Experimental Determination and Prediction of Gas ... - ACS Publications

Ind. Eng. Chem. Res. 2002, 41, 4393-4398

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GENERAL RESEARCH Experimental Determination and Prediction of Gas Solubility Data for CO2 + H2O Mixtures Containing NaCl or KCl at Temperatures between 313 and 393 K and Pressures up to 10 MPa Jo1 rn Kiepe,† Sven Horstmann,‡ Kai Fischer,‡ and Ju 1 rgen Gmehling*,† Department of Industrial Chemistry, University of Oldenburg, P.O. Box 2503, D-26111 Oldenburg, Germany, and Laboratory for Thermophysical Properties (LTP GmbH), Institute at the University of Oldenburg, P.O. Box 2503, D-26111 Oldenburg, Germany

Gas solubility data of carbon dioxide (CO2) in water (H2O) and aqueous sodium or potassium chloride (NaCl, KCl) solutions were measured by means of the static synthetic method in a temperature range from 313 to 393 K and pressures up to 10 MPa. The experimental data were compared to the results of other authors and to calculated values using an equation of state (EoS) approach. The calculations were enabled by the combination of the PSRK group contribution EoS with the LIFAC method for the prediction of vapor-liquid-phase equilibria containing strong electrolytes. The required interaction parameters were fitted to experimental data from this work and from the literature. 1. Introduction Reliable information on the phase equilibrium behavior is required for the design and optimization of thermal separation processes (e.g., absorption columns) and chemical conversion processes (e.g., gas-liquid reactors) as an important topic in chemical engineering. The predictive Soave-Redlich-Kwong (PSRK) group contribution equation of state (EoS) proposed by Holderbaum and Gmehling1 is widely used in common simulation software for the prediction of vapor-liquid equilibria (VLE) and gas solubilities of nonelectrolyte systems, regardless of whether the systems are nonpolar or polar, sub- or supercritical, symmetric, or highly asymmetric.2-6 In the PSRK model, the advantages of EoS are combined with the local composition concept and the group contribution approach UNIFAC.7 A survey about the current status and the potential of this group contribution EoS is given by Horstmann et al.8 In many cases, e.g., in petroleum refining, gas processing industry, coal gasification, environmental protection, gas antisolvent salt crystallization, petroleum and natural gas exploitation, formation of gas hydrates, and various absorption processes, the influence of electrolytes on the phase equilibrium behavior has to be considered for the design of the different industrial processes. One of the promising approaches to account for the salt effects in solutions is the LIQUAC model (Li et al.9). In this gE model for single- and mixed-solvent strong electrolyte systems, the contribution of the shortrange interactions to the excess Gibbs energy is described by the UNIQUAC model. This electrolyte gE * Corresponding author. E-mail: tech.chem.uni-oldenburg.de. † University of Oldenburg. ‡ Laboratory for Thermophysical Properties.

gmehling@

model was combined with the group contribution concept of UNIFAC by Yan et al.,10 resulting in the so-called LIFAC method. Both electrolyte models can be used to predict not only VLE for single- and mixed-solvent + salt systems but also osmotic coefficients and mean activity coefficients for water + salt systems. Recently, the LIFAC method was linked to the PSRK EoS by Li et al.11 in order to describe also strong electrolyte systems with supercritical compounds (e.g., gas solubility in salt-containing solvents). In this approach, the influence of strong electrolytes on the activity coefficients of the nonelectrolytes is considered using the LIFAC model in the PSRK mixing rule. The published group interaction parameters of the PSRK and the LIFAC model can be used directly, and only the gasion interaction parameters have to be fitted to experimental data. In this work, several gas solubility data (isothermal P-x data) for the systems CO2 + H2O, CO2 + H2O + NaCl and CO2 + H2O + KCl were measured with a static apparatus. The data are presented in comparison to the experimental results of other authors and calculations using the PSRK model. Whereas for the CO2 + H2O system a large number of experimental data are available, only a few CO2 solubility data in an aqueous salt mixture containing NaCl and KCl can be found in the literature.12-16 2. Experimental Section 2.1. Materials. Water was distilled twice and then degassed as described before.17 Carbon dioxide (Lu¨bke; purity 99.995%) was used without any further purification. Sodium chloride (Gru¨ssing; purity >99.5%) and potassium chloride (Scharlau; purity >99.5%) were dried in a vacuum oven at 80 °C. 2.2. Apparatus and Procedure. For the gas solubility measurements (isothermal P-x data), a static ap-

10.1021/ie020154i CCC: $22.00 © 2002 American Chemical Society Published on Web 07/19/2002

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Ind. Eng. Chem. Res., Vol. 41, No. 17, 2002

Table 1. Experimental Gas Solubility Data for the System CO2 (1) + H2O (2) 313.20 K

353.11 K

x1

P/kPa

x1

P/kPa

0.000 00 0.000 36 0.000 97 0.001 59 0.002 23 0.002 84 0.003 54 0.004 46 0.007 13 0.016 39 0.019 02 0.021 23 0.024 81

7.18 95.09 245.74 397.51 558.87 710.35 889.33 1124.8 1834.4 4667.1 5664.0 6643.8 9231.9

0.000 00 0.000 22 0.001 34 0.002 22 0.003 49 0.004 87 0.006 44 0.011 11 0.014 37 0.017 34

50.82 134.23 578.58 933.80 1458.2 2043.6 2728.9 4939.0 6699.9 8550.3

373.26 K

393.17 K

x1

P/kPa

x1

P/kPa

0.000 00 0.000 15 0.000 61 0.000 85 0.001 44 0.002 61 0.004 13 0.006 39 0.008 43 0.010 92 0.012 91 0.014 49 0.015 99

100.78 175.56 394.75 509.79 795.06 1369.2 2133.6 3317.1 4437.8 5884.7 7128.0 8186.9 9257.6

0.000 00 0.000 03 0.000 71 0.001 18 0.002 29 0.006 50 0.009 27

192.45 204.54 619.90 846.51 1534.5 4230.3 6322.6

paratus was used. The equipment and measurement procedure were previously described in detail.17,18 In this synthetic method, the system pressure is measured at

constant temperature for different overall compositions. The apparatus can be operated at temperatures between 200 and 500 K and pressures up to 15 MPa. To determine the global compositions, the quantities of pure substances charged into the stirred equilibrium cell have to be known precisely. The salts are weighted into the cell before evacuation and placement of the cell in a thermoregulated oil bath. The purified and degassed water and liquefied carbon dioxide are charged into the cell as compressed liquids using piston injectors (model 2200-801, Ruska), which allow the precise recording of volume differences. After equilibrium has been reached, the pressure inside the cell is measured with a pressure sensor (model PDCR 911, Druck; range 0-13.5 MPa) and the temperature is monitored with a Pt100 resistance thermometer (model 1560, Hart Scientific). The pressure sensor was calibrated with a pressure balance (model 21000, Desgranges & Huot). Because only temperature, pressure, total loadings, and total volumes are measured, the compositions of the coexisting phases have to be determined by evaluation of the raw data. This evaluation procedure is quite complex and described in detail by Fischer and Wilken.18 From the known solvent feed (water + salt), the liquid-phase volume is determined using precise information about the density of the electrolyte solution inside the equilibrium chamber. Therefore, liquid densities of water + salt mixtures were measured as a function of temperature and salt content using a vibrating tube densimeter (model DMA 4500, Anton Paar). These data will be published elsewhere.19 From the total volume of the cell, the remaining gas-phase volume can be calculated precisely. At given equilibrium conditions (temperature, gas-phase volume, and CO2 pressure), the

Table 2. Experimental Gas Solubility Data for the System CO2 (1) + H2O (2) + NaCl (3) at 40 °C and Different Salt Concentrations m ) 0.52 mol‚kg-1 water and T ) 313.38 K

m ) 2.50 mol‚kg-1 water and T ) 313.31 K


x1,salt-free

P/kPa

x1,salt-free

P/kPa

x1,salt-free

P/kPa

0.000 00 0.000 33 0.001 36 0.001 80 0.003 15 0.006 75 0.010 32 0.011 82 0.014 27 0.016 59 0.018 83 0.021 12

6.91 98.15 385.10 509.43 886.62 1998.2 3150.4 3681.8 4621.3 5624.7 6776.3 8434.3

0.000 00 0.000 51 0.001 24 0.002 01 0.003 04 0.004 46 0.006 17 0.008 61 0.010 89 0.012 72 0.014 31 0.015 17

6.63 208.15 501.25 818.23 1244.0 1860.8 2635.0 3844.1 5137.2 6373.0 7788.5 9128.9

0.000 00 0.000 33 0.000 68 0.001 01 0.001 49 0.002 22 0.004 03 0.006 57 0.008 98 0.010 29 0.010 80 0.011 20

6.43 189.32 379.98 560.98 835.66 1250.0 2335.3 4026.6 5977.9 7377.9 8122.1 9061.2

Table 3. Experimental Gas Solubility Data for the System CO2 (1) + H2O (2) + NaCl (3) at 80 °C and Different Salt Concentrations m ) 0.52 mol‚kg-1 water and T ) 353.08 K



x1,salt-free

P/kPa

x1,salt-free

P/kPa

x1,salt-free

P/kPa

0.000 00 0.000 37 0.001 01 0.001 68 0.002 73 0.003 83 0.005 22 0.007 06 0.010 80 0.015 07 0.016 36 0.017 51

46.74 227.19 547.26 877.25 1403.9 1958.9 2669.8 3633.2 5692.3 8334.8 9239.5 10100

0.000 00 0.000 59 0.001 01 0.001 72 0.002 72 0.003 57 0.005 32 0.006 60 0.007 89 0.009 02 0.010 91

43.54 453.82 764.40 1260.4 2004.2 2654.0 4082.3 5221.0 6469.7 7678.7 10061

0.000 00 0.000 53 0.000 94 0.001 36 0.001 86 0.002 53 0.003 65 0.004 49 0.005 61 0.007 03 0.007 95

42.53 545.88 950.25 1361.9 1865.6 2558.7 3801.3 4798.0 6241.3 8354.1 10010

Ind. Eng. Chem. Res., Vol. 41, No. 17, 2002 4395 Table 4. Experimental Gas Solubility Data for the System CO2 (1) + H2O (2) + KCl (3) at 40 °C and Different Salt Concentrations

Table 5. Experimental Gas Solubility Data for the System CO2 (1) + H2O (2) + KCl (3) at 80 °C and Different Salt Concentrations





x1,salt-free

P/kPa

x1,salt-free

P/kPa

x1,salt-free

P/kPa

x1,salt-free

P/kPa

0.000 00 0.000 31 0.000 69 0.001 48 0.002 30 0.003 00 0.003 92 0.005 80 0.012 81 0.016 39 0.019 18 0.021 74

7.11 92.00 196.56 418.11 647.75 846.26 1113.0 1664.3 3938.0 5314.0 6611.6 8279.0

0.000 00 0.000 39 0.000 94 0.001 51 0.002 17 0.002 91 0.003 77 0.005 77 0.010 76 0.016 37 0.020 31

6.77 126.55 295.60 472.15 676.37 909.60 1182.3 1831.0 3582.8 5969.1 8696.1

0.000 00 0.000 35 0.000 91 0.003 12 0.004 19 0.005 14 0.006 16 0.008 51 0.010 93 0.013 88 0.016 36 0.017 87

47.29 199.18 427.42 1423.5 1916.0 2356.8 2845.6 4017.2 5313.6 7064.6 8747.3 9913.7

0.000 00 0.000 56 0.001 14 0.001 92 0.002 83 0.003 76 0.005 42 0.008 14 0.010 72 0.012 71 0.014 46 0.016 10

46.10 303.30 574.97 945.64 1379.9 1835.3 2673.1 4128.6 5633.0 6907.3 8141.8 9448.3





x1,salt-free

P/kPa

x1,salt-free

P/kPa

x1,salt-free

P/kPa

x1,salt-free

P/kPa

0.000 00 0.000 85 0.001 29 0.001 86 0.002 52 0.003 22 0.004 99 0.010 91 0.013 71 0.016 93 0.018 20 0.019 01

6.62 277.22 418.54 606.62 823.95 1056.9 1665.0 3954.9 5267.7 7210.3 8353.4 9709.1

0.000 00 0.000 76 0.001 35 0.001 85 0.002 61 0.003 57 0.005 40 0.007 27 0.009 17 0.011 74 0.013 88 0.015 80

6.51 355.77 625.86 852.74 1198.6 1638.7 2486.0 3372.6 4300.1 5660.7 6987.8 8965.8

0.000 00 0.000 33 0.000 75 0.001 11 0.001 44 0.002 04 0.003 52 0.005 57 0.007 83 0.009 60 0.011 47 0.013 50

45.48 237.23 487.39 704.30 900.81 1261.9 2190.5 3549.4 5183.3 6600.6 8294.3 10508

0.000 00 0.000 34 0.000 62 0.000 94 0.001 35 0.001 89 0.002 31 0.004 25 0.005 86 0.006 72 0.007 55 0.008 70 0.009 31

44.36 315.60 530.94 788.20 1120.1 1566.6 1911.5 3642.1 5232.2 6167.4 7132.2 8638.3 9526.8

amounts of CO2 in the gas phase and, thus, also in the liquid phase are obtained. In this approach, several effects have an influence on the resulting liquid-phase compositions and derived Henry coefficients. These effects are the small amounts of solvents in the gas phase, the compressibility of the solvent under the gas pressure, the partial molar volume of the dissolved gas, and the solvent activity coefficient. They can be taken into account in two different ways as described by Fischer and Wilken.18 In the first method, all effects are considered in an iterative isothermal and isochoric algorithm by solving the mass and volume balances. The second method makes use of EoS models, which offer the advantage of automatically providing the auxiliary desired quantities given above. To test the reliability of the data treatment, both methods were applied to the raw data measured in this work and identical results were obtained. For the measurements presented in this paper, the optimum filling of the cell with liquid was found to be 70%. 3. Results and Discussion The experimental P-x data from this work are listed in Tables 1-5, which were obtained with the EoS raw data treatment approach mentioned above. From these data, Henry coefficients H12 were derived using the EoS data treatment approach by computing

f1 ) φ∞1 PS2 x1f0 x1

H12 ) lim

where f1 is the gas fugacity, x1 the gas mole fraction, φ1 the fugacity coefficient of the gas in the liquid phase, and PS2 the solvent vapor pressure. The values are given in Table 6.

Table 6. Henry Coefficients of CO2 in the Different Solutions m/ mol‚kg-1 water

Hcalc/ MPa (PSRK)

T/K

Hexp/ MPa

CO2 (1) + H2O (2)

0

313.20 353.11 373.26 393.17

243 391 471 547

236 396 476 549

CO2 (1) + H2O (2) + NaCl (3)

0.52

313.38 353.08 313.31 353.07 313.38 352.77

276 488 393 684 543 933

259 433 359 598 460 809

313.31 353.08 313.31 352.55 313.16 353.09 313.37 353.40

274 428 300 457 316 579 456 770

253 435 270 472 303 567 344 672

system

2.50 4.00 4.34 CO2 (1) + H2O (2) + KCl (3)

0.50 1.00 2.50 3.96 4.00

In Figure 1a, the experimental results for the saltfree system CO2 + water are compared with data taken from the literature20,21 and predictions using the PSRK group contribution EoS, whereby in Figure 1b an enlargement of the significant data is shown. As can be seen, the experimental data of this work are in good agreement with the data of other authors. Unfortunately, at high pressures (>5 MPa) the PSRK predictions using the original interaction parameters for CO2 + water show significant deviations to the experimental data. These parameters had been fitted to data covering a large temperature and pressure range in order to describe the global phase diagrams (including also gas-

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Figure 3. Experimental and predicted P-x data for the system CO2 (1) + H2O (2) + NaCl (3) at 40 °C: experimental data from this work are m ) 0 mol‚kg-1 water (]), m ) 0.52 mol‚kg-1 water (9), m ) 2.50 mol‚kg-1 water (b), and m ) 4.00 mol‚kg-1 water ([); that from work by Rumpf et al.15 is m ) 4.00 mol‚kg-1 water at 40 °C (+); PSRK parameters from Li et al.11 (- - -); PSRK parameters revised in this work (s).

Figure 1. Experimental and predicted P-x data for the system CO2 (1) + H2O (2): (a) experimental data from this work at 313.20 K (]), 353.11 K (0), 373.26 K (O), 393.15 K (∆); those from work by Fischer20 at 312.66 K (+); those from work by Mu¨ller21 at 393.17 K (*); original PSRK (- - -); PSRK parameters revised in this work (s); (b) enlargement of the significant area showing data taken from the literature.20,21 Figure 4. Experimental and predicted P-x data for the system CO2 (1) + H2O (2) + NaCl (3) at 80 °C: experimental data from this work are m ) 0 mol‚kg-1 water (0), m ) 0.52 mol‚kg-1 water (9), m ) 2.50 mol‚kg-1 water (b), and m ) 4.34 mol‚kg-1 water ([); that from work by Rumpf et al.15 is m ) 4.00 mol‚kg-1 water at 80 °C (+); PSRK parameters from Li et al.11 (- - -); PSRK parameters revised in this work (s).

Figure 2. Experimental and predicted Henry coefficients for CO2 (1) in H2O (2): experimental data from this work (9); different authors (Dortmund Data Bank, DDB 2001) (+); original PSRK (- - -); PSRK parameters revised in this work (s).

gas equilibria at very high pressures). This leads to less accurate results for the temperature range covered in this work. Because the salt effect is the departure from the salt-free system, a quantitative consideration of this effect requires one to start with the correct gas solubility

in the salt-free system CO2 + water. Therefore, this set of PSRK parameters was revised to a reduced database covering a limited temperature range in order to establish a consistent basis for the description of CO2 solubility data in aqueous electrolyte solutions. Experimental and predicted Henry coefficients are plotted in Figure 2 as a function of temperature. A typical temperature dependence of the Henry coefficients (and, thus, the solubility of CO2 in H2O) can be observed. The Henry coefficients increase with the temperature (and the solubility of CO2 reduces; compare Figure 1) until the maximum value is reached. A further increase of temperature again leads to decreasing values. The literature values are in good agreement with the Henry coefficients derived from the new data, which is also a proof for the reliability of the data measured in this work. The predicted values using the original PSRK parameters are able to describe the temperature dependence of the solubility qualitatively over the whole temperature range (250-650 K). Using the revised

Ind. Eng. Chem. Res., Vol. 41, No. 17, 2002 4397

Figure 5. Experimental and predicted Henry coefficients for CO2 (1) in H2O (2) + NaCl (3): experimental data from this work are 40 °C (b) and 80 °C (9); those compiled by Cramer16 are 35 °C (∆), 38 °C (×), 73.7 °C (]), 40.0 °C (+), 74.7 °C (0), and 82.1 °C (O); PSRK parameters revised in this work (s).

Figure 7. Experimental P-x data for the system CO2 (1) + H2O (2) + KCl (3) at 80 °C: experimental data from this work are m ) 0 mol‚kg-1 water (0), m ) 0.50 mol‚kg-1 water (9), m ) 1.00 mol‚kg-1 water (2), m ) 2.50 mol‚kg-1 water (b), and m ) 4.00 mol‚kg-1 water ([); PSRK parameters obtained in this work (s).

effect leading to larger Henry coefficients, i.e., smaller CO2 solubilities with increasing salt concentration, is observed (Table 6). Whereas the gas-ion interactions of Li et al.11 were fitted to the experimental solubility data of Rumpf et al.15 on the basis of the original PSRK parameters for CO2 + water, the new interaction parameters were fitted to all available experimental data for the system CO2 + water + NaCl based on the revised CO2-water interaction parameters. The calculated results using the PSRK model are included in the diagrams. The obtained parameters enable the reliable description of the solubility of CO2 in the electrolyte solution as a function of the NaCl concentration and the temperature. This is also illustrated in Figure 5, where the obtained experimental and predicted Henry coefficients are shown as a function of the molality and, furthermore, also compared to experimental data taken from the literature at similar temperatures and salt concentrations.16 This means that the PSRK model is able to describe the salt effect precisely, and the importance of an accurate representation of the saltfree system is emphasized. In Figures 6 and 7, the P-x data at 40 and 80 °C for the system CO2 + H2O + KCl are presented together with the calculated results using the PSRK interaction parameters fitted to the experimental data. For this system, the observed salt effect is smaller than that for the NaCl system, which can also be concluded from the Henry coefficients given in Table 6 and shown in Figure 8. For this system, the salting-out effect and its temperature dependence is also described steadily using the PSRK model. The interaction parameters for the PSRK model established in this work (short and middle range) are given in Tables 7 and 8. For the short-range (SR)

Figure 6. Experimental P-x data for the system CO2 (1) + H2O (2) + KCl (3) at 40 °C: experimental data from this work are m ) 0 mol‚kg-1 water (]), m ) 0.50 mol‚kg-1 water (9), m ) 1.00 mol‚kg-1 water (2), m ) 2.50 mol‚kg-1 water (b), and m ) 3.96 mol‚kg-1 water ([); PSRK parameters obtained in this work (s). Table 7. Revised Gas-Solvent Interaction Parameters for the PSRK Model Used in This Work i

j

aij/K

aji/K

bij

cij/K-1 cji/K-1

bji

CO2 H2O -26.409 -66.792 1.0749 1.2495

parameters, an improved description of the CO2 solubility in the desired range (270-470 K) is achieved, but the parameters should not be used for calculations at temperatures above 500 K. For the system CO2 + aqueous NaCl solution, experimental gas solubility data at several fixed salt concentrations were determined experimentally at 40 and 80 °C. In Figures 3 and 4, they are compared with data taken from the literature.18 It can be seen that the P-x data of Rumpf et al.15 at m ) 4 mol/kg are in excellent agreement with the data from this work. A salting-out Table 8. Gas-Ion Interaction Parameters for the PSRK Model

short-range (SR) interaction parameters

middle-range (MR) interaction parameters

i

j

aij/K

aji/K

bij

bji

Rij

βij

CO2a CO2a CO2b

ClNa+ K+

37.454 -205.37 630.19

38.100 67.178 -1060.0

-1.2733 0.109 84 4.4101

3.4101 -0.111 73 2.5230

0.235 04 -0.138 10 0.223 77

0.216 49 -0.124 94 0.396 71

a

Revised parameters. b New parameters.

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Figure 8. Experimental and predicted Henry coefficients for CO2 (1) in H2O (2) + KCl (3): experimental data from this work are 40 °C (b) and 80 °C (9); PSRK parameters obtained in this work (s).

parameters, the following temperature dependence is used:

parij ) aij + bijT where T and parij have the unit Kelvin. 4. Conclusions Accurate gas solubility data (isothermal P-x data) of CO2 in aqueous NaCl or KCl solutions were measured up to 10 MPa with a static apparatus. The reliability of our data was validated by a comparison with the experimental results from other authors. Interaction parameters for the PSRK method (gas-solvent and gas-ion interactions) were regressed to the new experimental data and data taken from the literature. The PSRK model was extended successfully to electrolyte systems by linking this model with the LIFAC model.11 The predicted results are in good agreement with the experimental data. The salting-out effect as well as the temperature dependence of the solubility behavior is represented correctly. Moreover, the observed results show that the synthetic method for the determination of gas solubility data is a suitable method to extend the database for the development of EoS models such as PSRK. Further measurements will be carried out soon in order to fill existing gaps in the PSRK parameter matrix. Acknowledgment The authors thank the “Bundesministerium fu¨r Wirtschaft” via “Arbeitsgemeinschaft industrieller Forschungsvereinigungen” (AIF project 12219N) for financial support. Literature Cited (1) Holderbaum, T.; Gmehling, J. PSRK: A group contribution equation of state based on UNIFAC. Fluid Phase Equilib. 1991, 70, 251-265.

(2) Fischer, K.; Gmehling, J. Further development, status and results of the PSRK method for the prediction of vapor-liquid equilibria and gas solubilities. Fluid Phase Equilib. 1996, 121, 185-206. (3) Gmehling, J.; Li, J.; Fischer, K. Further development of the PSRK model for the prediction of gas solubilities and vapor-liquidequilibria at low and high pressures. II. Fluid Phase Equilib. 1997, 141, 113-127. (4) Horstmann, S.; Fischer, K.; Gmehling, J. PSRK group contribution equation of state: revision and extension. III. Fluid Phase Equilib. 2000, 167, 173-186. (5) Li, J.; Fischer, K.; Gmehling, J. Prediction of vapor-liquid equilibria for asymmetric systems at low and high pressures with the PSRK model. Fluid Phase Equilib. 1998, 143, 71-82. (6) Horstmann, S. Theoretische und experimentelle Untersuchungen zum Hochdruckphasengleichgewichtsverhalten fluider Stoffgemische fu¨r die Erweiterung der PSRK-Gruppenbeitragszustandsgleichung. Thesis, Shaker, Aachen, Germany, 1999. (7) Hansen, H. K.; Rasmussen, P.; Fredenslund, A.; Schiller, M.; Gmehling, J. Vapor-liquid equilibria by UNIFAC groupcontribution. 5. revision and extension. Ind. Eng. Chem. Res. 1991, 30, 2352-2355. (8) Horstmann, S.; Fischer, F.; Gmehling, J. Application of PSRK for process design. Chem. Eng. Commun. 2002, in press. (9) Li, J.; Polka, H.-M.; Gmehling, J. A gE model for single and mixed solvent electrolyte systems. 1. Model and results for strong electrolytes. Fluid Phase Equilib. 1994, 94, 89-114. (10) Yan, W.; Topphoff, M.; Rose, C.; Gmehling, J. Prediction of vapor-liquid equilibria in mixed-solvent electrolyte systems using the group contribution concept. Fluid Phase Equilib. 1999, 162, 97-113. (11) Li, J.; Topphoff, M.; Fischer, K.; Gmehling, J. Prediction of gas solubilities in aqueous electrolyte systems using the predictive Soave-Redlich-Kwong model. Ind. Eng. Chem. Res. 2001, 40, 3703-3710. (12) Takenouchi, S.; Kennedy, G. C. The solubility of carbon dioxide in NaCl solutions at high temperatures and pressures. Am. J. Sci. 1965, 263, 445-454. (13) Yasunishi, A.; Yoshida, F. Solubility of Carbon Dioxide in Aqueous Electrolyte Solutions. J. Chem. Eng. Data 1979, 24, 1114. (14) Markham, A. E.; Kobe, K. A. The solubility of carbon dioxide and nitrous oxide in aqueous salt solutions. J. Am. Chem. Soc. 1941, 63, 449-454. (15) Rumpf, B.; Nicolaisen, H.; O ¨ cal, C.; Maurer, G. Solubility of carbon dioxide in aqueous solutions of sodium chloride: experimental results and correlation. J. Solution Chem. 1994, 23, 431448. (16) Cramer, S. D. The solubility of methane, carbon dioxide and oxygen in brines from 0 °C to 300 °C. (U.S.) Bureau of Mines Report of Investigations, National Technical Information Service (NTIS), 1982. (17) Fischer, K.; Gmehling, J. P-x and γ∞ data for the different binary butanol-water systems at 50 °C. J. Chem. Eng. Data 1994, 39, 309-315. (18) Fischer, K.; Wilken, M. Experimental determination of oxygen and nitrogen solubility in organic solvents up to 10 MPa at temperatures between 298 and 398 K. J. Chem. Thermodyn. 2002, 33, 1285-1308. (19) Kiepe, J.; Horstmann, S.; Gmehling, J. Experimental determination and correlation of density data for aqueous electrolyte mixtures. 2002, in preparation. (20) Fischer, K. Solubilities of carbon monoxide and carbon dioxide in N-methyl-pyrrolidone-2 and water. 2002, in preparation. (21) Mu¨ller, G. Experimentelle Untersuchungen des DampfFlu¨ssig-Gleichgewichts im System Ammoniak-KohlendioxidWasser zwischen 100 und 200 °C bei Dru¨cken bis 90 bar. Thesis, Kaiserslautern, 1983.

Received for review February 26, 2002 Revised manuscript received June 11, 2002 Accepted June 20, 2002 IE020154I

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