Isothermal VaporâLiquid Equilibrium Data for Binary Systems of CHF3

Article Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX

pubs.acs.org/jced

Isothermal Vapor−Liquid Equilibrium Data for Binary Systems of CHF3 or C2F6 with Methylcyclohexane or Toluene Mark D. Williams-Wynn,* Paramespri Naidoo, and Deresh Ramjugernath Thermodynamics Research Unit, School of Engineering, University of KwaZulu-Natal, Howard College Campus, Durban, 4041, South Africa ABSTRACT: The isothermal vapor−liquid and vapor−liquid−liquid equilibria of four binary refrigerant−hydrocarbon systems were measured using a static-analytic apparatus at temperatures between 293.0 and 313.2 K and at pressures of up to 6.1 MPa. The two refrigerants that were investigated were trifluoromethane and hexafluoroethane, and the hydrocarbons were methylcyclohexane and toluene. At the temperatures that were investigated, the R-23 + toluene system alone did not exhibit any liquid−liquid immiscibility. The “bird’s-beak” phenomenon was observed for all of the systems. The experimental data were regressed with the PR MC EOS with the WS mixing rule. Either the NRTL or the UNIQUAC activity coefficient model was used within the WS mixing rule. A procedure for the calculation of the critical locus curves from thermodynamic models and an extrapolation technique for determining the mixture critical points from subcritical coexistence curves were employed. The van Konynenburg and Scott classifications of the four binary systems were discussed.

1. INTRODUCTION Carbon dioxide (CO2) is presently by far the most commonly used supercritical (SC) solvent.1 This is because it is nonflammable and nontoxic and is therefore generally perceived to be a “green” solvent. The major difficulty in the use of CO2 as a SC solvent is its lack of polarity, which inhibits the extraction of any larger polar molecules. Although there is some controversy2 surrounding the definition of polarity, CO2 with a dipole moment of D = 03 has been considered to be nonpolar for this investigation. However, the argument that, as CO2 exhibits a nontrivial quadrupole moment,4,5 it should rather be considered a polar solvent also bears gravitas. To overcome this lack of polarity, polar cosolvents, which improve the solubilities of larger components in the solvent, are added to the solvent.6 It is of interest to determine whether other gases exist which would provide better performance than CO2, for the extraction of the more polar solutes, without the need for the addition of polar cosolvents. The requirements of these alternative gases would include the need to be nonflammable and nontoxic, as is the case for CO2. As a part of a study into SC solvents that could replace CO2, the performances of two refrigerants, trifluoromethane (R-23) and hexafluoroethane (R-116), have been benchmarked with several different hydrocarbons, including n-alkanes7,8 as well as an alkene and a branched alkane.9 This current investigation expands the study to include the phase equilibria of R-23 or R-116 with either methylcyclohexane (MCH) or toluene. This study will expand the database to include the behavior of refrigerants with an aromatic and a cycloalkane. The phase equilibrium data for the four systems of R-23 + MCH, R-23 + toluene, R-116 + MCH, and R-116 + toluene were measured using a static-analytic high-pressure vapor−liquid equilibrium (VLE) apparatus at temperatures between 293.0 and 313.2 K. © XXXX American Chemical Society

2. EXPERIMENTAL SECTION 2.1. Materials and Chemicals. Both the MCH (C7H14, CAS Number 108-87-2) and the toluene (C7H8, CAS Number 108-88-3) were purchased from Sigma-Aldrich Co. LLC. The trifluoromethane (CHF3, CAS Number 75-46-7) and hexafluoroethane (C2F6, CAS Number 76-16-4) were purchased from A-Gas (South Africa) (Pty) Ltd. Helium (Baseline 5.0, CAS Number 7440-59-7), purchased from Afrox South Africa, was used as the carrier gas for composition analysis using a gas chromatograph (GC). In addition to being used to perform the composition analyses of the binary mixtures, the GC was also used to verify the purities of the four components, through the measurement of the individual peak area fractions. The suppliers of the chemicals, the stated purities, the GC peak area fractions, and the critical temperatures and pressures are tabulated in Table 1. The densities of the MCH and the toluene were measured using an Anton-Paar DMA 5000 density meter. The uncertainties from the density measurements were 0.09 kg·m−3, 0.1 K, and 0.1 kPa for density, temperature, and pressure, respectively. The measured densities were compared with data reported in the literature.10−16 The measured data and the literature data are reported in Table 2 and show a close agreement. The refractive indices of the MCH and the toluene were measured using an Atago RX7000 refractometer. This refractometer uses an LED light source that approximates the wavelength of the yellow sodium D-line, 589.0−589.6 nm. The uncertainties for these measurements were 6 × 10−4, 0.02 K, and 0.1 kPa for the refractive index, temperature, and pressure, respectively. The measured Received: February 7, 2018 Accepted: April 26, 2018

A

DOI: 10.1021/acs.jced.8b00123 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

Table 1. Pure Components: Suppliers, Stated Purities, GC Peak Area Fractions, Critical Temperatures, Tc, and Critical Pressures, Pc trifluoromethane, CHF3 hexafluoroethane, C2F6 methylcyclohexane, C7H14 toluene, C7H8 a

supplier

stated purity

GC area fraction

Tc (K)

Pc (MPa)

A-Gas (South Africa) (Pty) Ltd. A-Gas (South Africa) (Pty) Ltd. Sigma-Aldrich Co. LLC Sigma-Aldrich Co. LLC

>0.999d >0.999d >0.996e >0.995e

0.9996 0.9999 0.9989 0.9967

299.07c 293.03b 572.2c 591.79c

4.836c 3.013a 3.471c 4.104c

Kim.46 bSaikawa et al.47 cLide.48 dVolumetric basis. eMass basis.

Table 2. Experimentally Measured (exp.) Densities, ρ, of Methylcyclohexane and Toluene at Temperatures of T = 293.2−301.4 K and at Pressures of 99.6 kPa, Compared to Data Obtained from the Literature (lit.) methylcyclohexane

toluene

T (K)

ρ (lit.) (kg/m3)

ρ (exp.)h (kg/m3)

ρ (lit.) (kg/m3)

ρ (exp.)h (kg/m3)

293.2

769.39a

768.85

866.98a 866.55b

866.51

295.2 296.7 297.0 297.2 298.2

767.19 765.90 765.61 765.51 764.67

764.83c 765.01d 764.87e

probe had a maximum temperature uncertainty of 0.02 K. The maximum uncertainty in the calibration, at temperatures between 268.15 and 323.15 K, was found to be 0.06 K. A 0−25 MPa pressure transducer, also purchased from WIKA Instruments, was calibrated against a WIKA CPT 6000 pressure standard transducer. This standard pressure transducer had a maximum uncertainty of 6.2 kPa over its full span of 0−25 MPa. The calibration was performed at pressures between 0 and 10 MPa, giving a standard deviation of 0.5 kPa. The internal barometer of a Mensor CPC 3000 Pneumatic High-Speed Pressure Controller, with an uncertainty of 0.01 kPa, was used to measure the atmospheric pressure. For atmospheric pressure measurements using this barometer, the combined expanded uncertainty was estimated to be 0.1 kPa. The TCD of the GC was calibrated by relating the response of the TCD to the injection of known amounts of the chemicals through the GC. Several accurately known volumes of each component were injected into the GC with a syringe. This was repeated at least five times for each volume. The gases were injected with a 500 μL gastight SGE syringe, and the liquids were injected with a 1.0 μL SGE liquid syringe. According to the supplier, the uncertainties in the volumes injected using these syringes were 1 and 2% of the volume for the gases and liquids, respectively. However, for the estimation of the uncertainties, values of 2 and 4% were used for the gas and liquid syringes, respectively. The number of moles of gas that was injected was calculated via the ideal gas equation, and the number of moles of liquid injected was calculated using the liquid densities. 2.4. Experimental Procedure. The experimental procedure that was used to measure the data presented in this paper is similar to that which was presented by Nandi and co-workers.19 In-situ degassing was performed despite the purities of the gases and the measured GC area fractions for the gases being very near 1.0, as this ensured the removal of impurities that could have entered the cell during the loading procedure. An important change to the experimental procedure of Nandi and co-workers was the heating of the vaporization chamber of the ROLSI to 453 K during sampling. This was to ensure that the MCH and toluene were vaporized before being transferred to the GC for analysis. The higher temperature was required because of the relatively low volatilities of MCH and toluene. 2.5. Data Treatment. The guide to the expression of uncertainty in measurement (GUM)20 was used to estimate the uncertainties in the measured variables. The combined expanded uncertainties, calculated with a coverage factor of k = 2, were reported. The Peng−Robinson equation of state (PR EOS)21 with the Mathias−Copeman (MC) alpha function,22 coupled with the Wong−Sandler (WS) mixing rule,23 was used to model the systems. The Gibbs excess energy term within the mixing rule was described using either the non-random two-liquid (NRTL)24 or the universal quasi-chemical (UNIQUAC) activity coefficient model.25 The regression tool-kit within Aspen Plus V8.8 was used to regress the model parameters to the experimental data.

864.69

862.86 861.94

861.87e 862.11f 861.81g

298.7

861.45

́ Richon et al.11 bLi et al.10 cLoras et al.12 dCarmona et al.13 eMartinezSoria et al.14 fDomanska and Letcher.15 gSun et al.16 hU(T) = 0.1 K, U(P) = 0.1 kPa, and U(ρ) = 0.09 kg·m−3. a

refractive indices were compared with data from the literature10−15,17 in Table 3, and there was found to be a good agreement between the data sources. Table 3. Experimentally Measured (exp.) Refractive Indices (nD) of Methylcyclohexane and Toluene at Temperatures of T = 293.15−298.15 K and Pressures of 99.5 kPa, Compared to Data Obtained from the Literature (lit.) methylcyclohexane T (K) 293.15 298.15

nD (lit.) a

1.4231 1.42312b 1.4194c 1.4203d 1.4204e

nD (exp.)

toluene h,i

nD (lit.)

nD (exp.)h,i

1.4231

1.49693

b

1.4966

1.4206

1.4940e 1.49410f 1.49417g

1.4937

a

Richon et al.11 bRiddick et al.17 cLoras et al.12 dCarmona et al.13 ́ Martinez-Soria et al.14 fDomanska et al.15 gLi et al.10 hU(T) = 0.02 K, U(P) = 0.1 kPa, and U(nD) = 6 × 10−4. iMeasured at the wavelength of the yellow sodium D-line. e

2.2. Experimental Apparatus. The static-analytic highpressure VLE apparatus that was developed by Narasigadu et al.18 was used to perform these VLE measurements. This equipment was designed for the measurement of phase equilibria at temperatures between 253 and 473 K and at pressures of up to 17 MPa. Williams-Wynn and co-workers7 provided a detailed description of the apparatus. 2.3. Calibrations. The temperature probes, pressure transducer, and thermal conductivity detector (TCD) of the GC required calibration. The Pt100 temperature probes, obtained from WIKA Instruments, were calibrated against a WIKA CTH 6500 temperature standard probe. This temperature standard B



Article

(AARD). The equations used to determine these statistical terms are given by eqs 1 and 2.

Table 4. Mathias−Copeman Alpha Function Parameters (κi) for the Pure Components Investigated in This Study in the Temperaturer Range, T, Regressed from Literature Data κ1

T (K) b

trifluoromethane hexafluoroethanec methylcyclohexaned toluenee

252.93−299.07 273.10−292.90 273.15−323.13 283.10−333.15

0.776 0.777 0.712 0.744

κ2

κ3

a

a

0 0a 0.033 0.063

MRD(θ ) =

0 0a 0.193 0.122

AARD(θ ) =

100 Np

Np

∑

100 Np

θexp − θcalc

1 Np

∑ 1

θexp

(1)

|θexp − θcalc| θexp

(2)

where θ is the measured variable, the subscripts exp and calc represent the experimental and calculated data points, respectively, and Np is the number of data points in the set. Two methods were utilized for the estimation of the mixture critical points of the binary systems. The first method was the extended scaling law method of Ungerer et al.26 This method was applied to VLE data by El Ahmar et al.27 and relies on the availability of subcritical coexistence data, which is extrapolated to the critical point. The second critical point estimation technique was that of Heidemann and Khalil.28 Stockfleth and Dohrn29 provided an in-depth explanation of this technique, which requires a thermodynamic model, fitted to experimental

a

Set to zero for this study. bObtained from Williams-Wynn et al.7 Obtained from Williams-Wynn et al.8 dRegressed to literature data.30−37 eRegressed to literature data.10,30,38−44

c

The regression was performed by minimizing a modified Barker objective function using a Deming-type algorithm. Both the temperature-dependent and temperature-independent parameters for the models were regressed, and their performances were compared. The two statistical terms that were used to compare the performances of the different models were the mean relative deviation (MRD) and the absolute average relative deviation

Table 5. Experimental P−x1I−x1II−y1 Data with Combined Expanded Uncertainties (U) for the Binary System of R-23 (1) + Methylcyclohexane (2) at Temperatures of T = 293.03−313.23 Ka T (K)

U(T) (K)

P (MPa)

U(P) (MPa)

x1I

U(x1I)

293.03 293.03 293.03 293.04 293.04 293.04 293.03b 293.04 293.04 293.04 293.04 303.12 303.13 303.13 303.13 303.13 303.13 303.13b 303.13 303.14 303.14 303.14 313.23 313.23 313.23 313.23 313.22 313.22 313.22 313.23 313.22 313.23 313.22

0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.08 0.08 0.08 0.08 0.08 0.08 0.09 0.08 0.08 0.08 0.08 0.10 0.10 0.09 0.10 0.09 0.09 0.10 0.10 0.09 0.10 0.09

0.914 1.509 2.121 2.625 3.060 3.553 3.893 3.910 3.939 3.960 4.066 1.011 1.601 2.311 2.942 3.784 4.396 4.848 4.847 4.973 5.074 5.112 0.931 1.459 2.159 2.831 3.489 4.046 4.819 5.335 5.598 5.950 6.077

0.004 0.006 0.006 0.010 0.007 0.009 0.004 0.004 0.004 0.004 0.004 0.005 0.006 0.009 0.004 0.008 0.007 0.007 0.004 0.004 0.004 0.006 0.006 0.004 0.005 0.005 0.006 0.006 0.007 0.008 0.004 0.006 0.008

0.019 0.035 0.055 0.072 0.090 0.115 0.133 0.916 0.933 0.942 0.972 0.020 0.034 0.054 0.073 0.105 0.133 0.156 0.913 0.954 0.973 0.985 0.016 0.029 0.045 0.063 0.083 0.101 0.132 0.154 0.165 0.173 0.180

0.001 0.001 0.002 0.002 0.002 0.003 0.003 0.009 0.003 0.003 0.002 0.001 0.001 0.001 0.002 0.002 0.003 0.004 0.003 0.001 0.002 0.001 0.002 0.001 0.002 0.002 0.002 0.003 0.003 0.004 0.004 0.003 0.004

x1II

U(x1II)

0.898

0.004

0.911

0.005

y1

U(y1)

0.976 0.981 0.984 0.980 0.988 0.983 0.987 0.989 0.989 0.994 0.994 0.970 0.973 0.984 0.988 0.986 0.985 0.992 0.990 0.985 0.989 0.996 0.952 0.962 0.968 0.975 0.977 0.980 0.978 0.973 0.967 0.943 0.920

0.009 0.006 0.005 0.005 0.004 0.008 0.005 0.003 0.002 0.003 0.002 0.006 0.009 0.007 0.006 0.003 0.002 0.005 0.003 0.002 0.005 0.003 0.008 0.007 0.006 0.007 0.004 0.004 0.002 0.002 0.004 0.005 0.004

a The pressure, P, first liquid phase composition, x1I, second liquid phase composition, x1II, and vapor phase composition, y1, along with their corresponding uncertainties are reported. The combined expanded uncertainties were calculated with a coverage factor of k = 2. b VLLE data.

C



Article

Table 6. Experimental P−x1−y1 Data with Combined Expanded Uncertainties (U) for the Binary System of R-23 (1) + Toluene (2) at Temperatures of T = 293.04− 313.26 Ka T (K)

U(T) (K)

P (MPa)

U(P) (MPa)

x1

U(x1)

y1

U(y1)

293.04 293.06 293.05 293.07 293.07 293.06 293.07 293.05 293.05 293.06 293.06 293.05 303.10 303.10 303.12 303.13 303.13 303.13 303.13 303.12 303.12 303.12 303.13 313.24 313.23 313.23 313.23 313.23 313.23 313.23 313.22 313.22 313.22 313.24 313.26

0.07 0.07 0.07 0.07 0.08 0.07 0.07 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.10 0.10 0.10 0.10 0.09 0.10 0.09 0.10 0.09 0.10 0.09 0.09

0.847 1.376 1.999 2.481 2.976 3.199 3.400 3.487 3.593 3.790 4.035 4.114 0.908 1.429 2.000 3.232 3.680 3.980 4.198 4.339 4.460 4.813 5.037 0.834 1.675 2.397 3.238 3.960 4.534 4.886 5.083 5.213 5.413 5.605 5.698

0.004 0.004 0.005 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.006 0.005 0.007 0.006 0.005 0.005 0.004 0.004 0.009 0.004 0.004 0.006 0.006 0.006 0.006 0.006 0.005 0.004 0.007 0.004 0.004 0.006

0.041 0.077 0.135 0.196 0.306 0.404 0.538 0.660 0.740 0.868 0.958 0.987 0.038 0.065 0.104 0.231 0.324 0.440 0.576 0.713 0.788 0.914 0.969 0.029 0.066 0.106 0.171 0.247 0.346 0.462 0.565 0.659 0.767 0.837 0.898

0.001 0.002 0.004 0.004 0.005 0.005 0.005 0.005 0.005 0.003 0.002 0.001 0.001 0.001 0.002 0.004 0.005 0.005 0.005 0.004 0.004 0.003 0.002 0.001 0.001 0.002 0.002 0.004 0.005 0.005 0.005 0.005 0.004 0.004 0.002

0.977 0.981 0.987 0.988 0.988 0.988 0.992 0.992 0.991 0.994 0.998 0.998 0.965 0.977 0.984 0.986 0.987 0.987 0.987 0.989 0.988 0.994 0.997 0.940 0.974 0.980 0.979 0.980 0.979 0.977 0.976 0.976 0.973 0.967 0.967

0.004 0.003 0.005 0.004 0.003 0.003 0.002 0.002 0.004 0.003 0.002 0.001 0.002 0.003 0.003 0.002 0.003 0.002 0.004 0.002 0.003 0.002 0.005 0.005 0.002 0.0023 0.002 0.004 0.002 0.002 0.003 0.003 0.002 0.004 0.005

phase equilibrium data, to enable the mixture critical locus curves to be constructed. Williams-Wynn and co-workers7 have discussed both of these mixture critical point estimation techniques in greater detail.

3. RESULTS AND DISCUSSION The parameters for the MC alpha function were fitted to vapor pressure data that were reported in the literature for MCH30−37 and for toluene.10,30,38−44 The MC alpha parameters that were reported by Williams-Wynn et al.7,8 for R-23 and R-116 were used in this study. A one-parameter model was used for both R-23 and R-116, because of the measurement of some VLE data above the refrigerant critical temperatures, in which case the second and third terms of the model become trivial. The MC alpha function parameters that were used in this study are reported in Table 4. The measured phase equilibrium data for the four systems are reported in Tables 5−8. Alongside the isothermal P−x−x−y data presented in these tables are the estimated combined expanded uncertainties for each measured variable (temperature, pressure, and composition). The parameters for the PR MC + WS/NRTL and PR MC + WS/UNIQUAC thermodynamic models that were fitted to the experimental data are presented in Tables 9−12. Both the temperature-dependent and temperatureindependent parameters are reported. The statistical data for the regressions are included alongside the respective parameters. Table 13 contains several points along each of the four critical locus curves which were calculated using the procedure of Heidemann and Khalil. Additionally, the mixture critical points for three of the systems, calculated by the procedure of Ungerer et al., are also included in Table 13. The mixture critical points for the R-116 + toluene system at the temperatures measured were all in the liquid−liquid region. The extrapolation method of Ungerer and co-workers fails in the liquid−liquid equilibrium (LLE) region, and therefore, no extrapolated mixture critical points could be reported. The experimental P−x−x−y data for the four systems are plotted alongside the curves produced by the thermodynamic models in Figures 1−4. These figures also include the calculated critical locus curves (by the method of Heidemann and Khalil) and the extrapolated mixture critical points (by the method of Ungerer et al.). For the investigation into the temperature dependency of the thermodynamic models, the temperaturedependent and temperature-independent parameters for each system are plotted in Figures 5−8.

a

The pressure, P, liquid phase composition, x1, and vapor phase composition, y1, along with their corresponding uncertainties are reported. The combined expanded uncertainties were calculated with a coverage factor of k = 2.

Table 7. Experimental P−x1I−x1II−y1 Data with Combined Expanded Uncertainties (U) for the Binary System of R-116 (1) + Methylcyclohexane (2) at Temperatures of T = 293.10−313.15 Ka T (K)

U(T) (K)

P (MPa)

U(P) (MPa)

x1I

U(x1I)

293.11

0.11

0.941

0.004

0.030

293.10

0.10

1.240

0.004

0.038

293.10

0.09

1.517

0.006

293.10

0.09

1.871

293.10

0.09

293.12

0.11

293.11

x1II

U(x1II)

y1

U(y1)

0.003

0.974

0.003

0.003

0.982

0.004

0.046

0.002

0.980

0.002

0.008

0.061

0.004

0.985

0.003

2.164

0.007

0.074

0.003

0.984

0.004

2.464

0.004

0.088

0.003

0.983

0.003

0.10

2.737

0.004

0.103

0.004

0.987

0.005

293.11b

0.09

2.778

0.005

0.102

0.003

0.992

0.004

293.11

0.09

2.830

0.004

0.941

0.003

0.995

0.002

293.10

0.07

2.928

0.006

0.982

0.001

0.994

0.001

D

0.925

0.003



Article

Table 7. continued T (K)

U(T) (K)

P (MPa)

U(P) (MPa)

x1I

U(x1I)

293.11 303.11 303.11 303.11 303.11 303.10 303.11 303.12 303.12 303.12 303.12 303.12 303.12 313.14 313.14 313.15 313.14 313.13 313.14 313.13 313.14 313.13 313.13 313.12 313.12

0.08 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.07 0.06 0.06 0.06 0.07 0.07 0.07 0.07 0.07 0.06 0.07 0.06 0.06 0.05 0.06 0.06 0.07

3.010 0.912 1.129 1.342 1.667 1.990 2.337 2.651 2.966 3.212 3.384 3.451 3.486 0.962 1.264 1.516 1.994 2.416 2.807 3.057 3.361 3.656 3.819 3.972 4.220

0.007 0.005 0.004 0.004 0.005 0.005 0.007 0.006 0.004 0.006 0.004 0.004 0.009 0.004 0.004 0.005 0.005 0.007 0.005 0.004 0.006 0.006 0.006 0.005 0.005

0.994 0.028 0.037 0.041 0.052 0.065 0.075 0.086 0.100 0.107 0.118 0.121 0.123 0.029 0.038 0.045 0.064 0.078 0.093 0.102 0.112 0.124 0.128 0.131 0.134

0.001 0.001 0.002 0.002 0.002 0.003 0.003 0.003 0.004 0.004 0.004 0.004 0.003 0.002 0.002 0.002 0.002 0.003 0.003 0.003 0.003 0.004 0.004 0.005 0.004

x1II

U(x1II)

y1

U(y1)

0.998 0.942 0.971 0.978 0.975 0.981 0.978 0.978 0.982 0.983 0.977 0.971 0.960 0.971 0.975 0.976 0.978 0.982 0.973 0.979 0.976 0.976 0.976 0.977 0.966

0.002 0.005 0.004 0.005 0.004 0.005 0.004 0.002 0.003 0.005 0.004 0.005 0.006 0.002 0.002 0.004 0.005 0.006 0.010 0.004 0.005 0.004 0.004 0.003 0.004

a The pressure, P, first liquid phase composition, x1I, second liquid phase composition, x1II, and vapor phase composition, y1, along with their corresponding uncertainties are reported. The combined expanded uncertainties are calculated with the coverage factor k = 2. b VLLE data.

Table 8. Experimental P−x1I−x1II−y1 Data with Combined Expanded Uncertainties (U) for the Binary System of R-116 (1) + Toluene (2) at Temperatures of T = 293.10−313.12 Ka T (K)

U(T) (K)

P (MPa)

U(P) (MPa)

x1I

U(x1I)

293.11 293.11 293.10 293.10 293.11 293.11b 303.11 303.11 303.11 303.11 303.10 303.10 303.10 313.11 313.10 313.10 313.12 313.11 313.11 313.11

0.08 0.08 0.07 0.07 0.08 0.08 0.06 0.06 0.06 0.06 0.05 0.06 0.06 0.05 0.08 0.06 0.04 0.04 0.04 0.04

1.007 1.484 1.861 2.391 2.708 2.919 1.026 1.607 2.345 2.836 3.344 3.568 3.807 1.076 1.630 2.320 2.907 3.631 4.137 4.605

0.005 0.004 0.004 0.008 0.008 0.004 0.005 0.004 0.004 0.005 0.005 0.004 0.005 0.005 0.004 0.004 0.005 0.005 0.004 0.007

0.010 0.016 0.020 0.026 0.029 0.030 0.010 0.017 0.028 0.030 0.033 0.034 0.034 0.010 0.017 0.027 0.031 0.036 0.040 0.040

0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.002 0.002 0.002 0.002 0.003 0.002 0.003 0.004 0.002 0.003 0.003 0.003 0.003

x1II

0.997

U(x1II)

0.001

y1

U(y1)

0.970 0.984 0.989 0.991 0.994 0.995 0.966 0.982 0.987 0.990 0.992 0.987 0.981 0.977 0.982 0.979 0.986 0.988 0.987 0.980

0.008 0.004 0.002 0.002 0.002 0.003 0.004 0.005 0.004 0.002 0.002 0.003 0.005 0.006 0.002 0.004 0.005 0.002 0.004 0.004

The pressure, P, first liquid phase composition, x1I, second liquid phase composition, x1II, and vapor phase composition, y1, along with their corresponding uncertainties are reported. The combined expanded uncertainties are calculated with the coverage factor k = 2. b VLLE data. a

The phase equilibria of the R-23 + MCH system (Tables 5 and 9, Figures 1 and 5) exhibited a large miscibility gap, including vapor−liquid−liquid equilibrium (VLLE) points at the lower

two temperatures measured. At 313.2 K, only LLE was observed at the higher pressures, with no vapor phase being present. The pressure of the transition from VLLE to LLE was not E



Article

Table 9. Temperature-Dependent and Temperature-Independent Model Parameters (k12 and τij) and Regression Statistics for the Binary System of Trifluoromethane (1) + Methylcyclohexane (2)a MRDc T (K) temperature-independent

temperature-dependent

temperature-independent


293.0 303.1 313.2 293.0 303.1 313.2 293.0 303.1 313.2 293.0 303.1 313.2

k12 0.566 0.568 0.557 1.034

0.549 0.552 0.531 0.548

τ12 (K)

τ21 (K)

b

b

PR MC + WS/NRTL 1.023 2.375 0.951 2.320 1.002 2.209 1.070 2.352 0.562 2.273 1.001 2.200 PR MC + WS/UNIQUAC 1.180 0.104 1.202 0.109 1.195 0.113 1.183 0.105 1.176 0.113 1.170 0.121

AARDd

P

y1

P

y1

2.18 1.47 −1.39

−0.94 0.09 −0.98

2.58 2.90 2.40

0.94 1.24 3.58

0.50

−0.58

2.87

1.93

2.43 1.86 −0.90

−0.93 0.48 −0.66

2.78 3.05 1.92

0.93 1.60 3.71

0.69

−0.61

2.97

1.89

a

The temperature-dependent parameters were regressed at temperatures of T = 293.0−313.2 K. The mean relative deviations (MRDs) and the absolute average relative deviations (AARDs) in the pressure, P, and vapor mole fraction, y, are included for each of the regressions. bτ12, τ21 for the

NRTL and the UNIQUAC activity coefficient model. cMean relative deviation, MRD(θ ) = AARD(θ ) =

100 Np

100 Np

N θexp − θcalc d . Absolute θexp

∑1 p

average relative deviation,

N |θexp − θcalc| . θexp

∑1 p

Table 10. Temperature-Dependent and Temperature-Independent Model Parameters (k12 and τij) and Regression Statistics for the Binary System of Trifluoromethane (1) + Toluene (2)a MRD T (K) temperature-independent




293.0 303.1 313.2 293.0 303.1 313.2 293.0 303.1 313.2 293.0 303.1 313.2

k12 0.419 0.441 0.474 0.562

0.420 0.437 0.471 0.548

τ12 (K)

τ21 (K)

b

b


AARD

P

y1

P

y1

0.53 0.24 −2.55

−0.94 −1.12 −1.42

3.88 2.70 4.21

0.94 1.12 1.77

−2.18

−1.12

3.69

1.15

1.49 0.68 −2.51

−0.73 −1.00 −1.40

3.59 2.65 3.93

0.73 1.01 1.77

−0.29

−0.96

2.59

1.24

a

The temperature-dependent parameters were regressed at temperatures of T = 293.0−313.2 K. The mean relative deviations (MRDs) and the absolute average relative deviations (AARDs) in the pressure, P, and vapor mole fraction, y, are included for each of the regressions. bτ12, τ21 for the NRTL and the UNIQUAC activity coefficient models.

calculation being dependent upon the thermodynamic model. Any discrepancies between the experimental data and the model were therefore projected onto the critical locus curve. Only a single mixture critical point could be extrapolated for this system, again due to the method of Ungerer and co-workers only being applicable to vapor−liquid critical points. Of the three isotherms that were measured, only the 293.0 K isotherm yielded vapor− liquid critical points. The other two isotherms exhibited liquid− liquid critical points. The thermodynamic models provided reasonable descriptions of the three isotherms at which experimental data were measured for the R-23 + toluene system (Tables 6 and 10, Figures 2 and 6). The 293.1 and 303.1 K bubble point curves were modeled fairly well, but the models did not provide a good description of the 313.2 K isotherm. For this system, there was once

measured in this study. The thermodynamic models provided a reasonable description of the system. The description of the bubble point curve by the models was fairly accurate, but the modeled vapor phase compositions were between 0.01 and 0.03 higher than the experimental values. Despite these deviations being further accentuated in the expanded view of the P−x−x−y plot, they were still greater than the expanded experimental uncertainties. The models provided good estimates of the VLLE, which occurred at the lower temperatures, and the occurrence of the “bird’s-beak” phenomenon at compositions near pure R-23. There was little difference between the performances of the two thermodynamic models for this system. There was a substantial difference between the critical locus curve and the extrapolated mixture critical point for the R-23 + MCH system. This was likely due to the critical locus curve F



Article

Table 11. Temperature-Dependent and Temperature-Independent Model Parameters (k12 and τij) and Regression Statistics for the Binary System of Hexafluoroethane (1) + Methylcyclohexane (2)a MRD T (K) temperature-independent




k12

293.1 303.1 313.1 293.1 303.1 313.1

0.407 0.423 0.355

293.1 303.1 313.1 293.1 303.1 313.1

0.405 0.421 0.362

0.411

0.407

τ12 (K)

τ21 (K)

b

b


AARD

P

y1

P

y1

0.95 0.67 0.45

−0.54 −1.22 −0.29

2.19 2.65 1.10

0.61 1.60 0.82

0.30

−0.29

4.84

1.46

0.92 0.64 0.37

−0.53 −1.22 −0.34

2.18 2.70 1.12

0.62 1.59 0.80

0.17

−0.50

6.12

1.23

a

The temperature-dependent parameters were regressed at temperatures of T = 293.1−313.1 K. The mean relative deviations (MRDs) and the absolute average relative deviations (AARDs) in the pressure, P, and vapor mole fraction, y, are included for each of the regressions. bτ12, τ21 for the NRTL or UNIQUAC activity coefficient models.

Table 12. Temperature-Dependent and Temperature-Independent Model Parameters (k12 and τij) and Regression Statistics for the Binary System of Hexafluoroethane (1) + Toluene (2)a MRD





T (K)

k12

293.1 303.1 313.1 293.1 303.1 313.1

0.765 0.364 0.366

293.1 303.1 313.1 293.1 303.1 313.1

0.721

0.750 0.350 0.352 0.709

τ12b (K)

τ21b (K)

PR MC + WS/NRTL −0.372 3.812 0.070 3.748 0.150 3.496 −0.070 3.417 −0.067 3.303 −0.065 3.196 PR MC + WS/UNIQUAC 1.816 0.146 1.605 0.155 1.559 0.173 1.611 0.187 1.586 0.198 1.562 0.209

AARD

P

y1

P

y1

−2.44 −0.12 0.30

−0.91 0.29 −0.20

3.54 5.12 4.71

0.91 1.39 0.87

−3.62

−1.15

6.76

1.15

−2.48 0.56 0.23

−0.99 −0.28 −0.20

3.41 4.29 4.62

0.99 0.81 0.86

−3.46

−1.13

8.23

1.13

a The temperature-dependent parameters were regressed at temperatures of T = 293.1−313.1 K. The mean relative deviations (MRDs) and absolute average relative deviations (AARDs) in the pressure, P, and vapor mole fraction, y, are included for each of the regressions. bτ12, τ21 for the NRTL or UNIQUAC activity coefficient models.

again little variance between the temperature-dependent and temperature-independent models. Both models overpredicted the dew point compositions at all three temperatures. This overprediction appeared to be worse at higher temperatures and lower pressures. Both models were, however, capable of modeling the “bird’s-beak” phenomenon which occurred at lower temperatures, at compositions near pure R-23. From the critical locus curve that was calculated for this system, it appeared that the 313.2 K isotherm may also exhibit the “bird’s-beak” phenomenon. This was because the extrapolated mixture critical point at 313.2 K appeared to be incorrect when compared against the critical locus curve. Alternatively, the critical locus curve was incorrect due to the poor description of the vapor phase by the model at 313.2 K. The “bird’s-beak” phenomenon was not observed experimentally, and therefore, the second possibility would appear to be the more likely.

The two systems involving R-116 both exhibited very large miscibility gaps. This was perhaps due to the molecules having very different polarities. R-116 has a dipole moment of zero,3 while the nonsymmetric MCH and toluene have small, nonzero, dipole moments,3 making them polar. The R-116 + MCH system (Tables 7 and 11, Figures 3 and 7) exhibited a vapor−liquid critical point, along with a three-phase VLLE region at 293.1 K, and liquid−liquid critical points for the other two isotherms. While the vapor phase composition at the lowest pressure for the 303.1 K isotherm appears to follow a different trend than that of the other two isotherms, the experiments and repeatability of the measured data confirmed the data reported in this paper. The thermodynamic models provided fairly accurate descriptions of the phase behavior of the system with the description of the dew point curve being more accurate with this system than with the systems containing R-23. It was found that G



Article

describe the VLLE and the “bird’s-beak” phenomenon for the 293.1 K isotherm more accurately. The critical locus curve was calculated for this system using the method of Heidemann and Khalil with the temperature-dependent thermodynamic model. The calculated critical locus curve agreed with the extrapolated mixture critical point. All three of the isotherms that were measured for the R-116 + toluene system (Tables 8 and 12, Figures 4 and 8) exhibited liquid−liquid critical points. Despite the compositions of the second liquid phase and the vapor phase for the VLLE data point at 293.1 K being statistically indistinguishable, visual observation confirmed that these were two separate phases. The poor miscibility of the R-116 and toluene made measurement of the VLE fairly challenging with the static-analytic cell. A variablevolume cell with sampling capabilities for both the liquid and vapor phases would have enabled the measurement of greater amounts of data for this system. The bubble point data of the three isotherms were very difficult to distinguish between, with the only tangible difference being the increased solubility of the R-116 in the toluene rich phase with increased temperature. The differences between the dew point curves of the three isotherms were larger than those of the bubble point curves. The models were not particularly capable of accurately modeling the phase behavior of the system, with the performances of the temperature-dependent models being worse than those of the temperature-independent models. This indicates that the temperature dependency of the thermodynamic models was not suited to these systems. This could have been due to the presence of polar components or due to the sizes of the molecules. The poor modeling of the phase behavior likely translated into a poor description of the critical locus curve. However, due to no isotherms exhibiting vapor−liquid critical points being measured, it was impossible to verify the critical locus curve with critical loci extrapolated from the subcritical coexistence data. The plots of the temperature-dependent and temperatureindependent parameters for the thermodynamic models

Table 13. Critical Locus Curves, Consisting of Critical Temperature, Tc, Critical Pressure, Pc, and the and the Critical Composition, xc, Estimated from the Thermodynamic Models by the Method of Heidemann and Khalil,28 and Extrapolated Mixture Critical Loci by the Method of Ungerer et al.26 Critical Locus Curves (Heidemann and Khalil) Tc (K)

Pc (MPa)

xc,1

R-23 (1) + Methylcyclohexane (2) 301.7 5.21 0.99 306.8 5.64 0.98 316.3 6.02 0.97 330.8 6.48 0.96 348.0 7.06 0.95 371.2 8.14 0.93 382.0 10.05 0.90 R-116 (1) + Methylcyclohexane (2) 300.2 3.43 0.99 306.7 3.74 0.98 312.7 4.05 0.97 319.8 4.40 0.96 326.6 4.76 0.95 364.1 6.54 0.90

Tc (K)

Pc (MPa)

xc,1

R-23 (1) + Toluene (2) 305.5 5.52 0.99 312.8 6.24 0.98 322.4 6.99 0.97 336.7 7.81 0.96 365.9 9.52 0.94 401.2 11.34 0.92

R-116 (1) + Toluene (2) 297.4 3.73 0.99 302.9 4.35 0.98 307.2 4.91 0.97 312.1 5.53 0.96 316.3 6.01 0.95 326.9 7.20 0.93 351.2 9.19 0.90 379.1 11.31 0.85 Critical Loci (Ungerer et al.)

Tc (K)

Pc (MPa)

xc,1

R-23 (1) + Methylcyclohexane (2) 303.1 5.18 0.997

Tc (K)

Pc (MPa)

xc,1

R-23 (1) + Toluene (2) 303.1 5.13 0.997 313.2 5.81 0.948

R-116 (1) + Methylcyclohexane (2) 293.1 3.03 0.998

the temperature-independent models were able to describe the system more accurately than the temperature-dependent models. In particular, the temperature-independent model was able to

Figure 1. P−x1I−x1II−y1 data for the binary system of trifluoromethane (1) + methylcyclohexane (2) at temperatures of (green ◇) 293.0 K, (yellow △) 303.1 K, and (red +) 313.2 K. Solid lines, PR MC + WS/NRTL model; dashed lines, PR MC + WS/UNIQUAC model; black □, mixture critical locus (Ungerer et al. method); black dotted lines, mixture critical locus curve (Heidemann and Khalil method). H



Article

Figure 2. P−x1−y1 data for the binary system of trifluoromethane (1) + toluene (2) at temperatures of (green ◇) 293.0 K, (yellow △) 303.1 K, and (red +) 313.2 K. Solid lines, PR MC + WS/NRTL model; dashed lines, PR MC + WS/UNIQUAC model; black □, mixture critical loci (Ungerer et al. method); black dotted lines, mixture critical locus curve (Heidemann and Khalil method).

Figure 3. P−x1I−x1II−y1 data for the binary system of hexafluoroethane (1) + methylcyclohexane (2) at temperatures of (green ◇) 293.1 K, (yellow △) 303.1 K, and (red +) 313.1 K. Solid lines, PR MC + WS/NRTL model; dashed lines, PR MC + WS/UNIQUAC model; black □, mixture critical locus (Ungerer et al. method); black dotted lines, mixture critical locus curve (Heidemann and Khalil method).

(Figures 5−8) reveal that the temperature dependency was, for the most part, sufficiently described using simple linear dependency of the models. In some cases, a substantial difference between the temperature-dependent and temperature-independent parameter sets occurred, but this may have been due to several factors surrounding the regression of the given parameter set, rather than due to the temperature dependency of the system. For the most part, the description of the phase behavior was not substantially different when using the temperaturedependent parameters as opposed to using the temperatureindependent parameters. The temperature-dependent parameters, however, have a distinct advantage over the temperatureindependent parameters, in that they can be applied to any temperature within the range of the experimental data to which they were regressed.

Since only three isotherms were measured per system, it was difficult to precisely characterize the systems according to the van Konynenburg and Scott45 classification scheme. There were, however, a number of characteristics that could be used to shortlist the possible types that these systems could be classified as. All four systems exhibited liquid−liquid immiscibility and therefore could not be classified as type I systems. Additionally, the systems presented liquid−liquid critical loci at certain temperatures and could therefore not be classified as type II systems. Thus, the systems were most likely either type III, type IV, or type V systems. Measurement of the systems under conditions near the critical point of the heavier components would enable further classification of the systems from a P−T plot. This would make it possible to determine whether the critical locus curve emanating from the critical point of the I



Article

Figure 4. P−x−y data for the binary system of hexafluoroethane (1) + toluene (2) at temperatures of (green ◇) 293.1 K, (yellow △) 303.1 K, and (red +) 313.1 K. Solid lines, PR MC + WS/NRTL model; dashed lines, PR MC + WS/UNIQUAC model; black dotted lines, mixture critical locus curve (Heidemann and Khalil method).

Figure 5. Thermodynamic model parameters for the system of R-23 (1) + methylcyclohexane (2) with the temperature-independent parameters represented by symbols and the temperature-dependent parameters represented by lines. Left: PR MC + WS/NRTL; green ■/green dashed line, k12; black ●/black dotted line, τ12; red ▲/red solid line, τ21. Right: PR MC + WS/UNIQUAC; green ■/green dashed line, k12; ●/black dotted line, τ12; red ▲/red solid line, τ21.

heavier component traversed to the lower critical end point (LCEP) (for type IV or V systems) or to a critical point at infinite pressure (type III systems). To distinguish between type IV and type V systems would require a search for a low temperature upper critical solution temperature (UCST).

The PR MC + WS/NRTL and PR MC + WS/UNIQUAC thermodynamic models were fitted to the experimental data and found to provide adequate descriptions of the phase behavior. There was little difference between the two thermodynamic models or between the temperature-dependent and temperature-independent forms of the models. The performances of the models were poorest in their description of the vapor phase compositions. The critical locus curves were calculated from the temperature-dependent models by the method of Heidemann and Khalil and compared to the critical loci extrapolated from the experimental data by the method of Ungerer and co-workers. The agreement between the critical locus curves and the critical loci was closest at locations nearest to the critical point of component 1. The classification of the systems according to the van Konynenburg and Scott technique was discussed, and several of the classification types were shortlisted for these systems.

4. CONCLUSIONS A static-analytic high-pressure phase equilibrium apparatus was used to measure VLE and VLLE for four binary refrigerant + hydrocarbon systems at temperatures between 293.0 and 313.3 K. The four systems that were measured were R-23 + MCH, R-23 + toluene, R-116 + MCH, and R-116 + toluene. Only the R-23 + toluene system did not exhibit liquid−liquid immiscibility at the temperatures that were studied. The “bird’s-beak” phenomenon occurred near the critical point for three of the systems, with only R-116 + toluene not displaying this behavior. J



Article

Figure 6. Thermodynamic model parameters for the system of R-23 (1) + toluene (2) with the temperature-independent parameters represented by symbols and the temperature-dependent parameters represented by lines. Left: PR MC + WS/NRTL; green ■/green dashed line, k12; black ●/black dotted line, τ12; red ▲/red solid line, τ21. Right: PR MC + WS/UNIQUAC; green ■/green dashed line, k12; black ●/black dotted line, τ12; red ▲/red solid line, τ21.

Figure 7. Thermodynamic model parameters for the system of R-116 (1) + methylcyclohexane (2) with the temperature-independent parameters represented by symbols , and the temperature-dependent parameters represented by lines. Left: PR MC + WS/NRTL; green ■/green dashed line, k12; black ●/black dotted line, τ12; red ▲/red solid line, τ21. Right: PR MC + WS/UNIQUAC; green ■/green dashed line, k12; black ●/black dotted line, τ12; red ▲/red solid line, τ21.

Figure 8. Thermodynamic model parameters for the system of R-116 (1) + toluene (2) with the temperature-independent parameters represented by symbols and the temperature-dependent parameters represented by lines. Left: PR MC + WS/NRTL; green ■/green dashed line, k12; black ●/black dotted line, τ12; red ▲/red solid line, τ21. Right: PR MC + WS/UNIQUAC; green ■/green dashed line, k12; black ●/black dotted line, τ12; red ▲/red solid line, τ21. K



■

Article

Isooctane, and + Methylcyclohexane at 101.3 kPa. J. Chem. Eng. Data 1999, 44, 148−151. (15) Domanska, U.; Letcher, T. M. (Solid-liquid) equilibria and solid compound formation in (N-methyl-2-pyrrolidinone & benzene, or toluene, or 1,3,5-trimethylbenzene, or ethylbenzene, or chlorobenzene, or 1,2-dichlorobenzene, or 1,2,4-trichlorobenzene, or 1,1,1-trichloroethane, or dichloromethane). J. Chem. Thermodyn. 2000, 32, 1635− 1645. (16) Sun, Y.; Su, L.; Wang, H. Volumetric properties of binary liquid mixtures: Application of the Prigogine−Flory−Patterson theory to excess molar volumes of dichloromethane with benzene or toluene. J. Chem. Thermodyn. 2009, 41, 1154−1161. (17) Riddick, J. A.; Bunger, W. B.; Sakano, T. K. Organic Solvents: Physical Properties and Methods of Purification Techniques of Chemistry, 4th ed.; Wiley: New York, 1986; Vol. 2. (18) Narasigadu, C.; Naidoo, P.; Coquelet, C.; Richon, D.; Ramjugernath, D. A novel static analytical apparatus for phase equilibrium measurements. Fluid Phase Equilib. 2013, 338, 188−196. (19) Nandi, P.; Moodley, S.; Ramjugernath, D. Isothermal vapor− liquid equilibrium of R170 + perfluorooctane at 308−338 K: Measurement, equation of state modelling, and molecular simulation. Fluid Phase Equilib. 2013, 344, 84−91. (20) BIPM Joint Committee for Guides in Metrology. Evaluation of measurement data − Guide to the expression of uncertainty in measurement JCGM 100:2008 (GUM 1995 with minor corrections). BIPM: Paris, France, 2008; Vol. JCGM 100: 2008. (21) Peng, D. Y.; Robinson, D. B. A New Two-Constant Equation of State. Ind. Eng. Chem. Fundam. 1976, 15, 59−64. (22) Mathias, P. M.; Copeman, T. W. Extension of the Peng-Robinson Equation of State to Complex Mixtures: Evaluation of the Various Forms of the Local Composition Concept. Fluid Phase Equilib. 1983, 13, 91−108. (23) Wong, D. S. H.; Sandler, S. I. Theoretically Correct Mixing Rule for Cubic Equations of State. AIChE J. 1992, 38, 671−680. (24) Renon, H.; Prausnitz, J. M. Local Compositions in Thermodynamic Excess Functions for Liquid Mixtures. AIChE J. 1968, 14, 135− 144. (25) Abrams, D. S.; Prausnitz, J. M. Statistical thermodynamics of liquid mixtures: A new expression for the excess Gibbs energy of partly or completely miscible systems. AIChE J. 1975, 21, 116−128. (26) Ungerer, P.; Tavitian, B.; Boutin, A. Applications of molecular simulation in the oil and gas industry- Monte Carlo methods; IFP Publications: Paris, 2005. (27) El Ahmar, E.; Valtz, A.; Naidoo, P.; Coquelet, C.; Ramjugernath, D. Isothermal Vapor−Liquid Equilibrium Data for the Perfluorobutane (R610) + Ethane System at Temperatures from (263 to 353) K. J. Chem. Eng. Data 2011, 56, 1918−1924. (28) Heidemann, R. A.; Khalil, A. M. The calculation of critical points. AIChE J. 1980, 26, 769−779. (29) Stockfleth, R.; Dohrn, R. An algorithm for calculating critical points in multicomponents mixtures. Fluid Phase Equilib. 1998, 145, 43−52. (30) Willingham, C. B.; Taylor, W. J.; Pignocco, J. M.; Rossini, F. D. Vapor Pressures and Boiling Points of Some Paraffin, Alkylcyclopentane, Alkylcyclohexane and Alkylbenzene Hydrocarbons. J. Res. Natl. Bur. Stand. 1945, 35, 219. (31) Bonhorst, C. W.; Althouse, P. M.; Triebold, H. O. Esters of Naturally Occurring Fatty Acids - Physical Properties of Methyl, Propyl, and Isopropyl Esters of C6 to C18 Saturated Fatty Acids. Ind. Eng. Chem. 1948, 40, 2379−2384. (32) Nicolini, E.; Laffitte, P. C. Vapor Pressure of Some Pure Organic Liquids. C. R. Hebd. Seances Acad. Sci. 1949, 229, 757−759. (33) Heady, R. B.; Cahn, J. W. Experimental test of classical nucleation theory in a liquid-liquid miscibility gap system. J. Chem. Phys. 1973, 58, 896−910. (34) Castellari, C.; Francesconi, R.; Comelli, F. Vapor-liquid equilibrium, excess gibbs energy and excess enthalpy of 1,3-dioxolanemethylcyclohexane at T = 313.15 K. Can. J. Chem. Eng. 1988, 66, 131− 135.

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone: +27 31 2602938. Fax: +27 31 2601118. ORCID

Mark D. Williams-Wynn: 0000-0002-9751-5419 Deresh Ramjugernath: 0000-0003-3447-7846 Funding

This work is based upon research supported by the South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS The authors would like to thank the NRF Focus Area Programme and the NRF Thuthuka Programme. Opinions expressed and conclusions arrived at are those of the authors and are not necessarily to be attributed to the NRF.

■

REFERENCES

(1) Beckman, E. J. Supercritical and near-critical CO2 in green chemical synthesis and processing. J. Supercrit. Fluids 2004, 28, 121− 191. (2) Raveendran, P.; Ikushima, Y.; Wallen, S. L. Polar attributes of supercritical carbon dioxide. Acc. Chem. Res. 2005, 38, 478−485. (3) NIST ThermoData Engine. NIST ThermoData Engine 103b Pure Compounds, Binary Mixtures, and Chemical Reactions. Thermodynamics Research Centre, Ed. Boulder, CO, USA, 2013. (4) Perevalov, V. I.; Lobodenko, E. I.; Lyulin, O. M.; Teffo, J. L. Effective Dipole Moment and Band Intensities Problem for Carbon Dioxide. J. Mol. Spectrosc. 1995, 171, 435−452. (5) Williams, J. H. The molecular electric quadrupole moment and solid-state architecture. Acc. Chem. Res. 1993, 26, 593−598. (6) Brunner, G. Selectivity of supercritical compounds and entrainers with respect to model substances. Fluid Phase Equilib. 1983, 10, 289− 298. (7) Williams-Wynn, M. D.; Naidoo, P.; Ramjugernath, D. Isothermal (vapor + liquid) equilibrium data for binary systems of (n-hexane + CO2 or CHF3). J. Chem. Thermodyn. 2016, 94, 31−42. (8) Williams-Wynn, M. D.; Naidoo, P.; Ramjugernath, D. Isothermal vapor-liquid equilibrium data for the binary systems of (CHF3 or C2F6) and n-heptane. J. Chem. Thermodyn. 2016, 102, 237−247. (9) Williams-Wynn, M. D.; Naidoo, P.; Ramjugernath, D. Isothermal vapor-liquid equilibrium data for binary systems of (CHF3 or C2F6) with (1-hexene or 3-methylpentane). J. Chem. Thermodyn. 2018, 121, 79−90. (10) Li, I. P. C.; Wong, Y.-W.; Chang, S.-D.; Lu, B. C. Y. Vapor-liquid equilibriums in systems n-hexane-benzene and n-pentane-toluene. J. Chem. Eng. Data 1972, 17, 492−498. (11) Richon, D.; Laugier, S.; Renon, H. High-pressure vapor-liquid equilibria for binary mixtures containing a light paraffin and an aromatic compound or a naphthene in the range 313−473 K. J. Chem. Eng. Data 1991, 36, 104−111. (12) Loras, S.; Montón, J. B.; España, F. Vapor−Liquid Equilibria for the Binary Systems of Methylcyclohexane with 1-Propanol, 2-Propanol, 1-Butanol, and 2-Butanol at 101.3 kPa. J. Chem. Eng. Data 1997, 42, 914−918. (13) Carmona, F. J.; González, J. A.; García de la Fuente, I.; Cobos, J. C. Thermodynamic Properties of N-Alkoxyethanols + Organic Solvent Mixtures. X. Liquid−Liquid Equilibria of Systems Containing 2Methoxyethanol, 2-(2-Methoxyethoxy)ethanol or 2-(2-Ethoxyethoxy)ethanol, and Selected Alkanes. J. Chem. Eng. Data 1999, 44, 892−895. (14) Martínez-Soria, V.; Peña, M. P.; Montón, J. B. Vapor−Liquid Equilibria for the Binary Systems tert-Butyl Alcohol + Toluene, + L



Article

(35) Wu, H. S.; Pividal, K. A.; Sandler, S. I. Vapor-liquid equilibria of hydrocarbons and fuel oxygenates. J. Chem. Eng. Data 1991, 36, 418− 421. (36) Pividal, K. A.; Sterner, C.; Sandler, S. I.; Orbey, H. Vapor-liquid equilibrium from infinite dilution activity coefficients: measurement and prediction of oxygenated fuel additives with alkanes. Fluid Phase Equilib. 1992, 72, 227−250. (37) Mokbel, I.; Rauzy, E.; Loiseleur, H.; Berro, C.; Jose, J. Vapor pressures of 12 alkylcyclohexanes, cyclopentane, butylcyclopentane and trans-decahydronaphthalene down to 0.5 Pa. Experimental results, correlation and prediction by an equation of state. Fluid Phase Equilib. 1995, 108, 103−120. (38) Kahlbaum, G. W. A. The dependence of boiling temperature on the atmospheric pressure. Ber. Dtsch. Chem. Ges. 1884, 17, 1245−1262. (39) Kahlbaum, G. W. A. Studies on Vapor Pressure Measurements: II. Z. Phys. Chem.-Stoch. Ve. 1898, 26. (40) Woringer, B. Vapor Pressures of a Series of Benzene Derivatives. Z. Phys. Chem.-Stoch. Ve. 1900, 34, 257. (41) Forziati, A. F.; Norris, W. R.; Rossini, F. D. Vapor pressures and boiling points of sixty API-NBS hydrocarbons. J. Res. Natl. Bur. Stand. 1949, 43, 555−564. (42) Besley, L. M. Vapour pressure of toluence from 273.15 to 298.15 K. J. Chem. Thermodyn. 1974, 6, 577−580. (43) Mokbel, I.; Rauzy, E.; Meille, J. P.; Jose, J. Low vapor pressures of 12 aromatic hydrocarbons. Experimental and calculated data using a group contribution method. Fluid Phase Equilib. 1998, 147, 271−284. (44) Negadi, L.; Mokbel, I.; Negadi, A.; Kaci, A. A.; Jose, J.; Gmehling, J. Isothermal Vapor−Liquid Equilibria and Excess Enthalpy Data for the Binary System (Butyric Acid + Toluene). J. Chem. Eng. Data 2009, 54, 2045−2048. (45) van Konynenburg, P. H.; Scott, R. L. Critical Lines and Phase Equilibria in Binary Van Der Waals Mixtures. Philos. Trans. R. Soc., A 1980, 298, 495−540. (46) Kim, K. Y. Calorimetric studies on argon and hexafluoroethane and a generalized correlation of maxima in isobaric heat capacity. Ph.D. Dissertation, University of Michigan, Ann Arbor, MI, 1974. (47) Saikawa, K.; Kijima, J.; Uematsu, M.; Watanabe, K. Determination of the critical temperature and density of hexafluoroethane. J. Chem. Eng. Data 1979, 24, 165−167. (48) Lide, D. R. CRC Handbook of Chemistry and Physics 2004−2005; CRC Press LLC: Boca Raton, FL, 2004.

M


Isothermal VaporâLiquid Equilibrium Data for Binary Systems of CHF3

Recommend Documents

Isothermal VaporâLiquid Equilibrium Data for Binary Systems of CHF3