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Vapor–liquid equilibrium in the system ethane + ethylene glycol
Fluid Phase Equilibria 240 (2006) 220–223
Short communication
Vapor–liquid equilibrium in the system ethane + ethylene glycol Fang-Yuan Jou, Kurt A.G. Schmidt 1 , Alan E. Mather ∗ Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alta. T6G 2G6, Canada Received 5 September 2005; received in revised form 28 December 2005; accepted 30 December 2005
Abstract The solubility of ethane in ethylene glycol (EG) has been determined at temperatures in the range 298–398 K at pressures up to 20 MPa. The experimental results were correlated by the Peng–Robinson equation of state, and interaction parameters have been obtained for this system. The parameters in the Krichevsky–Ilinskaya equation were calculated from these interaction parameters. © 2006 Published by Elsevier B.V. Keywords: Solubility; Ethane; Ethylene glycol; Equation of state; Gas dehydration
1. Introduction Glycols are widely used in the natural gas industry to dehydrate gas streams and/or inhibit the formation of hydrates. The solubility of the light hydrocarbons in glycols is important, as the dissolved hydrocarbons constitute a loss to the process, and results in hydrocarbon emissions to the atmosphere. As such, the estimation of the hydrocarbon content in the glycol is imperative in the design and evaluation phase of these processes. Despite this importance, there are only a limited number of experimental data sets dealing with the solubility of the lighter hydrocarbons in glycols. This paper is a contribution in the continuing effort by this laboratory to measure the solubility of light hydrocarbons in glycols at the temperatures and pressures often experienced in these processes. Previously we have measured the solubility of methane in ethylene glycol (EG) [1] and the solubility of propane in ethylene glycol [2]. 2. Experimental The apparatus and experimental technique that were used are similar to those described by Jou et al. [3]. The equilibrium cell was mounted in an air bath. The temperature of the contents of the cell was measured by a calibrated iron-constantan ther∗
Corresponding author. Tel.: +1 780 492 3957; fax: +1 780 492 2881. E-mail address: [email protected] (A.E. Mather). 1 Present address: Department of Physics and Technology, University of Bergen, Allegat´en 55, N-5007 Bergen, Norway. 0378-3812/$ – see front matter © 2006 Published by Elsevier B.V. doi:10.1016/j.fluid.2005.12.032
mocouple and the pressure in the cell was measured by digital Heise gauges (0–10, 0–35 MPa). These gauges had an accuracy of ±0.1% of full scale by comparison with a dead-weight gauge. The thermocouple had an accuracy of ±0.1 ◦ C by comparison with a platinum resistance thermometer. The ethylene glycol (EG, CAS No. 107-21-1) was obtained from Aldrich and had a purity of 99%. Ethane was obtained from Matheson and had a purity of 99%. Prior to the introduction of the fluids, the cell was evacuated. About 120 cm3 of EG was drawn into the cell. It was heated to 110 ◦ C and a vacuum applied to remove traces of water. Chromatographic analysis indicated that the water content of the EG was 0.1 mol%. The ethane was added to the cell by the cylinder pressure or by means of a spindle press. The circulation pump was started and the vapor bubbled through the solvent for at least 8 h to ensure that equilibrium was reached. A sample of the liquid phase, 2–20 g, depending on the solubility, was withdrawn from the cell into a 50 cm3 sample bomb, which had previously been evacuated and weighed. The bomb contained a magnetic stirring bar to help in degassing the sample. The sample bomb was reweighed to determine the mass of the sample and then attached to a vacuum rack. The rack consisted of 6.35 mm o.d. stainless steel tubing connected to a calibrated Digigauge (0–1.0 MPa) and a 50 cm3 burette. The rack was evacuated and the gas allowed to evolve from the sample bomb into the burette. The moles collected were calculated from the P-V-T data, assuming ideal gas behavior. A correction was made for the residual ethane left in the sample at atmospheric pressure. The uncertainty in the liquid phase analyses is estimated to be ±3%.
F.-Y. Jou et al. / Fluid Phase Equilibria 240 (2006) 220–223
221
Table 1 Solubility of ethane (2) in ethylene glycol (1) 298.15 K
323.15 K × 103
P (MPa)
x2
0.0996 0.577 2.51 4.21a 5.53 9.50 15.17 20.34
0.583 3.12 11.7 16.4 16.8 17.7 19.2 20.3
a
348.15 K × 103
P (MPa)
x2
0.0972 0.816 2.69 6.40 10.34 15.11 19.50
0.458 3.43 10.2 18.0 19.4 20.5 22.1
373.15 K × 103
P (MPa)
x2
0.133 0.919 3.53 7.54 13.65 19.23
0.487 3.24 11.1 18.3 22.2 24.3
398.15 K × 103
P (MPa)
x2
0.100 0.784 2.54 6.58 10.94 14.81 18.25
0.334 2.59 7.97 17.1 22.5 25.8 28.0
P (MPa)
x2 × 103
0.135 0.666 5.60 9.27 13.95 18.25
0.407 2.14 14.9 21.4 28.8 30.8
Three-phase point (vapor, ethane-rich liquid, EG-rich liquid).
4. Discussion
Fig. 1. Experimental data for the EG (1) + ethane (2) system compared with correlated values using the Peng–Robinson equation.
The equilibrium data were correlated in the manner described by Jou et al. [3]. The method requires that an equation of state valid for the solvent and dilute solutions of the solute in the solvent be available. The Peng–Robinson [4] equation of state was used in the calculations. The parameters a22 and b2 of the ethane were obtained from the critical constants. The parameters a11 and b1 for EG were obtained from the vapor pressure and liquid density, as EG decomposes before reaching its critical temperature. The critical constants and acentric factors of the ethane and the equations for the vapor pressure and density of EG were taken from the compilation of Rowley et al. [5]. The resulting values of a11 and b1 for EG, and a22 and b2 for ethane are given in Table 2. The experimental solubility data were used to obtain the binary interaction parameter k12 which appears in the mixing rule of the equation of state: a12 = (a11 a22 )1/2 (1 − k12 )
3. Results The solubility of ethane in ethylene glycol was determined at the temperatures of 298.15, 323.15, 348.15, 373.15, and 398.15 K at pressures up to 20.3 MPa. The experimental data are presented in Table 1 and plotted in Fig. 1. At the lowest temperature, a sharp transition occurs between (vapor + liquid) and (liquid + liquid) equilibria. At higher pressures a liquid ethanerich phase is in equilibrium with the liquid glycol phase. At 298.15 K, there is a cusp at 4.21 MPa, which is the three-phase pressure where ethane-rich liquid, vapor and glycol-rich liquid coexist.
(1)
In two-phase regions, the isothermal flash routine algorithm presented by Whitson and Brul´e [6] was used. The binary interaction parameter was iteratively modified until the difference in the calculated and experimental liquid mole fractions was less than the set tolerance. Values of k12 were found to be dependent on the temperature and can be fitted by a linear relationship: k12 = 9.22 × 10−4 T (K) − 0.264
(2)
The correlation reproduces the experimental data with an overall average per cent deviation in the mole fraction of 2.1%, about the same as the experimental uncertainty.
Table 2 Equation of state parameters T (K)
298.15 323.15 348.15 373.15 398.15
Ethylene glycol (1)
k12
Ethane (2)
a11 (Pa m6 mol−2 )
b1 (cm3 mol−1 )
a22 (Pa m6 mol−2 )
b2 (cm3 mol−1 )
3.66 3.51 3.37 3.24 3.11
51.7 51.9 52.1 52.3 52.4
0.612 0.587 0.562 0.540 0.518
40.5 40.5 40.5 40.5 40.5
0.011 0.034 0.057 0.080 0.103
F.-Y. Jou et al. / Fluid Phase Equilibria 240 (2006) 220–223
222 Table 3 Calculated three-phase pressure and compositions
Table 4 Parameters of the Krichevsky–Ilinskaya equation
T (K) P (MPa) y1 × 106 x2␣ × 103  x1 × 103 P2s (MPa)
T (K)
H12 (MPa)
3 −1 v¯ ∞ 2 (cm mol )
A/RT
298.15 323.15 348.15 373.15 398.15
176.4 220.4 257.3 285.2 303.0
48.7 50.2 52.1 54.2 56.8
3.00 2.91 2.82 2.74 2.68
298.15 4.20 39 16 0.6 4.19
The binary interaction parameter, which was fit to the twophase data, and the pure component parameters were then used to predict a three-phase bubble point pressure. The three-phase bubble point calculation was performed with the three-phase bubble point technique described by Nutakki et al. [7] and Shinta and Firoozabadi [8]. Based on this technique and the abovementioned parameters, the calculated three-phase pressure and compositions are given in Table 3, together with the vapor pressure of pure ethane. The calculated mole fraction of ethane in the ethylene glycol phase is in good agreement with the experimental value given in Table 1. The vapor phase is essentially pure ethane and the calculated three-phase pressure is very close to the vapor pressure of pure ethane, and is lower than the experimental value. Gjaldbæk and Niemann [9] measured the solubility of ethane in ethylene glycol at atmospheric pressure (0.103 MPa) and 298.15 and 308.15 K. Using the pure component parameters in Table 2 and the binary interaction parameter, the liquid mole fraction was predicted. The overall predicted average absolute percentage deviation for both points was 5.3%, which is within the experimental uncertainty. Recently, Wang et al. [10] also performed experimental measurements for this system. Twenty data points were obtained at 283.2, 293.2 and 303.2 K at pressures up to 4.0 MPa. Unfortunately, there are no common temperatures to make a direct comparison. Again, using the pure component parameters in Table 2 and the binary interaction parameters from Eq. (2), the liquid mole fraction was predicted. The results are shown in Fig. 2 and it can be seen that there is a large difference between
Fig. 2. Experimental data of Wang et al. compared with calculated values using the Peng–Robinson equation.
the predicted values and the data of Wang et al., the overall predicted average absolute percentage deviation being 37.5%. The experimental procedure used by Wang et al. is similar to that employed in this work. However, they make no mention of correcting for the ethane dissolved in the glycol at atmospheric pressure. This could explain why their results are lower in mole fraction than the present work. Bender et al. [11] have shown the connection between the Peng–Robinson EOS, the binary interaction parameter and the three parameters in the Krichevsky–Ilinskaya equation. This equation is discussed in the book by Prausnitz et al. [12] and is given by: ∧ f2 v¯ ∞ (P − P1s ) A 2 ln = ln H21 + 2 (3) + (x − 1) x2 RT RT 1 The three parameters are the Henry’s constant, H21 , the partial molar volume at infinite dilution, and the Margules parameter, A. Recently, Schmidt [13] has corrected the equations which relate these parameters to the binary interaction parameter in the Peng–Robinson equation of state. The equations were used to obtain the three parameters and they are given in Table 4. The Henry’s constant for ethane in ethylene glycol is plotted in Fig. 3 for comparison with those for methane and propane. Also shown is the point obtained for ethane in ethylene glycol by Lenoir et al. [14]. It is much lower than the values for ethane obtained in the present work. Hayduk [15], in a critical review of solubility data for ethane in a number of solvents, concluded that the data presented by Lenoir et al. [14] are unreliable.
Fig. 3. The temperature dependence of the Henry’s constants for light hydrocarbons in EG.
F.-Y. Jou et al. / Fluid Phase Equilibria 240 (2006) 220–223
List of symbols a parameter in the Peng–Robinson equation (Pa m6 /mol2 ) A Margules parameter (J/mol) b parameter in the Peng–Robinson equation (cm3 /mol) ˆfi fugacity of component i in a mixture (kPa) H21 Henry’s constant of solute 2 in solvent 1 at P1s (MPa) kij binary interaction parameter in the Peng–Robinson equation Pis vapor pressure of component i (MPa) P pressure (MPa) R gas constant (J/mol K) T absolute temperature (K) v¯ ∞ partial molar volume at infinite dilution (cm3 /mol) 2 xi mole fraction of component i in the liquid phase yi mole fraction of component i in the vapor phase Superscripts ␣ ethylene glycol-rich phase  ethane-rich phase Acknowledgement The authors are grateful to the Natural Sciences and Engineering Research Council of Canada for financial support of this research.
223
References [1] F.-Y. Jou, F.D. Otto, A.E. Mather, Can. J. Chem. Eng. 72 (1994) 130–133. [2] F.-Y. Jou, F.D. Otto, A.E. Mather, J. Chem. Thermo. 25 (1993) 37–40. [3] F.-Y. Jou, R.D. Deshmukh, F.D. Otto, A.E. Mather, Fluid Phase Equilbr. 36 (1987) 121–140. [4] D.-Y. Peng, D.B. Robinson, Ind. Eng. Chem. Fundam. 15 (1976) 59–64. [5] R.L. Rowley, W.V. Wilding, J.L. Oscarson, Y. Yang, N.A. Zundel, T.E. Daubert, R.P. Danner, DIPPR Data Compilation of Pure Compound Properties, Design Institute for Physical Properties, AIChE, New York, USA, 2003. [6] C.H. Whitson, M.R. Brul´e, Phase behaviour, SPE Monograph Series 20, Society of Petroleum Engineers: Richardson, Texas, USA, 2000. [7] R. Nutakki, A. Firoozabadi, T.W. Wong, K. Aziz, SPE 17390, SPE/DOE Enhanced Oil Recovery Symposium, Tulsa, OK, USA, April 17–20, 1988. [8] A.A. Shinta, A. Firoozabadi, SPE Reserv. Eng. 12 (1997) 131–137. [9] J.C. Gjaldbæk, H. Niemann, Acta Chem. Scand. 12 (1958) 1015–1023. [10] L.-K. Wang, G.-J. Chen, G.-H. Han, X.-Q. Guo, T.-M. Guo, Fluid Phase Equilbr. 207 (2003) 143–154. [11] E. Bender, U. Klein, W.P. Schmitt, J.M. Prausnitz, Fluid Phase Equilbr. 15 (1984) 241–255. [12] J.M. Prausnitz, R.N. Lichtenthaler, E.G. de Azevedo, Molecular Thermodynamics of Fluid-phase Equilibria, 3rd ed., Prentice-Hall, Englewood Cliffs, NJ, 1999, p. 592. [13] K.A.G. Schmidt, Fluid Phase Equilbr. 236 (2005) 268–269. [14] J.-Y. Lenoir, P. Renault, H. Renon, J. Chem. Eng. Data 16 (1971) 340–342. [15] Hayduk, W., Ethane. IUPAC Solubility Data Series 9, Pergamon Press, Oxford, England, UK, 1982, p. 167.
Short communication
Vapor–liquid equilibrium in the system ethane + ethylene glycol Fang-Yuan Jou, Kurt A.G. Schmidt 1 , Alan E. Mather ∗ Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alta. T6G 2G6, Canada Received 5 September 2005; received in revised form 28 December 2005; accepted 30 December 2005
Abstract The solubility of ethane in ethylene glycol (EG) has been determined at temperatures in the range 298–398 K at pressures up to 20 MPa. The experimental results were correlated by the Peng–Robinson equation of state, and interaction parameters have been obtained for this system. The parameters in the Krichevsky–Ilinskaya equation were calculated from these interaction parameters. © 2006 Published by Elsevier B.V. Keywords: Solubility; Ethane; Ethylene glycol; Equation of state; Gas dehydration
1. Introduction Glycols are widely used in the natural gas industry to dehydrate gas streams and/or inhibit the formation of hydrates. The solubility of the light hydrocarbons in glycols is important, as the dissolved hydrocarbons constitute a loss to the process, and results in hydrocarbon emissions to the atmosphere. As such, the estimation of the hydrocarbon content in the glycol is imperative in the design and evaluation phase of these processes. Despite this importance, there are only a limited number of experimental data sets dealing with the solubility of the lighter hydrocarbons in glycols. This paper is a contribution in the continuing effort by this laboratory to measure the solubility of light hydrocarbons in glycols at the temperatures and pressures often experienced in these processes. Previously we have measured the solubility of methane in ethylene glycol (EG) [1] and the solubility of propane in ethylene glycol [2]. 2. Experimental The apparatus and experimental technique that were used are similar to those described by Jou et al. [3]. The equilibrium cell was mounted in an air bath. The temperature of the contents of the cell was measured by a calibrated iron-constantan ther∗
Corresponding author. Tel.: +1 780 492 3957; fax: +1 780 492 2881. E-mail address: [email protected] (A.E. Mather). 1 Present address: Department of Physics and Technology, University of Bergen, Allegat´en 55, N-5007 Bergen, Norway. 0378-3812/$ – see front matter © 2006 Published by Elsevier B.V. doi:10.1016/j.fluid.2005.12.032
mocouple and the pressure in the cell was measured by digital Heise gauges (0–10, 0–35 MPa). These gauges had an accuracy of ±0.1% of full scale by comparison with a dead-weight gauge. The thermocouple had an accuracy of ±0.1 ◦ C by comparison with a platinum resistance thermometer. The ethylene glycol (EG, CAS No. 107-21-1) was obtained from Aldrich and had a purity of 99%. Ethane was obtained from Matheson and had a purity of 99%. Prior to the introduction of the fluids, the cell was evacuated. About 120 cm3 of EG was drawn into the cell. It was heated to 110 ◦ C and a vacuum applied to remove traces of water. Chromatographic analysis indicated that the water content of the EG was 0.1 mol%. The ethane was added to the cell by the cylinder pressure or by means of a spindle press. The circulation pump was started and the vapor bubbled through the solvent for at least 8 h to ensure that equilibrium was reached. A sample of the liquid phase, 2–20 g, depending on the solubility, was withdrawn from the cell into a 50 cm3 sample bomb, which had previously been evacuated and weighed. The bomb contained a magnetic stirring bar to help in degassing the sample. The sample bomb was reweighed to determine the mass of the sample and then attached to a vacuum rack. The rack consisted of 6.35 mm o.d. stainless steel tubing connected to a calibrated Digigauge (0–1.0 MPa) and a 50 cm3 burette. The rack was evacuated and the gas allowed to evolve from the sample bomb into the burette. The moles collected were calculated from the P-V-T data, assuming ideal gas behavior. A correction was made for the residual ethane left in the sample at atmospheric pressure. The uncertainty in the liquid phase analyses is estimated to be ±3%.
F.-Y. Jou et al. / Fluid Phase Equilibria 240 (2006) 220–223
221
Table 1 Solubility of ethane (2) in ethylene glycol (1) 298.15 K
323.15 K × 103
P (MPa)
x2
0.0996 0.577 2.51 4.21a 5.53 9.50 15.17 20.34
0.583 3.12 11.7 16.4 16.8 17.7 19.2 20.3
a
348.15 K × 103
P (MPa)
x2
0.0972 0.816 2.69 6.40 10.34 15.11 19.50
0.458 3.43 10.2 18.0 19.4 20.5 22.1
373.15 K × 103
P (MPa)
x2
0.133 0.919 3.53 7.54 13.65 19.23
0.487 3.24 11.1 18.3 22.2 24.3
398.15 K × 103
P (MPa)
x2
0.100 0.784 2.54 6.58 10.94 14.81 18.25
0.334 2.59 7.97 17.1 22.5 25.8 28.0
P (MPa)
x2 × 103
0.135 0.666 5.60 9.27 13.95 18.25
0.407 2.14 14.9 21.4 28.8 30.8
Three-phase point (vapor, ethane-rich liquid, EG-rich liquid).
4. Discussion
Fig. 1. Experimental data for the EG (1) + ethane (2) system compared with correlated values using the Peng–Robinson equation.
The equilibrium data were correlated in the manner described by Jou et al. [3]. The method requires that an equation of state valid for the solvent and dilute solutions of the solute in the solvent be available. The Peng–Robinson [4] equation of state was used in the calculations. The parameters a22 and b2 of the ethane were obtained from the critical constants. The parameters a11 and b1 for EG were obtained from the vapor pressure and liquid density, as EG decomposes before reaching its critical temperature. The critical constants and acentric factors of the ethane and the equations for the vapor pressure and density of EG were taken from the compilation of Rowley et al. [5]. The resulting values of a11 and b1 for EG, and a22 and b2 for ethane are given in Table 2. The experimental solubility data were used to obtain the binary interaction parameter k12 which appears in the mixing rule of the equation of state: a12 = (a11 a22 )1/2 (1 − k12 )
3. Results The solubility of ethane in ethylene glycol was determined at the temperatures of 298.15, 323.15, 348.15, 373.15, and 398.15 K at pressures up to 20.3 MPa. The experimental data are presented in Table 1 and plotted in Fig. 1. At the lowest temperature, a sharp transition occurs between (vapor + liquid) and (liquid + liquid) equilibria. At higher pressures a liquid ethanerich phase is in equilibrium with the liquid glycol phase. At 298.15 K, there is a cusp at 4.21 MPa, which is the three-phase pressure where ethane-rich liquid, vapor and glycol-rich liquid coexist.
(1)
In two-phase regions, the isothermal flash routine algorithm presented by Whitson and Brul´e [6] was used. The binary interaction parameter was iteratively modified until the difference in the calculated and experimental liquid mole fractions was less than the set tolerance. Values of k12 were found to be dependent on the temperature and can be fitted by a linear relationship: k12 = 9.22 × 10−4 T (K) − 0.264
(2)
The correlation reproduces the experimental data with an overall average per cent deviation in the mole fraction of 2.1%, about the same as the experimental uncertainty.
Table 2 Equation of state parameters T (K)
298.15 323.15 348.15 373.15 398.15
Ethylene glycol (1)
k12
Ethane (2)
a11 (Pa m6 mol−2 )
b1 (cm3 mol−1 )
a22 (Pa m6 mol−2 )
b2 (cm3 mol−1 )
3.66 3.51 3.37 3.24 3.11
51.7 51.9 52.1 52.3 52.4
0.612 0.587 0.562 0.540 0.518
40.5 40.5 40.5 40.5 40.5
0.011 0.034 0.057 0.080 0.103
F.-Y. Jou et al. / Fluid Phase Equilibria 240 (2006) 220–223
222 Table 3 Calculated three-phase pressure and compositions
Table 4 Parameters of the Krichevsky–Ilinskaya equation
T (K) P (MPa) y1 × 106 x2␣ × 103  x1 × 103 P2s (MPa)
T (K)
H12 (MPa)
3 −1 v¯ ∞ 2 (cm mol )
A/RT
298.15 323.15 348.15 373.15 398.15
176.4 220.4 257.3 285.2 303.0
48.7 50.2 52.1 54.2 56.8
3.00 2.91 2.82 2.74 2.68
298.15 4.20 39 16 0.6 4.19
The binary interaction parameter, which was fit to the twophase data, and the pure component parameters were then used to predict a three-phase bubble point pressure. The three-phase bubble point calculation was performed with the three-phase bubble point technique described by Nutakki et al. [7] and Shinta and Firoozabadi [8]. Based on this technique and the abovementioned parameters, the calculated three-phase pressure and compositions are given in Table 3, together with the vapor pressure of pure ethane. The calculated mole fraction of ethane in the ethylene glycol phase is in good agreement with the experimental value given in Table 1. The vapor phase is essentially pure ethane and the calculated three-phase pressure is very close to the vapor pressure of pure ethane, and is lower than the experimental value. Gjaldbæk and Niemann [9] measured the solubility of ethane in ethylene glycol at atmospheric pressure (0.103 MPa) and 298.15 and 308.15 K. Using the pure component parameters in Table 2 and the binary interaction parameter, the liquid mole fraction was predicted. The overall predicted average absolute percentage deviation for both points was 5.3%, which is within the experimental uncertainty. Recently, Wang et al. [10] also performed experimental measurements for this system. Twenty data points were obtained at 283.2, 293.2 and 303.2 K at pressures up to 4.0 MPa. Unfortunately, there are no common temperatures to make a direct comparison. Again, using the pure component parameters in Table 2 and the binary interaction parameters from Eq. (2), the liquid mole fraction was predicted. The results are shown in Fig. 2 and it can be seen that there is a large difference between
Fig. 2. Experimental data of Wang et al. compared with calculated values using the Peng–Robinson equation.
the predicted values and the data of Wang et al., the overall predicted average absolute percentage deviation being 37.5%. The experimental procedure used by Wang et al. is similar to that employed in this work. However, they make no mention of correcting for the ethane dissolved in the glycol at atmospheric pressure. This could explain why their results are lower in mole fraction than the present work. Bender et al. [11] have shown the connection between the Peng–Robinson EOS, the binary interaction parameter and the three parameters in the Krichevsky–Ilinskaya equation. This equation is discussed in the book by Prausnitz et al. [12] and is given by: ∧ f2 v¯ ∞ (P − P1s ) A 2 ln = ln H21 + 2 (3) + (x − 1) x2 RT RT 1 The three parameters are the Henry’s constant, H21 , the partial molar volume at infinite dilution, and the Margules parameter, A. Recently, Schmidt [13] has corrected the equations which relate these parameters to the binary interaction parameter in the Peng–Robinson equation of state. The equations were used to obtain the three parameters and they are given in Table 4. The Henry’s constant for ethane in ethylene glycol is plotted in Fig. 3 for comparison with those for methane and propane. Also shown is the point obtained for ethane in ethylene glycol by Lenoir et al. [14]. It is much lower than the values for ethane obtained in the present work. Hayduk [15], in a critical review of solubility data for ethane in a number of solvents, concluded that the data presented by Lenoir et al. [14] are unreliable.
Fig. 3. The temperature dependence of the Henry’s constants for light hydrocarbons in EG.
F.-Y. Jou et al. / Fluid Phase Equilibria 240 (2006) 220–223
List of symbols a parameter in the Peng–Robinson equation (Pa m6 /mol2 ) A Margules parameter (J/mol) b parameter in the Peng–Robinson equation (cm3 /mol) ˆfi fugacity of component i in a mixture (kPa) H21 Henry’s constant of solute 2 in solvent 1 at P1s (MPa) kij binary interaction parameter in the Peng–Robinson equation Pis vapor pressure of component i (MPa) P pressure (MPa) R gas constant (J/mol K) T absolute temperature (K) v¯ ∞ partial molar volume at infinite dilution (cm3 /mol) 2 xi mole fraction of component i in the liquid phase yi mole fraction of component i in the vapor phase Superscripts ␣ ethylene glycol-rich phase  ethane-rich phase Acknowledgement The authors are grateful to the Natural Sciences and Engineering Research Council of Canada for financial support of this research.
223
References [1] F.-Y. Jou, F.D. Otto, A.E. Mather, Can. J. Chem. Eng. 72 (1994) 130–133. [2] F.-Y. Jou, F.D. Otto, A.E. Mather, J. Chem. Thermo. 25 (1993) 37–40. [3] F.-Y. Jou, R.D. Deshmukh, F.D. Otto, A.E. Mather, Fluid Phase Equilbr. 36 (1987) 121–140. [4] D.-Y. Peng, D.B. Robinson, Ind. Eng. Chem. Fundam. 15 (1976) 59–64. [5] R.L. Rowley, W.V. Wilding, J.L. Oscarson, Y. Yang, N.A. Zundel, T.E. Daubert, R.P. Danner, DIPPR Data Compilation of Pure Compound Properties, Design Institute for Physical Properties, AIChE, New York, USA, 2003. [6] C.H. Whitson, M.R. Brul´e, Phase behaviour, SPE Monograph Series 20, Society of Petroleum Engineers: Richardson, Texas, USA, 2000. [7] R. Nutakki, A. Firoozabadi, T.W. Wong, K. Aziz, SPE 17390, SPE/DOE Enhanced Oil Recovery Symposium, Tulsa, OK, USA, April 17–20, 1988. [8] A.A. Shinta, A. Firoozabadi, SPE Reserv. Eng. 12 (1997) 131–137. [9] J.C. Gjaldbæk, H. Niemann, Acta Chem. Scand. 12 (1958) 1015–1023. [10] L.-K. Wang, G.-J. Chen, G.-H. Han, X.-Q. Guo, T.-M. Guo, Fluid Phase Equilbr. 207 (2003) 143–154. [11] E. Bender, U. Klein, W.P. Schmitt, J.M. Prausnitz, Fluid Phase Equilbr. 15 (1984) 241–255. [12] J.M. Prausnitz, R.N. Lichtenthaler, E.G. de Azevedo, Molecular Thermodynamics of Fluid-phase Equilibria, 3rd ed., Prentice-Hall, Englewood Cliffs, NJ, 1999, p. 592. [13] K.A.G. Schmidt, Fluid Phase Equilbr. 236 (2005) 268–269. [14] J.-Y. Lenoir, P. Renault, H. Renon, J. Chem. Eng. Data 16 (1971) 340–342. [15] Hayduk, W., Ethane. IUPAC Solubility Data Series 9, Pergamon Press, Oxford, England, UK, 1982, p. 167.