected]. † Lehrstuhl fu ¨ r Technische Chemie (FB9), Carl von Ossietzky Universita¨t Oldenburg. ‡ BASF Coatings AG. § Siemens Axiva GmbH & Co. KG. | LTP GmbH, Universita ¨ t Oldenburg. ⊥ http://www.uni-oldenburg.de/tchemie.
formate and butyl formate + water at 363.15 K, methyl formate + water at 323.15 K, benzene and toluene + 1,2-ethanediol at 363.15 and 413.15 K, and benzene and ethanol + N,N-dimethylacetamide at 363.15 K are given. They were measured with the help of an isothermal flow calorimeter.5,6 hE data provide the most important information about the temperature dependence of the activity coefficient, which is described quantitatively by the Gibbs-Helmholtz equation:
( ) ∂ ln γi ∂(1/T)
P,x
)
h h Ei R
(1)
Using this equation, a direct relationship between the temperature dependence of the activity coefficient (γi) and the partial molar excess enthalpy (h h Ei ) is given. hE data sets at high temperatures up to 413.15 K are most important as supporting data for fitting temperaturedependent group interaction parameters for Modified UNIFAC (Dortmund).7 Most of the published hE data were determined around room temperature.5 Therefore, in our laboratory in particular systematic measurements at high temperatures are carried out. The experimental VLE and hE data of this work together with various types of thermodynamic data (γ∞, LLE, SLE, and AZD) taken fom the Dortmund Data Bank (DDB)8 have been used for fitting temperature-
10.1021/ie010444j CCC: $20.00 © 2001 American Chemical Society Published on Web 11/01/2001
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Table 1. Suppliers, Purities, Water Contents, and CAS Numbers of the Chemicals Used
compound
supplier
ethanol 1,2-ethanediol benzene toluene methyl formate ethyl formate n-butyl formate N,N-dimethylacetamide
Baker Scharlau Scharlau Scharlau Aldrich Aldrich Aldrich Aldrich
water purity content (% GC) (mass ppm) 99.99 99.99 99.99 99.97 99.99 99.97 99.27 99.80
70 40 30 70 80 40 50 50
CAS number [64-17-5] [107-21-1] [71-43-2] [108-88-3] [107-31-3] [109-94-4] [592-84-7] [127-19-5]
Table 2. Experimental P-x Data for the System Methyl Formate (1) + Water (2) at 298.15 K x1
P (kPa)
x1
P (kPa)
x1
P (kPa)
0.0000 0.0024 0.0069 0.0115 0.0158 0.0222 0.0292 0.0529 0.0687 0.0797
3.36 6.71 12.50 18.22 23.55 30.97 38.41 58.58 67.77 72.41
0.0917 0.1182 0.1486 0.1506 0.1842 0.2140 0.2578 0.3100 0.4421 0.5908
74.23 74.24 74.24 74.26 74.24 74.25 74.22 74.24 74.23 74.21
0.6620 0.7329 0.7901 0.8438 0.8798 0.9120 0.9396 0.9624 0.9829 1.0000
74.20 74.20 74.36 74.67 75.39 76.05 76.97 77.70 78.31 78.45
Table 3. Experimental hE Data for the System Methyl Formate (1) + Water (2) 323.15 K and 1.755 MPa x1
hE (J‚mol-1)
x1
hE (J‚mol-1)
x1
hE (J‚mol-1)
0.0152 0.0315 0.0491 0.0682 0.0889 0.1115 0.1362
1 21 58 113 180 257 302
0.1779 0.2445 0.3279 0.4676 0.5394 0.6239 0.6721
360 454 578 804 922 1065 1099
0.7249 0.7831 0.8476 0.9195 0.9586
1074 995 836 530 320
Table 5. Experimental hE Data for the System Ethyl Formate (1) + Water (2) 363.15 K and 1.686 MPa x1
hE (J‚mol-1)
x1
hE (J‚mol-1)
x1
hE (J‚mol-1)
0.0117 0.0244 0.0382 0.0532 0.0697 0.0879
61 137 191 221 254 291
0.1080 0.1425 0.1990 0.6115 0.6692 0.7349
332 404 519 1396 1514 1651
0.7713 0.8103 0.8523 0.8976 0.9467
1595 1460 1235 924 539
Table 6. Experimental P-x Data for the System Butyl Formate (1) + Water (2) at 298.15 K x1
P (kPa)
x1
P (kPa)
x1
P (kPa)
0.0000 0.0002 0.0004 0.0006 0.0008 0.0009 0.0013 0.0017 0.0021 0.0027 0.0039 0.0065 0.0101 0.0146 0.0201 0.0264 0.0335 0.0414
3.30 3.94 4.58 5.19 5.76 6.42 6.80 6.80 6.80 6.80 6.79 6.79 6.79 6.79 6.79 6.79 6.79 6.79
0.0504 0.0602 0.0711 0.0817 0.0928 0.1049 0.1160 0.1280 0.1407 0.1562 0.1744 0.1950 0.2182 0.2453 0.2801 0.3200 0.3677 0.4211
6.80 6.80 6.80 6.80 6.81 6.81 6.82 6.81 6.81 6.80 6.80 6.79 6.79 6.79 6.78 6.78 6.78 6.77
0.4831 0.5539 0.6324 0.7157 0.7981 0.8701 0.9121 0.9309 0.9439 0.9573 0.9707 0.9795 0.9839 0.9884 0.9930 1.0000
6.77 6.77 6.77 6.77 6.77 6.76 6.75 6.74 6.65 6.43 5.74 5.44 5.13 4.78 4.43 3.84
Table 7. Experimental hE Data for the System Water (1) + Butyl Formate (2) 363.15 K and 1.755 MPa x1
Table 4. Experimental P-x Data for the System Ethyl Formate (1) + Water (2) at 298.15 K x1
P (kPa)
x1
P (kPa)
x1
P (kPa)
0.0000 0.0026 0.0057 0.0080 0.0111 0.0158 0.0221 0.0307 0.0415 0.0553 0.0722 0.0939
3.31 7.41 12.14 15.58 19.87 25.96 33.46 33.77 33.76 33.76 33.76 33.75
0.1179 0.1771 0.1946 0.2598 0.2704 0.3741 0.5082 0.6449 0.7029 0.7592 0.8033 0.8280
33.75 33.73 33.69 33.72 33.67 33.66 33.64 33.62 33.61 33.60 33.59 33.59
0.8498 0.8670 0.8855 0.9049 0.9223 0.9361 0.9528 0.9660 0.9911 1.0000
33.58 33.58 33.57 33.56 33.54 33.48 33.33 33.16 32.83 32.71
dependent group interaction parameters for Modified UNIFAC (Dortmund) simultaneously. The group interaction parameters for the new group “dialkylated amides” with aromatic compounds and alcohols and between formates and water are given. The parameters for aromatic compounds and 1,2-ethanediol have already been published elsewhere. Typical results for formates, glycol, and N,N-dimethylacetamide using Modified UNIFAC (Dortmund) are presented. The systems in this paper were chosen for the systematic further development of Modified UNIFAC (Dortmund). All mentioned compounds have a wide range of application and are of great industrial interest. Most of the methyl formate is converted on a large scale into formic acid and formamide. Ethyl formate is used for the synthesis of vitamin B1 and as a flavor in
0.0741 0.1395 0.1976 0.2496 0.2965 0.3389
hE
(J‚mol-1) 882 1334 1240 1152 1077 1014
x1
hE (J‚mol-1)
x1
hE (J‚mol-1)
0.4126 0.4745 0.8512 0.8953 0.9215 0.9365
907 812 238 173 133 109
0.9499 0.9620 0.9728 0.9827 0.9917
88 71 55 41 28
Table 8. Experimental hE Data for the System Benzene (1) + 1,2-Ethanediol (2) 363.15 K and 1.652 MPa x1
hE (J‚mol-1)
x1
hE (J‚mol-1)
x1
hE (J‚mol-1)
0.0157 0.0317 0.0647 0.0990 0.1347 0.1719 0.2107
94 191 353 393 403 404 405
0.2511 0.2934 0.3375 0.3838 0.4322 0.4830 0.5363
405 406 407 409 407 407 407
0.5924 0.6514 0.7136 0.7792 0.8486 0.9221 0.9605
408 408 411 411 411 413 413
x1
hE (J‚mol-1)
x1
hE (J‚mol-1)
x1
hE (J‚mol-1)
0.0157 0.0317 0.0647 0.0990 0.1347 0.1719 0.2106
138 280 557 823 972 991 1006
0.2511 0.2933 0.3375 0.4322 0.4829 0.5363 0.5923
1022 1035 1050 1085 1107 1129 1151
0.6513 0.7135 0.7792 0.8486 0.9221 0.9604
1178 1200 1231 1256 1288 815
413.15 K and 1.376 MPa
the food industry. It is also used as a solvent for acetyl cellulose and nitrocellulose.9 1,2-Ethanediol is mainly used as an antifreeze in automobile radiators and as a raw material for the manufacture of polyester fibers.9 1,2-Ethanediol is also
Ind. Eng. Chem. Res., Vol. 40, No. 24, 2001 5833 Table 9. Experimental P-x Data for the System Toluene (1) + 1,2-Ethanediol (2) at 323.15 K x1
P (kPa)
x1
P (kPa)
x1
P (kPa)
0.0000 0.0011 0.0018 0.0024 0.0030 0.0035 0.0041 0.0047 0.0052 0.0057 0.0067 0.0086 0.0111 0.0142 0.0194 0.0378 0.0514 0.0646 0.0799 0.0983 0.1216
0.26 0.89 1.30 1.64 2.00 2.32 2.62 2.94 3.22 3.49 4.00 4.99 6.15 7.52 9.51 12.33 12.44 12.47 12.49 12.50 12.49
0.1437 0.1648 0.1896 0.2130 0.2350 0.2559 0.2756 0.2782 0.2979 0.3008 0.3273 0.3591 0.3923 0.4261 0.4590 0.4933 0.5308 0.5716 0.6129 0.6570 0.7037
12.49 12.50 12.50 12.50 12.50 12.50 12.51 12.50 12.51 12.48 12.46 12.45 12.44 12.44 12.44 12.43 12.43 12.43 12.43 12.43 12.43
0.7479 0.7928 0.8373 0.8741 0.9006 0.9248 0.9465 0.9611 0.9717 0.9757 0.9797 0.9837 0.9878 0.9899 0.9919 0.9939 0.9960 0.9980 1.0000
12.43 12.43 12.42 12.42 12.42 12.43 12.43 12.42 12.42 12.42 12.42 12.41 12.40 12.39 12.37 12.33 12.31 12.28 12.25
Table 10. Experimental hE Data for the System Toluene (1) + 1,2-Ethanediol (2) 363.15 K and 1.617 MPa x1
hE (J‚mol-1)
x1
hE (J‚mol-1)
x1
hE (J‚mol-1)
0.0132 0.0267 0.0547 0.0842 0.1153 0.1480 0.1825
97 193 242 256 261 264 269
0.2191 0.2578 0.2989 0.3891 0.4387 0.4918 0.5487
272 276 279 288 293 299 305
0.6099 0.6758 0.7470 0.8242 0.9083 0.9531
311 319 327 335 345 349
x1
hE (J‚mol-1)
x1
hE (J‚mol-1)
x1
hE (J‚mol-1)
0.0132 0.0267 0.0547 0.0842 0.1153 0.1480 0.1825
143 291 575 651 672 691 711
0.2191 0.2578 0.2989 0.3426 0.3891 0.4387 0.4918
733 758 783 814 837 866 902
0.5487 0.6099 0.6758 0.7470 0.8242 0.9083 0.9531
936 976 1020 1062 1101 1160 1186
413.15 K and 1.617 MPa
Table 12. Experimental hE Data for the System Ethanol (1) + N,N-Dimethylacetamide (2) 363.15 K and 1.893 MPa x1
hE (J‚mol-1)
x1
hE (J‚mol-1)
x1
hE (J‚mol-1)
0.0767 0.1492 0.2178 0.2829 0.3447 0.4035 0.4594
-75 -136 -185 -220 -244 -254 -255
0.5127 0.5636 0.6121 0.6586 0.7030 0.7456 0.7864
-247 -235 -219 -200 -181 -162 -139
0.8256 0.8633 0.8994 0.9342 0.9677
-116 -93 -72 -51 -29
hE measurements the compounds were used after purification without degassing. The resulting purity as determined by gas chromatography together with the water content obtained by Karl-Fischer titration are listed in Table 1. The measurements of the P-x data were performed with a computer-driven static apparatus.3,4 The total pressure P is measured for different overall compositions at constant temperature T. The apparatus can be applied at temperatures between 278 and 368 K and pressures up to 0.3 MPa. The degassed, pure compounds are filled into the evacuated thermostated equilibrium cell using precise thermostated piston injectors. The pressure in the cell is monitored with a Digiquartz pressure sensor (Model 245A, Paroscientific) and the temperature is determined with a Pt100 resistance thermometer (Model 1506, Hart Scientific). The total composition can be derived from the known volumes of the liquids injected. Taking the vapor-liquid equilibrium into account, the liquid-phase compositions are obtained from the total compositions by solving the mass and volume balance. The uncertainties of this device are as follows: σ(T) ) 0.03 K, σ(P) ) 20 Pa ( 0.0001 (P/ Pa), and σ(xi) ) 0.0001. The hE data were determined with the help of an isothermal flow calorimeter (Model 7501, Hart Scientific).5,6 The calorimeter consists of two solvent pumps
Table 11. Experimental hE Data for the System Benzene (1) + N,N-Dimethylacetamide (2) 363.15 K and 1.955 MPa x1
hE (J‚mol-1)
x1
hE (J‚mol-1)
x1
hE (J‚mol-1)
0.0259 0.0517 0.1032 0.1546 0.2057 0.2567 0.3075
-12 -22 -43 -64 -82 -98 -109
0.3581 0.4085 0.4588 0.5089 0.5587 0.6085 0.6580
-115 -120 -123 -122 -117 -108 -97
0.7074 0.7566 0.8056 0.8545 0.9031 0.9517 0.9758
-86 -67 -45 -24 -7 2 2
an important solvent for extraction and extractive distillation. N,N-Dimethylacetamide is a very effective solvent used in separation technology. Furthermore, it is a very good polymer solvent, dissolving polyacrylates and polyesters.9 Experimental Section The chemicals were purchased from different commercial suppliers. For the VLE measurements the chemicals were dried over a molecular sieve, degassed, and distilled using a 1.5-m Vigreux column.10 For the
Figure 1. Experimental and predicted data of the system methyl formate (1) + water (2). (A) P-x data: this work at (b) 298.15 K. (B) hE data: this work at (b) 323.15 K. (C) Activity coefficients at infinite dilution of methyl formate in water: (O).21-23 (s) Modified UNIFAC (Dortmund).
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Figure 3. Experimental and predicted data of the system butyl formate (1) + water (2) (A) P-x data: this work at (b) 298.15 K; (B) hE data: this work at (b) 363.15 K; (C) LLE data: (O)29 and (4);30 (s) Modified UNIFAC (Dortmund).
Figure 2. Experimental and predicted data of the system ethyl formate (1) + water (2). (A) P-x(y) data: this work at (b) 298.15 K; (O)14 at 320 K. (B) hE data: this work at (b) 363.15 K. (C) LLE data: (O)24 and (4).25 (D) Activity coefficients at infinite dilution of ethyl formate in water: (O).21,22,26 (E) Azeotropic data: (O)27 and (4).28 (s) Modified UNIFAC (Dortmund).
(Model LC-2600, ISCO), a thermostated flow cell, and a back-pressure regulator to prevent evaporation. The device can be applied in a temperature range from 273 K up to 453 K. The pressure can be kept constant within pressures up to 14 MPa. The pumps provide a flow of constant composition through the flow cell. This cell is equipped with a pulsed heater and a Peltier cooler. The combination of cooler and heater allows not only the determination of endothermic effects but also exothermic effects. The uncertainties of this apparatus are as follows: σ(T) ) 0.03 K, σ(hE) ) 2 J‚mol-1 ( 0.01 (hE/J‚ mol-1), and σ(xi) ) 0.0001. Results Because in Modified UNIFAC (Dortmund) temperature-dependent parameters are used,
[
Ψnm ) exp -
]
anm + bnmT + cnmT2 T
(2)
this method allows a reliable temperature extrapolation of the activity coefficient when an adequate database covering the whole temperature range is used. For fitting group interaction parameters of Modified UNIFAC (Dortmund) up to seven different types of thermodynamic mixture data (VLE, γ∞, hE, excess heat capaci-
Figure 4. Experimental and predicted data of the system 1,2ethanediol (1) + naphthalene (2). (A) T-x-y data: (O)31 at 100 kPa; and of the system benzene (1) + 1,2-ethanediol (2) (B) hE data: this work at (b) 363.15 K and (2) 413.15 K; (C) LLE data: (O),32 (0);33 (D) activity coefficients at infinite dilution of benzene in 1,2-ethanediol: (O);34-48 (s) Modified UNIFAC (Dortmund).
ties (cEp ), LLE, SLE, and AZD) are used simultaneously. Most of the experimental data are taken from the Dortmund Data Bank (DDB).8 If the necessary data are not available, systematic measurements are carried out. Thermodynamic, inconsistent VLE data have to be excluded before starting with the fitting procedure. Furthermore, weighting factors are used for the various types of thermodynamic mixture data. Each type of mixture data fulfills its own job:
Ind. Eng. Chem. Res., Vol. 40, No. 24, 2001 5835
Figure 5. Experimental and predicted data of the system toluene (1) + 1,2-ethanediol (2). (A) P-x data: this work at (b) 323.15 K; (B) hE data: this work at (b) 363.15 K and (2) 413.15 K; (C) LLE data: (O)49 and (4);50 (D) activity coefficients at infinite dilution of toluene in 1,2-ethanediol: (O)34-42,51,52; (s) Modified UNIFAC (Dortmund).
(1) VLE data and AZD are the most important data. They provide the information about the composition dependence of the activity coefficients. (2) γ∞ data not only give information about the temperature dependence of the activity coefficients but also describe the real phase behavior in the dilute region. With the help of γ∞ data separation factors at infinite dilution can be obtained. Activity coefficients at infinite dilution are of great industrial interest because they can directly be used for the selection of selective solvents for the extractive distillation or extraction.11 (3) hE data provide the most important information about the temperature dependence of the activity coefficient. Therefore, hE data at high temperatures up to 413.15 K are used as supporting data for fitting temperature-dependent group interaction parameters.7 (4) cEp data provide the information about the temperature dependence of the excess enthalpies. (5) SLE data of eutectic systems are valuable supporting data at low temperatures (
