VaporâLiquid Equilibrium for Mixtures of Ethylethylenediamine

Article pubs.acs.org/jced

Vapor−Liquid Equilibrium for Mixtures of Ethylethylenediamine, Ethylenediamine, and Water Åsa U. Burman and Krister H. U. Ström* Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Göteborg, Sweden S Supporting Information *

ABSTRACT: The temperature and the composition of the vapor and liquid phases at equilibrium were measured at atmospheric pressure and (50 and 20) kPa for the binary mixtures: water (1) and ethylenediamine (2, EDA); water and ethylethylenediamine (3, EtEDA); and EDA and EtEDA. For the ternary mixture of water, EDA, and EtEDA, equilibrium conditions were measured at atmospheric pressure. The vapor pressure of EtEDA was measured in the temperature range from (358 to 402) K, and Antoine parameters were fitted to the data. Parameters for the universal quasichemical (UNIQUAC) equation are estimated from binary data and applied to the ternary mixture. It was shown that the mixture of EDA and EtEDA has a zeotropic pinch close to pure EDA. Furthermore, it was found that the ternary mixture has a saddle point azeotrope at a molar fraction of 0.24 of water, 0.62 of EDA, and 0.14 of EtEDA and a temperature of 392.6 K at atmospheric pressure. Thus, the volatility between EDA and EtEDA is reversed in the water-rich region, and EtEDA is the most volatile component close to the binary azeotrope between water and EDA. This is illustrated by univolatility lines in a ternary diagram.

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INTRODUCTION Ethylenediamine (EDA, CAS Registry No. 107-15-3) is an intermediate in the production of chemicals such as bleach activators, fungicides, and chelating agents. It is a bifunctional solvent with two amine groups that can be involved in hydrogen bonding. EDA is hygroscopic. Ethylethylenediamine (EtEDA, CAS Registry No. 110-72-5) is a byproduct in the production of EDA. The mixture of EDA and water has a negative (maximum boiling) azeotrope reported at a molar fraction of water of 0.40 to 0.481−4 at 101.3 kPa. Negative azeotropes are not very common; less than 10 % of the known azeotropes are negative.5 According to Hirata et al.,3 the mixture is not azeotropic at pressures higher than 179 kPa. It has been found that EDA and EtEDA are difficult to separate from each other through distillation in the EDA-rich region.6,7 As very pure EDA is needed for many applications, the removal of EtEDA is a problem in the production of EDA. The vapor pressure for EtEDA has been measured by Cui et al.6 from (313 to 473) K. Vapor−liquid equilibrium (VLE) data for the binary mixture of water and EDA has been measured by Wilson1 at 101.3 kPa; Rivenq2 at (101.3, 80, 53.3, 26.7, and 13.3) kPa; Hirata et al.3 at (654.6, 559.3, 464.1, 272.6, 179.3, and 101.3) kPa; and by Schmelzer and Quitzsch4 at (101.3, 53.3, and 13.3) kPa. Cui et al.6 measured VLE for EDA and EtEDA at 101.3 kPa. However, no published data for the binary mixture of water and EtEDA have been found in the literature, nor any data for the ternary mixture of water, EDA, and EtEDA. In the work presented here, the vapor pressure of EtEDA was measured in the range of (358 to 402) K. VLE data were measured for atmospheric pressure and (50 and 20) kPa for the binary mixture of water and EDA as well as for EDA and EtEDA and for water and EtEDA. VLE was measured for the © XXXX American Chemical Society

ternary mixture of water, EDA, and EtEDA at atmospheric pressure. UNIQUAC parameters were estimated for the binary mixtures. All available data were included in the estimation for water and EDA and for EDA and EtEDA. The model with the estimated binary parameters was applied on bubble-point calculations for the ternary mixture.

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THEORY Parameters were estimated for the UNIQUAC equation:8 GE = RT

⎛ Φi ⎞ z ⎟+ 2 ⎝ xi ⎠

N

∑ xi ln⎜ i=1 N

−

N

⎛ Θi ⎞ ⎟ ⎝ Φi ⎠

∑ qixi ln⎜ i=1

N

∑ qixi ln(∑ Θjτji) i=1

(1)

j=1

where: Φi =

rx i i N ∑k = 1 rkxk

Θi =

qixi N ∑k = 1 qk xk

τij = e−aij + bijT / RT

In eq 1, GE/(J·mol−1) is the Gibbs excess energy, R/ (J·mol−1·K−1) is the gas constant, T/K is the temperature, xi is the molar fraction of component i in the liquid phase, N is the number of components, and z is the coordination number, set to 10, and aij/(J·mol−1) and bij/(J·mol−1·K−1) are binary interaction parameters. The pure component structural Received: July 23, 2012 Accepted: December 17, 2012

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dx.doi.org/10.1021/je300819g | J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

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Table 2. Measured Pressure P, Temperature T, and Mole Fraction in Liquid (x1) and Vapor (y1) at Equilibrium for Water (1) and EDA (2)a

parameters ri and qi are found in Table 1. For EtEDA the values are calculated from the equation given by Fredenslund et al.9 Table 1. Pure Component Parameters for the UNIQUAC Equation compound

ri

qi

ref

water ethylenediamine ethylethylenediamine

0.92 2.7384 4.1517

1.4 2.472 3.56

10 10 this study

For the other components they were obtained from the DECHEMA series.10 The gas phase was assumed to be ideal. The binary interaction parameters were estimated by minimizing the objective function: Np

Ψ=

∑ (GnE,exp − GnE,calc)2 n=1

(2)

where the experimental Gibbs excess energy is: ⎛ ⎛ P expy exp ⎞ ⎛ P expy exp ⎞⎞ GE,exp = RT ⎜⎜x1exp ln⎜ exp 1 o ⎟ + x 2exp ln⎜ exp 2 o ⎟⎟⎟ ⎝ x1 P1 ⎠ ⎝ x 2 P2 ⎠⎠ ⎝

(3)

exp

In eq 3 P /Pa is the experimentally measured total pressure, Pi°/Pa is the vapor pressure of component i, and yi is the molar fraction of component i in the gas phase. For the binary mixtures of water and EDA and EDA and EtEDA, data from literature were available as mentioned in the introduction. Those data were included in the estimation of the parameters. Equal weight was given to all the experimental points except for the outliers marked in Tables 2 to 4. The criterion used for deciding outliers were that the point deviated more than 20 % in GE from a curve through all of the points for each pressure series. The outliers were not included in the estimation of the parameters, but they are included in all other calculations and plots presented here. Residuals in the objective function for all data sets are plotted in the Supporting Information file. The vapor pressure of EDA and water was calculated with the Wagner equation: ⎛ Po ⎞ Aτ + Bτ1.5 + Cτ 3 + Dτ 6 ln⎜ i ⎟ = Tr ⎝ Pc ⎠

(4)

where τ = 1 − Tr; Tr = T/Tc, Tc/K and Pc/Pa are the critical temperature and pressure for the pure component. Parameters A, B, C, and D, Tc, and Pc were obtained from Reid et al.10 For the vapor pressure of EtEDA, the Antoine equation was applied: log10(Pio) = a −

b (T + c )

(5)

In eq 5 Pio is in kPa. Parameters a, b, and c were obtained from measurements made in this study of the vapor pressure of EtEDA (Table 5) and from extrapolation to pure EtEDA of end point measurements from this study. The squared difference of the calculated and experimental vapor pressure was minimized.

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P/kPa

T/K

x1

y1

101.8 101.8 101.7 100.2 101.7 101.7 100.1 101.8 101.9 100.0 101.7 99.9 101.7 101.6 100.0 101.6 100.1 100.2 101.7 99.8b 101.8 99.8b 100.0 101.9 101.9 99.9 101.9 100.1 100.0 101.9 49.9 49.7 49.8 49.8 49.8 49.9 49.8 49.8 49.8 49.8 49.8 49.8 49.8 19.8 19.8 19.8 19.8 19.8 19.8 19.8 19.8 19.8 19.8

390.8 390.8 389.9 389.5 390.6 391.2 391.0 391.7 391.8 391.3 391.2 390.1 389.5 387.7 387.0 385.1 384.6 384.8 382.7 383.3b 380.2 379.8b 376.8 377.2 375.5 373.9 373.9 373.3 372.7 373.2 369.3 371.2 372.5 372.9 371.7 368.9 367.1 364.9 361.1 358.2 355.9 354.8 354.3 346.7 348.6 350.2 351.6 351.2 347.6 341.4 336.9 334.4 333.6

0.001 0.001 0.028 0.041 0.115 0.219 0.285 0.320 0.445 0.465 0.555 0.593 0.648 0.706 0.717 0.757 0.761 0.778 0.801 0.803b 0.841 0.852b 0.888 0.891 0.929 0.945 0.966 0.973 1.000 1.000 0.027 0.267 0.389 0.514 0.616 0.715 0.760 0.797 0.846 0.890 0.946 0.976 1.000 0.005 0.166 0.327 0.506 0.612 0.721 0.817 0.904 0.969 1.000

0.001 0.001 0.030 0.042 0.085 0.195 0.258 0.287 0.457 0.479 0.621 0.682 0.767 0.861 0.863 0.919 0.919 0.936 0.957 0.969b 0.980 0.984b 0.994 0.993 0.997 0.998 1.000 0.999 1.000 1.000 0.023 0.165 0.344 0.527 0.711 0.857 0.927 0.961 0.979 0.996 0.999 1.000 1.000 0.000 0.050 0.210 0.463 0.686 0.889 0.985 0.997 1.000 1.000

a u(T) = 0.1 K, u(P) = 0.6 kPa, u(x1) = u(y1) = 0.005. bOutliers not included in the parameter estimation.

METHODS Information about the chemicals used for making samples is found in Table 6. As internal standard for the gas chromatography, 3-ethylamino-1-propylamine (CAS 104-78-

9) from ACROS with stated purity >0.99 in molar fraction was used. B



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Table 3. Measured Pressure P, Temperature T, and Mole Fraction in Liquid (x1) and Vapor (y1) at Equilibrium for Water (1) and EtEDA (2)a

Table 4. Measured Pressure P, Temperature T, and Mole Fraction in Liquid (x1) and Vapor (y1) at Equilibrium for EDA (1) and EtEDA (2)a

P/kPa

T/K

x1

y1

P/kPa

T/K

x1

y1

101.2 101.2b 101.1 101.9 101.2 101.2 101.3 101.3 101.3 101.4b 101.4 101.4 49.8 49.8 49.8 49.8 49.8 49.8 49.8 49.8 49.8 49.8 49.8 49.8 49.8 19.8 19.8 19.8 19.8 19.8 19.8 19.8 19.8 19.8 19.8 19.8 19.8 19.8

401.9 392.2b 386.4 382.7 380.9 378.5 376.8 375.3 374.2 373.3b 373.3 373.1 380.2 380.0 372.6 368.3 365.3 362.9 360.5 358.7 356.8 356.0 355.2 354.6 354.3 355.8 355.6 351.0 347.8 344.2 342.3 340.5 337.8 336.2 335.1 334.1 333.7 333.5

0.000 0.226b 0.460 0.645 0.707 0.803 0.858 0.900 0.941 0.968b 0.987 1.000 0.015 0.078 0.285 0.475 0.634 0.731 0.790 0.842 0.905 0.934 0.964 0.989 1.000 0.027 0.077 0.267 0.482 0.632 0.724 0.792 0.857 0.901 0.934 0.968 0.989 1.000

0.001 0.448b 0.695 0.832 0.874 0.920 0.958 0.978 0.990 0.994b 0.997 1.000 0.029 0.124 0.441 0.667 0.796 0.891 0.938 0.967 0.985 0.991 0.996 0.999 1.000 0.042 0.106 0.402 0.655 0.808 0.907 0.947 0.974 0.989 0.995 0.997 0.999 1.000

101.2 101.2 101.3 101.3 101.5b 101.6 101.7 101.7 101.7 101.7 101.7 101.7 101.7 101.7 101.8b 101.8 49.8b 49.8 49.8 49.8 49.8 49.8 49.8 49.8 49.8 49.8 49.8 49.9 19.8b 19.8 19.8 19.8 19.8 19.8 19.8 19.8 19.8 19.8 19.8 19.8b

402.2 400.6 398.6 397.5 396.4b 393.0 392.0 391.4 391.1 390.7 390.5 390.2 390.1 390.1 390.0b 390.8 380.2b 378.7 376.5 374.2 372.9 371.6 370.8 370.4 369.9 369.7 369.3 369.3 355.8b 354.7 353.2 351.3 349.7 348.5 347.8 347.3 346.9 346.7 346.3 346.7b

0.002 0.045 0.138 0.204 0.326b 0.522 0.644 0.718 0.770 0.830 0.873 0.908 0.946 0.972 0.993b 0.999 0.003b 0.048 0.145 0.275 0.434 0.537 0.676 0.754 0.833 0.903 0.979 0.994 0.002b 0.053 0.130 0.280 0.425 0.545 0.662 0.754 0.829 0.905 0.983 0.999b

0.002 0.098 0.243 0.327 0.472b 0.652 0.740 0.793 0.824 0.867 0.896 0.929 0.960 0.977 0.996b 0.999 0.004b 0.090 0.258 0.398 0.549 0.668 0.753 0.807 0.869 0.920 0.981 0.995 0.005b 0.099 0.237 0.399 0.549 0.661 0.757 0.807 0.861 0.931 0.986 1.000b

a u(T) = 0.1 K, u(P) = 0.6 kPa, u(x1) = u(y1) = 0.005. bOutliers not included in the parameter estimation. a

u(T) = 0.1 K, u(P) = 0.6 kPa, u(x1) = u(y1) = 0.005. bOutliers not included in the parameter estimation.

The VLE measurements were performed on a Fisher Labodest equipment, model 602, with recirculation of both vapor and liquid phases. The recirculated phases were mixed before reentering the cell which was equipped with an electrical immersion heater and a Cottrell pump. On heating the liquid to boiling, the evolved vapor rose through the Cottrell pump and continuously carried with it slugs of liquid. The temperature was measured using a Pt100 thermo element. Calibrations were performed with Quartz thermometer 2804A using the ITS-90 temperature scale, and the estimated accuracy of the temperature measurements was ± 0.1 K. The pressure was measured by two Fischer digital manometers calibrated through vapor pressure measurements for bidistilled water. By comparing measurements for pure water, the standard deviation for the pressure measurements was estimated to 0.6 kPa. Comparisons between the measured vapor pressure of water and the expression found in Poling et al.10 are found in the Supporting

Table 5. Experimental Vapor Pressure, Po, for Ethylethylenediamine at Temperature Ta T/K

P°/kPa

PCuib/kPa

358.0 366.5 374.1 380.3 390.2 398.3 402.2

20.8 29.6 39.5 49.7 69.5 90.2 101.5

40.5 48.9 57.5 65.4 79.7 92.7 99.6

a

u(T) = 0.1 K, u(P) = 0.6 kPa. bAs a comparison, vapor pressures at the same temperatures calculated with the equation by Cui et al.,6 PCui.

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Table 6. Information about the Chemicals chemical name water ethylenediamine ethylethylenediamine

source Akzo Nobel Fluka

initial purity mass fraction

purification method

analysis method

0.998 0.996

bidistilled used as received used as received

gas chromatography gas chromatography

final measurement as the EtEDA was discolored at an attempt to increase the pressure above atmospheric pressure. Most likely EtEDA is hygroscopic, and it is possible that it has absorbed water from the air during the measurement. However, as the apparatus was not open to the air other than for loading of the apparatus and for the final measurement at atmospheric pressure, this problem ought not be very important. The experimental data is presented in Tables 2 to 4 for the binary systems and in Table 7 for the ternary one. The UNIQUAC parameters estimated from data from this study and data from literature, where available, are found in Table 8. The residuals in calculated bubble-point temperature for the binary water and EDA and vapor composition for the data sets included in parameter estimations are shown in Figures 1 and 2. The absolute average deviation (AAD) is defined as the arithmetic mean of the absolute value of the difference between the calculated value and the experimental value. For all water and EDA data, the total AAD between calculated and experimental bubble-point temperatures was 0.48 K, and the total AAD in molar fraction for the vapor phase was 0.013. Residual plots for the two other binaries are available in the Supporting Information. For water and EtEDA, the AAD in bubble-point temperature was 0.42 K, and the AAD in vapor phase composition 0.008. For EDA and EtEDA, the AAD in bubble point temperature was 0.27 K, and the AAD in vapor phase composition was 0.012. The five data points given at atmospheric pressure for EDA and EtEDA in Cui et al.6 agree well with the data in this study. The binary UNIQUAC parameters were used in bubblepoint calculations for the ternary mixture. Resulting residuals are available in the Supporting Information. The results compare well with the results for the binary mixtures: the AAD in calculated and experimental temperature was 0.57 K, and the AAD in molar fraction for the vapor phase was 0.025 for water, 0.011 for EDA, and 0.016 for EtEDA. The largest errors are found in the water-rich area and for the composition of water. One plausible explanation for this is the well-known difficulty with water in GC composition determinations, but it can also be an inability of the UNIQUAC equation to model the strong intermolecular interactions in the mixture. The temperature residuals are not scattered around zero. This most likely indicates that more accurate vapor pressure data are needed. For the binary water and EDA, a maximum boiling azeotrope is found for each of the three pressures investigated. Figure 3 shows log10P vs 1/T with the conditions for the azeotropic points inserted for data from the literature and from this study. As can be seen, a straight line can be drawn through all the points. This line intersects the line of the vapor pressure for EDA at 151 kPa and 403 K, indicating that the azeotrope can be broken at pressures above.13 Hirata et al.3 found no azeotrope at 179 kPa, but the bubble and dew points are very close to each other. This very low relative volatility from pure EDA to a molar fraction of water of 0.4 still makes separation by distillation unsuitable at this pressure. As the azeotrope is maximum boiling, the deviation from Raoult's law is negative.

Information. The charge volume was approximately 100 mL. The heating was set such that 1 to 2 drops of condensed vapor phase per second were obtained. The equilibrium cell was operated under constant pressure conditions and the cell was then left for at least 20 min until equilibrium conditions were reached. Samples [(1 to 2) mL] of liquid phase and condensed vapor phase were taken for analysis. For the measurements of EDA and water, each pressure series was measured separately. Both pure components were used as starting point for preparing the VLE mixtures, and the other pure component was added in steps. For the binary mixtures with EtEDA the (50 and 20) kPa series were coordinated and the measurement series started from pure EtEDA. The measurements for the ternary mixtures were performed at atmospheric pressure with pure EtEDA as the starting point. Pure EDA and water was then added in steps. Analysis. The composition of the phases was determined by gas chromatography (GC). The column was nonpolar with cross bound methylsiloxane. The carrier gas was hydrogen, and a flame ionization detector was used. The split ratio was 17:1. From an internal standard (3-ethylamino-1-propylamine and ethanol (12 g·L−1)), 10 mL was added to each sample. Eleven standards were made out of mixtures of EDA and EtEDA. When the amount of the amines had been determined, the water content was calculated as the rest of the sample. Three analyses were made for each sample. The maximum deviation between quadruple tests was 0.005 molar fraction units. Test points of mixtures between the standard mixture compositions deviated at most 0.007 molar fraction units. Some samples were checked with Karl Fischer titration, but as the samples reacted with moisture in the air, the precision of the Karl Fischer titration was lower than that obtained with GC.

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RESULTS AND DISCUSSION The vapor pressure measured for EtEDA is presented in Table 5. This data and extrapolated data from end point measurements in the binary series were used to estimate Antoine parameters for eq 5: a = 6.07713, b = 1253.9, and c = −94.138 for Pio in kPa and T in K. The residuals between calculated and experimental pressure are presented in the Supporting Information. The difference between the measured vapor pressure for EtEDA from this study and from Cui et al.6 is considerable: at temperatures below the normal boiling point, the values from Cui et al.6 are as high as 20 kPa above the values from this study. Around the normal boiling point the values agree. Vapor pressures calculated with the equation given by Cui et al.6 are shown in a column in Table 5 for comparison. When the measurements are compared with predictions from the Thodos-Gomez method for polar compounds,11 the same pattern is observed: the vapor pressure data from Cui et al.6 are too high for temperatures below the normal boiling point, and they quickly become much lower than those from the prediction method above the normal boiling point. The vapor pressure predictions agree well with the measurements for EDA from Hieber and Woerner12 and for EtEDA from this study. The purity of EtEDA in this study was not checked after the D



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Table 7. Measured Pressure P, Temperature T, and Mole Fraction in Liquid (xi) and Vapor (yi) at Equilibrium for Water (1), EDA (2), and EtEDA (3)a

a

P/kPa

T/K

x1

x2

y1

y2

102.1 102.1 102.1 102.1 102.1 102.1 102.1 102.1 102.1 102.1 101.3 101.3 101.2 101.2 101.2 101.2 101.2 101.1 101.1 101.1 101.1 101.1 101.1 101.2 101.2 101.2 101.2 101.3 101.3 101.3 101.3 101.3 101.4 101.3 101.3 101.3 101.3 101.0 101.1 101.2 101.2 101.2 101.3

403.0 399.7 393.8 393.9 394.5 389.7 387.9 386.0 385.6 386.3 387.0 387.7 386.5 385.5 384.0 382.8 381.6 383.0 384.4 386.1 387.2 388.2 388.7 389.6 388.8 388.0 386.6 385.5 384.3 382.6 381.6 383.4 384.7 386.2 387.5 388.4 389.3 389.9 390.5 388.9 386.1 382.7 380.8

0.000 0.059 0.143 0.226 0.136 0.341 0.475 0.516 0.591 0.531 0.539 0.517 0.570 0.626 0.685 0.727 0.756 0.732 0.702 0.656 0.622 0.588 0.561 0.531 0.587 0.631 0.676 0.722 0.748 0.779 0.803 0.766 0.739 0.672 0.646 0.606 0.594 0.590 0.568 0.626 0.724 0.804 0.823

0.002 0.017 0.017 0.050 0.123 0.094 0.076 0.071 0.096 0.146 0.173 0.215 0.192 0.169 0.144 0.125 0.112 0.140 0.175 0.230 0.268 0.311 0.342 0.379 0.336 0.301 0.265 0.229 0.208 0.183 0.164 0.202 0.230 0.296 0.323 0.365 0.381 0.388 0.413 0.358 0.263 0.187 0.170

0.000 0.249 0.417 0.341 0.293 0.521 0.643 0.708 0.740 0.702 0.673 0.623 0.700 0.757 0.821 0.864 0.894 0.867 0.835 0.770 0.728 0.675 0.627 0.579 0.634 0.631 0.798 0.848 0.885 0.922 0.945 0.916 0.882 0.848 0.795 0.742 0.722 0.680 0.625 0.718 0.868 0.956 0.964

0.001 0.027 0.020 0.064 0.147 0.085 0.054 0.040 0.049 0.079 0.105 0.149 0.108 0.081 0.052 0.036 0.026 0.041 0.062 0.113 0.150 0.201 0.248 0.299 0.246 0.217 0.128 0.093 0.068 0.044 0.030 0.053 0.082 0.113 0.162 0.213 0.238 0.282 0.340 0.254 0.116 0.036 0.030

Figure 1. Residuals for vapor-phase composition of water (1) versus liquid phase composition of water for calculations with the UNIQUAC model for the binary water (1)−EDA (2) system. Experimental data from: ×, Wilson1 (smoothed); △, Schmelzer and Quitzsch;4 ◇, Hirata et al.3 (smoothed for 1 atm); +, Rivenq;2 and *, this study.

Figure 2. Residuals for bubble-point temperature of water (1) versus liquid phase composition of water for calculations with the UNIQUAC model for the binary water (1)−EDA (2) system. Experimental data from: ×, Wilson1 (smoothed); △, Schmelzer and Quitzsch;4 ◇, Hirata et al.3 (smoothed for 1 atm); +, Rivenq;2 and *, this study.

Figure 3. Location of the azeotrope for water and ethylenediamine. The dotted line is the vapor pressure for pure EDA, and the solid line passes through observed values for the azeotrope. Experimental data from: ×, Wilson1 (smoothed); △, Schmelzer and Quitzsch;4 ◇, Hirata et al.3 (smoothed for 1 atm); +, Rivenq2 and ○, this study.

u(T) = 0.1 K, u(P) = 0.6 kPa, u(x1) = u(y1) = u(x2) = u(y2) = 0.005.

In the data by Rivenq2 it is clear that the activity coefficient, γ1, for water passes through a minimum in the range with low water content for pressures smaller than or equal to 53.3 kPa. Wilson1 presents smoothed data at 1 atm with a minimum. The

Table 8. UNIQUAC Parameters Estimated in This Study aij and bij/J·mol−1·K−1 a12

a21

b12

b21

binary

J·mol−1

J·mol−1

J·mol−1·K−1

J·mol−1·K−1

water−ethylenediamine water−ethylethylenediamine ethylenediamine−ethylethylenediamine

−2356.72 5852.09 −2383.53

−2685.32 −4248.97 4429.07

35.4224 −5.6231 17.178

−11.1533 6.76 −34.0308

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Hirata et al.3 smoothed data at 1 atm do not have a minimum. At higher pressures by Hirata et al., the scatter in experimental data makes it difficult to determine whether there is a minimum or not. The data presented in this study for atmospheric pressure and for 50 kPa support the idea that there is a minimum, but there are only four experimental points in the concentration range of interest (Figure 4). Schmelzer and

Figure 5. Isoterms for the ternary mixture of water, ethylenediamine, and ethylethylenediamine at atmospheric pressure (101.3 kPa). The saddle point is located between the 391.65 K isotherms and marked by *.

Figure 4. Activity coefficient vs molar fraction of water (1) in a mixture with EDA (lower set) and EtEDA (upper set). Experimental data: *, 50 kPa, this study in EDA mixture; +, 53.3 kPa, Rivenq2 in EDA mixture; and ▲, 50 kPa, this study in EtEDA mixture. Lines calculated from the UNIQUAC equation for 50 kPa: solid line for mixture with EDA and dotted line for mixture with EtEDA.

and the unidistribution lines are plotted in Figure 6. The relative volatility is defined as:

Quitzsch4 do not have any data in the concentration range where the minimum appears, nor does the measurement series at 20 kPa presented in this study. If the activity coefficient versus the composition passes through a minimum neither the van Laar-type nor the Wilson equation is applicable.14 However, the minimum is not reproduced by the UNIQUAC equation with the parameters presented in Table 8 either (see Figure 4). The binary water and EtEDA do not form an azeotrope at the pressures investigated in this study. The boiling points of the pure components at atmospheric pressure are 100 °C for water and 129 °C for EtEDA. Azeotropes for compounds with such a considerable difference in boiling temperature are rare5 as they would require extreme deviation from Raoult's law to cause the tangent of the total pressure curve to be horizontal. The deviation from Raoult's law for water and EtEDA is negative, as it was for water and EDA as well. There are too little data to see if there is a minimum in the activity coefficient, but the two first data points in the (50 and 20) kPa series respectively indicate that it is possible (see Figure 4). Many industrial applications require extremely pure EDA and the removal of EtEDA by distillation has been found to be very difficult.7 It can be seen from the data in Table 4 that EDA and EtEDA is tangentially zeotropic, with a tangential pinch in the range of high concentration of EDA (see Figure s12 in the Supporting Information). EDA and EtEDA has a positive deviation from Raoult's law. The isotherms for the ternary mixture at atmospheric pressure are plotted using the binary UNIQUAC models in Figure 5. A ternary azeotrope, saddle point, is predicted at a molar fraction of 0.24 of water, 0.62 of EDA, and 0.14 of EtEDA and a temperature of 392.6 K. This is a min−max azeotrope: it is a maximum in the boiling point parallel to the axis from pure water to pure EDA and at the same time a minimum along a line perpendicular to that axis. The univolatility lines, along which the relative volatility is one,

Figure 6. Univolatility lines (αij = 1), unidistribution lines (Ki = 1), and regions of K-ranking for the ternary mixture of water (1), ethylendiamine (2), and ethylethylenediamine (3) calculated with the binary UNIQUAC models at 101.3 kPa. The boundaries for the regions of K-ranking are the univolatility lines. Experimental data points for the ternary marked by ×.

αij =

y /xi Ki = i Kj yj /xj

where Ki is the distribution coefficient of component i, yi the molar fraction of component i in the vapor, and xi the molar fraction of component i in the liquid. The univolatility line for water and EDA starts on the axis between pure EDA and pure water at the binary azeotrope. The three univolatility lines intersect at the ternary azeotrope. The univolatility lines divide the composition triangle into regions of K-ranking. These regions are shown in Figure 6 with the most volatile component first and the heaviest last. Note that EtEDA is the most volatile component close to the binary azeotrope F



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ACKNOWLEDGMENTS The authors are indebted to AKZO-Nobel Stenungsund for supplying ethylenediamine, ethylethylenediamine, and expertize in gas chromatography and to Jana Stepanova for skillful assistance in the experimental work.

between EDA and water. One plausible physical explanation is that the bulky ethyl group in EtEDA disturbs the hydrogen bonding structure in the ternary mixture to a considerable extent. The unidistribution line along which K3 = 1 is also shown in Figure 6. To the right of this line, K3 > 1, and thus the vapor is enriched in EtEDA. Note that the order of volatility between EDA and EtEDA is reversed above the α23 univolatility line. This explains how Do et al.7 could obtain the EtEDA in a water rich top fraction of a distillation column, avoiding the difficult separation between EDA and EtEDA in the EDA-rich region. The experimental data points for the ternary mixture are marked by x in Figure 6. The regions of K-ranking through which they pass are confirmed experimentally. However, some experimental points are almost on the α13 line, and there the calculated and experimental results disagree for some of the points.

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REFERENCES

(1) Wilson, A. L. New Aliphatic Amines. Ind. Eng. Chem. 1935, 27, 867−871. (2) Rivenq, F. Ebulliometri des mélanges eau-éthylènediamine. Bull. Soc. Chim. Fr. 1963, 8−9, 1606−1608. (3) Hirata, M. S.; Hakuta, S.; Nagahama, T. K. Vapor-liquid equilibria under elevated pressurespressure effect on the azeotropic mixture of ethylene diamine−water. J. Chem. Eng. Jpn. 1969, 2, 143−149. (4) Schmelzer, J.; Quitzsch, K. Isobare Flüssigkeit-Dampfgleichgewichte der binären Systeme Benzol-Ä thylendiamin und WasserÄ thylendiamin. Z. Phys. Chem. (Leipzig) 1973, 252, 280−288. (5) Hilmen, E.-K. Separation of Azeotropic Mixtures: Tools for Analysis and Studies on Batch Distillation Operation. Dr. Eng. dissertation, Norwegian University of Science and Technology, 2000. (6) Cui, X.; Huang, Y.; Guo, Y.; Yang, Z. Solvent selection for extractive distillation of Ethylenediamine-N-Ethylethylenediamine. Shihua Jishu 2007, 36, 165−168. (7) Do, D.; Domke, C. H.; Lopez-Toledo, J.; Petraitis, D. M.; Srnak, T. Z. Methods for making ethanolamines and ethyleneamines from ethylene oxide and ammonia, and related methods. U.S. patent application 2010/0087684 A1. Apr 8, 2010. (8) Reid, R. C.; Prausnitz, J. M.; Poling, B. E. The Properties of Gases and Liquids, 4th ed.; McGraw-Hill: New York, 1987. (9) Fredenslund, A. A.; Gmehling, J.; Rasmussen, P. Vapor-liquid equilibria using UNIFAC: a group contribution method; Elsevier Science Ltd.: Amsterdam, 1977. (10) Ghmeling, J.; Onken, U.; Artl, W. Vapour-liquid Equilibrium Data Collection; DECHEMA chemistry data series: Frankfurt, 1977− 1997. (11) Gomez-Nieto, M.; Thodos, G. Generalized treatment for the vapor pressure behavior of polar and hydrogen-bonding compounds. Can. J. Chem. Eng. 1977, 55, 445−449. (12) Hieber, W.; Woerner, A. Thermodynamische messungen an komplexbildenden aminen und alkoholen. Z. Electrochem. 1934, 40, 252−256. (13) Nutting, H. S.; Horsley, L. H. Graphical Method for Predicting Effect of Pressure on Azeotropic Systems. Anal. Chem. 1947, 19, 602− 603. (14) Prausnitz, J. M.; Lichtenthaler, R. N.; Gomes de Azevedo, E. Molecular Thermodynamics of fluid−phase equilibria, 2nd ed.; PrenticeHall: Upper Saddle River, NJ, 1986.

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CONCLUSION The vapor pressure of EDA and VLE data for the binary and ternary systems with water, EDA, and EtEDA were measured in a constant-pressure equilibrium still. The liquid and vapor phase compositions were determined by gas chromatography. The data measured in this study and literature data, when available, were used to estimate temperature-dependent binary UNIQUAC parameters. Antoine parameters were estimated for EtEDA. The measurements from this study agree well with prediction methods, but below atmospheric pressure they do not agree with the data by Cui et al.6 The binary system water− EtEDA does not have an azeotrope at the pressures investigated. Both water−EDA and water−EtEDA have a negative deviation from Raoult's law. The binary system EDA− EtEDA has a tangential pinch close to pure EDA. Bubble-point calculations with the binary parameters for the ternary mixture were compared with data measured at 1 atm. The accuracy was found to be similar to that for the binary systems. According to the UNIQUAC model there is a ternary azeotrope, a saddle point, at a molar fraction of EDA of 0.62, of water of 0.24 and of EtEDA of 0.14. The existence three univolatility lines have been experimentally verified: α12 by binary data and α13 and α23 by ternary data. In an area close to the binary azeotrope between EDA and water, EtEDA is the most volatile component. By separating off EtEDA in mixtures of those compositions, the difficult separation in the region close to pure EDA can be avoided.

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Article

ASSOCIATED CONTENT

* Supporting Information S

Graphs of the objective function from the estimation of binary UNIQUAC parameters (s1−s3). Residuals in vapor pressure of pure water (s4), EtEDA (s5), and in bubble-point temperature and vapor composition for water and EtEDA (s6−s7); EDA and EtEDA (s8−s9); and for the ternary (s10−s11). Plot of dew and bubble points for EDA and EtEDA (s12). This material is available free of charge via the Internet at http:// pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*Telephone: +46 31 772 5708. Fax: +46 31 772 3035. E-mail: [email protected]. Notes

The authors declare no competing financial interest. G


VaporâLiquid Equilibrium for Mixtures of Ethylethylenediamine

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