Article Cite This: J. Chem. Eng. Data XXXX, XXX, XXX-XXX
pubs.acs.org/jced
Binary Vapor−Liquid Equilibrium Data for Perfluorooctane with Light Gases (Oxygen, Nitrogen, and Methane) Mark Williams-Wynn,† Wayne Michael Nelson,*,† Zoubir Tebbal,‡ Paramespri Naidoo,† Latifa Negadi,‡,† and Deresh Ramjugernath† †
Thermodynamics Research Unit, School of Engineering, University of KwaZulu-Natal, Howard College Campus, King George V Avenue, 4041 Durban, South Africa ‡ LATA2M, Laboratoire de Thermodynamique Appliquée et Modélisation Moléculaire, University of Tlemcen, Post Office Box 119, Tlemcen 13000, Algeria S Supporting Information *
ABSTRACT: Experimental vapor−liquid equilibrium data are reported for the binary systems of perfluorooctane + either oxygen, nitrogen, or methane. Isothermal measurements were performed within the temperature range of 293.21 to 353.23 K, and at pressures up to 21 MPa, using two apparatuses; one based on the “static-analytic” method and the other on the “staticsynthetic” method. The experimental data were correlated using the perturbed-chain statistical associating fluid theory equation of state. The model provides a satisfactory representation of the experimental data within the measured temperature range.
these include the “innocuous” gases, such as nitrogen and oxygen. The solubilities of all possible components present in the flue gas are of importance for obtaining a precise understanding of the process, and the equilibrium behavior of such components with the perfluorocarbons also require investigation. Recently, a program of investigations into the phase equilibrium conditions of perfluorocarbons with common petroleum refinery gases has been undertaken through a collaboration between the Thermodynamics Research Unit and the LATA2M.12,13 In this study, the binary vapor−liquid−liquid equilibrium data for O2, N2, and methane in perfluorooctane were measured at temperatures between 293.21 and 353.23 K. The data were modeled using the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state (EOS), which may enable the prediction of the system phase behavior at temperatures outside of the measured ranges with reasonable accuracy.
1. INTRODUCTION The unique physical properties of perfluorocarbons (PFCs) have inspired the use of PFCs to be proposed in fields as diverse as environmental sciences, materials manufacture, and the medical industry.1−4 Due to high intramolecular forces within the molecules, and the low intermolecular forces between the molecules, this class of compounds is generally highly stable, with comparatively low viscosities, and possesses the ability to absorb gases more easily than other liquids.5,6 A significant drive behind the investigation into new uses for perfluorocarbons extends from South Africa’s ambitions to develop new uses of either fluorine in its pure form, or alternatively chemicals that contain fluorine as a part of their molecule.7 The field of fluorine chemistry is of interest in South Africa because of the large reserves of acid grade fluorspar available. Only a small percentage of the fluorspar that is mined in South Africa is processed locally, while the majority is exported in its crude form. It is therefore desirable to develop novel uses for fluorinated compounds, to allow greater exploitation of these fluorspar reserves. The ability of perfluorocarbons to absorb more gases than other liquids with similar properties have rendered them interesting for use in flue gas treatment. A few studies involving phase equilibria of perfluorocarbons and components, such as carbon dioxide, nitric oxides, and hydrogen sulfide, which are present in the flue gases due to combustion processes, have been undertaken.8−11 However, limited information is available for many of the components that would be present in the flue gas. In particular, © XXXX American Chemical Society
2. EXPERIMENTAL SECTION 2.1. Materials. Perfluoro-n-octane (C8F18; CAS Number: 307-34-6) was supplied by Apollo Scientific (England) with a certified purity of at least 99% by mass. Oxygen (O2, CAS Number: 7782-44-7), nitrogen (N2, CAS Number: 7727-37-9), and methane (CH4, CAS Number: 74-82-8) were supplied by Received: July 18, 2017 Accepted: October 13, 2017
A
DOI: 10.1021/acs.jced.7b00657 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
Journal of Chemical & Engineering Data
Article
Table 1. Pure-Component PC-SAFT Model Parameters and Properties for Oxygen, Nitrogen, Methane, and Perfluoro-n-octane oxygen
nitrogen
methane
99.999 100 NA NA
>99.5 >99.8 NA NA
99 >99 ρexp = 1.756; ρlit = 1.757b ηexp = 1.268; ηlit = 1.270c
1.2053e 3.3130e 90.96e
1d 3.7039d 150.03d
5.7003f 3.7128f 183.02f
component characterization supplier purity/vol % 99.5 GC areaa >99.9 liquid density @ 298 K NA refractive index @ 293 K NA PC-SAFT model pure-component parameters m 1.1217d σ/[Å] 3.2098d ε/k/[K] 114.96d
perfluoro-n-octane
a
Area percentage of component identified by gas chromatography using a thermal conductivity detector and a 30 m Rtx-1 RESTEK capillary column. Data for the liquid density (P = 101 kPa) of perfluoro-n-octane from NIST TDE.32 U(T) = 0.05 K; U(ρ) = 0.001 g.cm−3; U(P) = 1 kPa (k = 2). c Data for the refractive index (P = 101 kPa) of perfluoro-n-octane from the literature.33 U(T) = 0.05 K; U(n) = 0.001; U(P) = 1 kPa (k = 2). d PC-SAFT parameters from the literature.18 ePC-SAFT parameters from the literature.20 fRegressed to the literature vapor pressure and density data.1,21−31 b
apparatus has been presented in detail in previous publications and a schematic of the apparatus is displayed in Figure 1.13−16 A schematic of the second apparatus, based on the “staticsynthetic” method, is presented in Figure 2. A 10 cm3 equilibrium cell, that is constructed from a sapphire cylinder enclosed using two stainless steel 316L flanges, was used for the determination of bubble points via variation of the internal cell volume via a hydraulically driven SS 316L piston. The piston is driven by a hydraulic fluid, which is pressurized with a highpressure syringe pump (Teledyne ISCO; 100DM). An internal Teflon stirrer within the equilibrium chamber can be rapidly rotated via an externally driven Neodymium magnet. The temperature of the equilibrium chamber is controlled via conduction from a thermo-regulated liquid solution. The thermo-regulated solution is contained in a 30 dm3 SS 316L bath containing two viewing windows (100 mm OD). The temperature of the solution is controlled via an immersion circulator (Grant; TX 150). The pressure and temperature within the equilibrium chamber are measured using a single pressure transmitter (WIKA; P-10) and two 100 Ω platinum resistance thermometers (Pt100) probes (WIKA; 1/10 DIN), respectively. The signals from these sensors are recorded by a computer linked to a data acquisition unit (Agilent; HP34970A). A two-stage vacuum pump (Edwards; RV3) is used for evacuation of the cell and loading lines. 2.3. Calibrations and Experimental Uncertainty. All Pt100 probes were calibrated against a reference temperature probe (WIKA Instruments; CTH 6500). The pressure transmitters (25 MPa gauge and 12 MPa gauge) were calibrated against a standard 25 MPa gauge pressure transmitter (WIKA; CPT 6000). For the “static-analytic” method the number of moles of gas was correlated to the TCD response by injecting known volumes of the respective components. The response of the TCD for all components was observed to be linear over the entire working range. The expanded uncertainties (U) were estimated following the guidelines supplied by NIST (National Institute of Standards and Technology).17 The standard uncertainties used for the estimation are listed in Table 2. The uncertainties were combined using the law of propagation of uncertainty and expanded by applying a coverage factor of 2. The expanded uncertainties for temperature, pressure and both liquid and vapor phase compositions (on average for all systems), measured via the “static-analytic” method are U(T) = 0.07 K, U(P) = 0.005 MPa, U(xi) = 0.011 and U(yi) = 0.0006, respectively. The expanded uncertainty for temperature, pressure and both liquid compositions (on average for all systems) measured
Figure 1. Schematic of the “static-analytic” apparatus. C: gas cylinder, GC: gas chromatograph, IC: immersion circulator, LP: liquid component vent and load line, OS: overhead stirrer, PP: platinum resistance thermometer probe, PT: pressure transducer, R: ROLSI, SM: stepper motor, TR: temperature regulation, V: vent line, VP: vacuum pump.13,16
Afrox (South Africa) with certified purities of 99.5, 99.999, and >99.5% by volume, respectively. The purity of perfluoro-noctane was previously characterized using density (Anton Paar; DMA 5000; estimated uncertainty of ±0.001 g/cm−3), refractive index (Bellingham & Stanley; Abbe 60LR; estimated uncertainty of ±0.001), and vapor pressure measurements, as well as by gas chromatography. The light gases, namely, oxygen, nitrogen, and methane were characterized by gas chromatography. Table 1 provides pure-component parameters and properties for the chemicals used in this work. 2.2. Apparatuses Tense. The data were measured using two apparatuses, one following the “static-analytic” method the other following the “static-synthetic” method. The first B
DOI: 10.1021/acs.jced.7b00657 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
Journal of Chemical & Engineering Data
Article
Figure 2. Schematic of the “static-synthetic” apparatus incorporating a variable-volume sapphire cell. IC: immersion circulator, LB: liquid bath, LP: loading port, PP: platinum resistance temperature probe, PT: pressure transducer, SM: stirrer motor, SP: syringe pump, TR: temperature regulation.
change in pressure, and equilibrium was reached); at this point the mixer was then stopped. The capillary tube of the ROLSI was then positioned within either the liquid or vapor phase and samples for each phase (at least six consistent samples) were withdrawn and analyzed via the GC (gas chromatograph). The composition of each phase was determined from the TCD (thermal conductivity detector) peak areas and calibrated GC detector response ratios. Pressure and temperature values were recorded and averaged during sampling. To trace the entire phase envelope, the concentration of the lighter component (oxygen, nitrogen, or methane) was increased and equilibrium was re-established, and the T, P, x1, and y1 values were measured by the aforementioned procedure. 2.4.2. “Static-Synthetic” Method. The equilibrium cell was evacuated, and the mass of the apparatus recorded using a mass balance (Ohaus Explorer; maximum capacity of 6100 g; readability of 0.01 g). To reduce the risk of leakage under vacuum, a small amount (∼0.02 g) of the gaseous component was added to the cell to pressurize the vessel. The mass of the apparatus was again recorded to determine the amount of gas loaded. Prior to loading, the liquid component was degassed via periodic vapor withdrawal. It was thereafter loaded into the cell under pressure via a syringe. The loading valve of the equilibrium cell was dried to remove any residual liquid, and the mass of the apparatus was recorded to determine the amount of the liquid component added. The gaseous component was subsequently charged into the equilibrium cell and its mass was determined. The equilibrium cell was then submerged into the temperature-regulated bath fluid and the liquid phase was thoroughly mixed at a pressure slightly below the bubble point pressure. The two-phase binary mixture was then slowly compressed (at a rate of approximately ∼5 to 10 μL/min) under rapid mixing to obtain the bubble-point. The bubble point was obtained by a visual method. The bubble-point pressure was noted upon disappearance of the gaseous phase within the equilibrium cell. This visual observation of the bubble point pressure was repeated multiple times to ensure that an accurate bubble point pressure was recorded. Good mixing and
Table 2. Standard Uncertainty Estimates and Influences for the Variables of this Work source of uncertainty
estimatea
distribution
pressure (P) P reference/MPa: CPT 6000 correlation for P/MPa (25 MPag) correlation for P/MPa (12 MPag) correlation for P/kPa (100 kPa) temperature (T) T reference/K: CTH 6500 correlation for T/K composition (xi .yi) correlation for ni of oxygen correlation for ni of nitrogen correlation for ni of methane correlation for ni of perfluoro-n-octane V of injected gas/liquid from syringeb T of injected gas from syringeb (K) P of injected gas from syringeb (kPa) liquid density of perfluoro-n-octane repeatability (average) of xi repeatability (average) of yi [O2 and N2 systems] repeatability (average) of yi [methane system] mass balance uncertainty (g)
0.025% 0.020 0.010 0.025
normal rectangular rectangular rectangular
0.03 0.05
rectangular rectangular
1.5% 3.0% 2.5% 1.8% 2% 2 1 1.5% σ̅x = 0.001 σ̅y = 0.0001
rectangular rectangular rectangular rectangular rectangular rectangular rectangular rectangular rectangular rectangular
σ̅y = 0.0005 0.03
rectangular rectangular
a
Estimate treated as either a type A or type B distribution (refer to NIST guidelines).17 bUncertainties inherent to the direct injection method, estimated from the ideal gas law.
via the “static-synthetic” method are U(T) = 0.06 K, U(P) = 0.01 MPa, and U(xi) = 0.007, respectively. 2.4. Experimental Procedure. 2.4.1. “Static-Analytic” Method. The liquid component, perfluorooctane was loaded into the equilibrium cell and degassed. At a predefined temperature, a binary mixture was then prepared within the cell by introducing the lighter component (oxygen, nitrogen, or methane). At constant temperature, the binary mixture was rapidly agitated until the pressure stabilized to a constant average value (note at this point there was no observable C
DOI: 10.1021/acs.jced.7b00657 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
Journal of Chemical & Engineering Data
Article
Figure 3. (a) Deviations between the vapor pressure reported in literature and the data modeled by the PC-SAFT EOS for perfluorooctane at temperatures of between T = 288.1 and 508.3 K. (b) Deviations between the liquid density reported in literature and the data predicted by the PC-SAFT EOS for perfluorooctane at temperatures of between 275.2 and 502.3 K.
Table 3. T-P-x-y Data for the System of N2 (1) and Perfluorooctane (2) at Temperatures between 293.21 and 333.21 K, Measured with a Static-Analytic Apparatus, Including the Estimated Expanded Uncertainties in Temperature (T), Pressure (P), and Composition (x1 and y1), Calculated with a Coverage Factor, k, of 2a T/K
P/MPa
x1
y1
U(x1)
U(y1)
293.21 293.20 293.21 293.21 293.21 293.21 293.22 293.21 293.22 293.22 293.21 293.21 293.21 303.21 303.21 303.21 303.21 303.21 303.22 303.22 303.20 303.20 303.20 303.22 303.23 303.21 303.22 333.20 333.22 333.21 333.21 333.20 333.22 333.21 333.19 333.23 333.19
1.789 3.659 5.699 7.042 8.716 10.054 10.924 11.893 13.074 14.186 15.098 16.445 17.515 2.394 3.577 5.850 6.401 7.366 8.523 9.919 11.193 12.638 13.568 14.242 15.436 16.314 17.601 2.038 3.101 4.317 4.355 5.401 6.395 7.479 8.277 9.451 10.898
0.069 0.128 0.190 0.232 0.274 0.305 0.329 0.349 0.373 0.396 0.413 0.437 0.456 0.089 0.129 0.195 0.214 0.239 0.271 0.306 0.334 0.366 0.384 0.399 0.422 0.439 0.464 0.077 0.114 0.154 0.156 0.189 0.218 0.248 0.269 0.299 0.336
0.9966 0.9975 0.9981 0.9981 0.9979 0.9976 0.9974 0.9973 0.9970 0.9968 0.9965 0.9960 0.9955 0.9960 0.9967 0.9974 0.9973 0.9973 0.9972 0.9969 0.9963 0.9957 0.9955 0.9950 0.9943 0.9939 0.9934 0.9865 0.9896 0.9913 0.9914 0.9920 0.9922 0.9924 0.9925 0.9924 0.9922
0.004 0.006 0.009 0.010 0.011 0.012 0.013 0.013 0.013 0.014 0.014 0.014 0.014 0.005 0.006 0.009 0.010 0.010 0.011 0.012 0.013 0.013 0.013 0.014 0.014 0.014 0.014 0.004 0.006 0.007 0.008 0.009 0.010 0.011 0.011 0.012 0.013
0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0003 0.0003 0.0003 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0003 0.0003 0.0003 0.0003 0.0004 0.0004 0.0008 0.0006 0.0005 0.0005 0.0005 0.0005 0.0004 0.0004 0.0004 0.0005
Table 3. continued
a
T/K
P/MPa
x1
y1
U(x1)
U(y1)
333.18 333.21
13.068 15.112
0.384 0.424
0.9912 0.9905
0.013 0.014
0.0005 0.0005
U(T) = 0.07 K; U(P) = 0.005 MPa.
slow compression speeds are necessary for reliable bubble-point pressures.
3. DATA TREATMENT The data were regressed using the PC-SAFT EOS, developed by Gross and Sandowski.18,19 This model assumes that the nonspherical molecules are chains of hard spherical segments. This simple assumption allows for the model to account for the sizes and shapes of the molecules, and can therefore be used to model mixtures containing vastly different sized molecules. The PC-SAFT EOS is therefore particularly suited to systems with long-chained fluorinated alkanes, such as perfluorooctane, in binary systems with light gases, such as N2, O2, and CH4, as is reported in this study. For the PC-SAFT EOS, three pure-component parameters must be obtained for each component. Many of these pure-component parameters have been reported in literature. However, if no pure-component parameters are available, these must be regressed using properties, such as liquid density, vapor pressure, and liquid heat capacity of the pure-component. The PC-SAFT model was regressed to the experimental data using Aspen Plus V8.8. For the pure-component parameters, the ordinary least-squares objective function was minimized using the Britt-Luecke algorithm. For the regression of the binary parameter for each system, the modified Barker’s objective function (ω), which accounted for the deviations in the vapor phase composition and the pressure, was minimized using the Britt-Luecke algorithm. i ⎡ (y − y m )2 ⎤ (P − P m)2 ω = ∑⎢ i 2 i + i 2i ⎥ ⎢ ⎥⎦ σP , i σy , i Np ⎣ (1) Where Np is the number of data points, the subscript m denotes the modeled values, and σ denotes the standard deviation. Various initial values were used in the search for the global minimum of the objective function. D
DOI: 10.1021/acs.jced.7b00657 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
Journal of Chemical & Engineering Data
Article
Table 4. T-P-x-y Data for the System of O2 (1) and Perfluorooctane (2) at Temperatures between 293.25 and 333.23 K, Measured with a Static-Analytic Apparatus, Including the Estimated Expanded Uncertainties in Temperature (T), Pressure (P), and Composition (x1 and y1), Calculated with a Coverage Factor, k, of 2a
a
Table 5. T-P-x-y Data for the System of Methane (1) and Perfluorooctane (2) at Temperatures between 293.24 and 353.22 K, Measured with a Static-Analytic Apparatus, Including the Estimated Expanded Uncertainties in Temperature (T), Pressure (P), and Composition (x1 and y1), Calculated with a Coverage Factor, k, of 2a
T/K
P/MPa
x1
y1
U(x1)
U(y1)
T/K
P/MPa
x1
y1
U(x1)
U(y1)
293.26 293.25 293.26 293.25 293.23 293.22 293.21 293.26 293.21 293.26 293.26 293.25 293.25 293.26 293.27 293.28 293.28 313.23 313.23 313.22 313.22 313.22 313.22 313.22 313.22 313.22 313.22 313.22 313.22 313.22 313.23 313.22 333.25 333.25 333.23 333.24 333.23 333.24 333.23 333.22 333.23 333.23 333.24 333.20 333.21 333.24 333.24
2.249 3.260 4.360 5.425 6.533 7.525 8.714 10.295 12.258 13.390 14.607 15.642 16.588 17.678 18.594 19.694 20.632 2.118 3.691 4.481 6.126 7.412 9.049 10.603 11.944 13.767 15.058 16.616 17.681 18.636 19.501 20.316 1.564 3.061 5.167 6.473 8.188 9.816 11.105 13.027 14.677 16.202 17.313 18.557 19.668 20.799 21.803
0.117 0.165 0.212 0.253 0.293 0.326 0.363 0.408 0.460 0.486 0.514 0.536 0.556 0.579 0.595 0.615 0.631 0.108 0.176 0.209 0.270 0.314 0.364 0.408 0.443 0.487 0.516 0.549 0.571 0.590 0.606 0.620 0.074 0.144 0.226 0.273 0.329 0.377 0.412 0.462 0.500 0.534 0.557 0.582 0.604 0.625 0.645
0.9982 0.9985 0.9983 0.9980 0.9979 0.9976 0.9975 0.9973 0.9975 0.9969 0.9965 0.9961 0.9954 0.9952 0.9946 0.9939 0.9930 0.9929 0.9946 0.9946 0.9948 0.9950 0.9949 0.9948 0.9947 0.9942 0.9929 0.9926 0.9918 0.9911 0.9902 0.9894 0.9810 0.9893 0.9912 0.9912 0.9915 0.9913 0.9909 0.9894 0.9888 0.9880 0.9869 0.9856 0.9842 0.9824 0.9808
0.005 0.007 0.008 0.009 0.010 0.011 0.011 0.012 0.012 0.012 0.012 0.012 0.012 0.012 0.012 0.011 0.011 0.005 0.007 0.008 0.010 0.010 0.011 0.012 0.012 0.012 0.012 0.012 0.012 0.012 0.011 0.011 0.003 0.006 0.008 0.010 0.011 0.011 0.012 0.012 0.012 0.012 0.012 0.012 0.012 0.011 0.011
0.0001 0.0001 0.0001 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0003 0.0003 0.0003 0.0004 0.0004 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0004 0.0004 0.0004 0.0004 0.0005 0.0005 0.0009 0.0005 0.0004 0.0004 0.0004 0.0004 0.0004 0.0005 0.0005 0.0006 0.0006 0.0007 0.0008 0.0008 0.0009
293.23 293.24 293.25 293.25 293.26 293.26 293.25 293.22 293.22 293.21 293.22 323.20 323.21 323.20 323.20 323.21 323.21 323.21 323.21 323.22 323.21 323.22 353.22 353.20 353.22 353.23 353.22 353.24 353.23 353.21 353.22 353.22 353.22 353.23
1.849 3.897 5.724 7.505 9.752 11.913 13.367 15.773 17.749 19.887 20.527 2.364 4.639 6.134 8.270 10.520 12.442 14.258 15.147 16.083 17.114 18.143 1.183 3.572 4.663 6.075 7.645 9.073 11.002 12.020 13.696 14.867 15.380 16.763
0.109 0.215 0.297 0.369 0.451 0.522 0.567 0.637 0.693 0.758 0.781 0.128 0.234 0.298 0.379 0.458 0.520 0.576 0.603 0.631 0.662 0.694 0.060 0.179 0.228 0.287 0.348 0.402 0.469 0.503 0.558 0.595 0.612 0.658
0.9961 0.9966 0.9973 0.9969 0.9949 0.9927 0.9901 0.9841 0.9731 0.9648 0.9556 0.9858 0.9908 0.9910 0.9900 0.9873 0.9846 0.9798 0.9768 0.9731 0.9654 0.9554 0.9500 0.9755 0.9794 0.9792 0.9780 0.9768 0.9743 0.9719 0.9666 0.9615 0.9586 0.9492
0.005 0.009 0.011 0.012 0.013 0.013 0.013 0.012 0.011 0.010 0.009 0.006 0.010 0.011 0.013 0.013 0.013 0.013 0.013 0.012 0.012 0.011 0.003 0.008 0.009 0.011 0.012 0.013 0.013 0.013 0.013 0.013 0.013 0.012
0.0002 0.0002 0.0002 0.0002 0.0004 0.0007 0.0008 0.0010 0.0015 0.0019 0.0023 0.0009 0.0008 0.0007 0.0008 0.0009 0.0010 0.0012 0.0013 0.0015 0.0019 0.0023 0.0026 0.0014 0.0012 0.0012 0.0013 0.0013 0.0015 0.0016 0.0018 0.0021 0.0022 0.0026
a
U(T) = 0.07 K; U(P) = 0.005 MPa.
Table 6. T-P-x Data for Binary Systems of (N2, O2, or Methane) (1) and Perfluorooctane (2) at Temperatures between 293.16 and 353.19 K, Measured with a StaticSynthetic Apparatus, Including the Estimated Expanded Uncertainties in Temperature (T), Pressure (P), and Composition (x1), Calculated with a Coverage Factor, k, of 2a T/K
P/MPa
O2 (1) + perfluorooctane (2) 293.29 7.98 313.19 8.00 333.24 8.24 N2 (1) + perfluorooctane (2) 293.16 6.77 303.19 6.58 333.14 6.41 methane (1) + perfluorooctane (2) 293.26 5.73 323.16 6.02 353.19 6.10
U(T) = 0.07 K; U(P) = 0.005 MPa.
4. RESULTS AND DISCUSSION Pure-component parameters for the PC-SAFT EOS for N2, O2 and methane were obtained from literature.18,20 The parameters for pure perfluorooctane were regressed to single component vapor pressure and liquid density data that was available in the literature.1,21−31 The pure-component PC-SAFT model
a
E
x1
U(x1)
0.338 0.338 0.338
0.003 0.003 0.003
0.221 0.221 0.221
0.007 0.007 0.007
0.29 0.29 0.29
0.010 0.010 0.010
U(T) = 0.06 K; U(P) = 0.01 MPa. DOI: 10.1021/acs.jced.7b00657 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
Journal of Chemical & Engineering Data
Article
Figure 4. P-x-y data for the system of N2 (1) + perfluorooctane (2) at temperatures of between 293.21 and 333.21 K, measured using a static-analytic apparatus at temperatures of, ○, T = 293.21 K; ×, T = 303.21 K; Δ, T = 333.21 K. The PC-SAFT EOS is described by solid lines, ―.
Figure 5. P-x data for the system of N2 (1) + perfluorooctane (2) at temperatures of between 293.21 and 333.21 K, measured using a static-analytic apparatus at temperatures of, ○, T = 293.21 K; ×, T = 303.21 K; Δ, T = 333.21 K. P-x data measured using a static-synthetic apparatus at temperatures of, ●, T = 293.16 K; ×, T = 303.19 K; ▲, T = 333.14 K. The PC-SAFT EOS is described by solid lines, ―.
Figure 6. P-y data for the system of N2 (1) + perfluorooctane (2) at temperatures between 293.21 and 333.21 K, measured using a static-analytic apparatus at temperatures of, ○, T = 293.21 K; ×, T = 303.21 K; Δ, T = 333.21 K. The PC-SAFT EOS is described by solid lines, ―.
parameters are given in Table 1. The ability of the PC-SAFT model, using the regressed parameters, to predict the vapor pressures and densities of perfluorooctane can be observed in the deviations plots for vapor pressure (Figure 3a) and liquid density (Figure 3b). The experimental vapor−liquid equilibrium (P-x-y) data for three binary systems, N2 + perfluorooctane, O2 + perfluorooctane, and methane + perfluorooctane, are presented in Tables 3, 4, and 5. Bubble pressure data for the three systems, measured with a static-synthetic, variable volume apparatus are presented in Table 6. These data were measured to validate the data measured using the static-analytic apparatus. The regressed parameters and the regression statistics for the three systems are given in Table 6. In Figure 4, the plot of the entire P-x-y spectrum that was measured for nitrogen and perfluorooctane is given. These data
are reported in Table 3. Further details of the bubble curve at nitrogen molar compositions between (0 and 0.5) can be seen in Figure 5, while Figure 6 gives an expanded view of the dew point curve at nitrogen molar compositions between (0.98 and 1). The data measured with the static-synthetic apparatus agrees well with the data measured with the staticanalytic apparatus. The prediction of the VLE data by the PC-SAFT EOS, based on the regressed binary parameter, can be seen on these three plots, with good agreement between the experimental data and the model. The ability of the model to predict accurate phase equilibrium is further substantiated by the regression statistics (the MRD and AARD values) provided alongside the regressed parameter in Table 7. The MRDs and AARDs in pressure and composition for the modeling of all three isotherms for this system were less than 1%. The pressure limitations of the F
DOI: 10.1021/acs.jced.7b00657 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
Journal of Chemical & Engineering Data
Article
Table 7. Temperature Dependent PC-SAFT Binary Parameters for the Systems of (N2, O2, or Methane) with Perfluorooctane and the Associated Regression Statistics T range/K
k
O2 (1) + perfluorooctane (2) 293.25−333.23 0.0742 N2 (1) + perfluorooctane (2) 293.21−333.21 0.0488 CH4 (1) + perfluorooctane (2) 293.24−353.22 0.0764
MRD (P)/%
MRD (y)/%
AARD (P)/%
AARD (y)/%
0.26
0.09
1.67
0.13
0.10
0.05
0.84
0.06
1.88
0.15
6.62
0.22
Figure 7. P-x-y data for the system of O2 (1) + perfluorooctane (2) at temperatures between 293.25 and 333.25 K, measured using a static-analytic apparatus at temperatures of, ○, T = 293.25 K; ×, T = 313.22 K; Δ, T = 333.22 K. The PC-SAFT EOS is described by solid lines, ―.
Figure 8. P-x data for the system of O2 (1) + perfluorooctane (2) at temperatures between 293.25 and 333.23 K, measured using a staticanalytic apparatus at temperatures of ○, T = 293.25 K; ×, T = 313.22 K; Δ, T = 333.23 K. P-x data measured using a static-synthetic apparatus at temperatures of, ●, T = 293.29 K; ×, T = 313.19 K; ▲, T = 333.24 K. The PC-SAFT EOS is described by solid lines, ―.
Figure 9. P-y data for the system of O2 (1) + perfluorooctane (2) at temperatures between 293.25 and 333.23 K, measured using a staticanalytic apparatus at temperatures of, ○, T = 293.25 K; ×, T = 313.22 K; Δ, T = 333.23 K. The PC-SAFT EOS is described by solid lines, ―.
experimental apparatus meant that only half of the composition range could be investigated, and it is therefore not possible to comment on the behavior of the model nearer to the critical locus curve of the system. Observations on the performance of the PC-SAFT EOS near to the critical region are therefore also not possible.
The P-x-y plot for the oxygen + perfluorooctane system is given in Figure 7, with an enlarged plot of the bubble and dew point curves given in Figures 8 and 9, respectively. The data that were measured with the static-synthetic apparatus show good agreement with the VLE data that were measured with the static-analytic apparatus. The PC-SAFT model can also G
DOI: 10.1021/acs.jced.7b00657 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
Journal of Chemical & Engineering Data
Article
Figure 10. P-x-y data for the system of methane (1) + perfluorooctane (2) at temperatures between 293.24 and 353.22 K, measured using a staticanalytic apparatus at temperatures ○, T = 293.24 K; ×, T = 323.21 K; Δ, T = 353.22 K. P-x data measured using a static-synthetic apparatus at temperatures of ●, T = 293.26 K; ×, T = 323.16 K; ▲, T = 353.19 K The PC-SAFT EOS is described by solid lines, ―.
“static-synthetic” methods. VLE data were measured for the binary systems of nitrogen + perfluorooctane, oxygen + perfluorooctane, and methane + perfluorooctane within the temperature range of 293.21 to 353.23 K. Within this temperature range, the solubility of the light gases (oxygen, nitrogen and methane) in perfluorooctane is a weak function of temperature. The experimental data were correlated using the perturbed-chain statistical associating fluid theory equation of state. The model provided a satisfactory fit of the experimental data.
describe the bubble curve and the dew curve of the perfluorooctane + O2 system well, with the deviations between the experimental composition and the composition predicted by model prediction in the same order of magnitude as the vapor phase composition uncertainties. The MRDs and AARDs from the modeling of all three isotherms are less than 2%. Again with this system, there is a large composition range for which no data could be measured, due to the high-pressures that would have to be achieved. The solubility of the O2 in the perfluorooctane is not sensitive to temperature differences at lower pressures, with negligible difference in the bubble pressure between 293.21 and 333.25 K. The equilibrium phase data for the methane (1) + perfluorooctane (2) system is plotted in Figure 10. The data that were measured with the static-synthetic apparatus again agree with the data from the static-analytic apparatus. For this system, there was little effect of temperature on the bubble pressure, with very little deviation between the bubble pressures at different temperatures at a given composition. The ability of the PC-SAFT model to predict the phase behavior of this system exhibited some discrepancy as compared to the previous two systems, particularly at compositions 0.2 and 0.6. However, despite the difference in the correlation between the PC-SAFT model and the experimental data being greater than for the other two systems, that is not to say that the model is incapable of predicting the phase behavior of this system. The maximum deviation between the model and the experimental data was 0.8 MPa at a liquid phase composition of methane of 0.4. The MRDs and AARDs for composition for the modeling of all three isotherms are small, at less than 1%, but for the pressure, they are fairly substantial, at 1.9 and 6.6%, respectively. This departure is observed in Figure 10, with the vapor phase being well described by the model, but the bubble curve deviating a fair amount.
■
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jced.7b00657. A note on consistency tests for high-pressure phase equilibrium data (PDF)
■
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Mark Williams-Wynn: 0000-0002-9751-5419 Wayne Michael Nelson: 0000-0003-0544-6530 Deresh Ramjugernath: 0000-0003-3447-7846 Notes
The authors declare no competing financial interest. Funding
This work is based upon research supported by the National Research Foundation of South Africa under the South African Research Chair Initiative of the Department of Science and Technology. The research was also supported by Joint Research Grant under the SA/Algeria (NRF/DGRSDT) Agreement on Cooperation in Science and Technology “Measurement of Thermodynamic and Thermophysical Data for Fluorinated
5. CONCLUSIONS Isothermal VLE data measurements were performed using two different experimental techniques, viz. the “static-analytic” and H
DOI: 10.1021/acs.jced.7b00657 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
Journal of Chemical & Engineering Data
Article
(19) Gross, J.; Sadowski, G. Modeling Polymer Systems Using the Perturbed-Chain Statistical Associating Fluid Theory Equation of State. Ind. Eng. Chem. Res. 2002, 41, 1084−1093. (20) Tihic, A.; Kontogeorgis, G. M.; von Solms, N.; Michelsen, M. L. Applications of the simplified perturbed-chain SAFT equation of state using an extended parameter table. Fluid Phase Equilib. 2006, 248, 29− 43. (21) Kreglewski, A.; Fajans, A. Thermodynamic excess functions of binary mixtures of trifluoroacetic acid with tris(perfluoro-n-butyl)amine and perfluoro-n-octane. Bull. Acad. Polym. Sci.-Chim. 1965, 13, 441−446. (22) Kreglewski, A. Solubility of gaseous trifluoroacetonitrile in certain solvents. Bull. Acad. Polym. Sci.-Chim. 1965, 13, 729−734. (23) Ermakov, G. V.; Skripov, V. P. Saturation Line, Critical Parameters, and Attainable Superheating of the Perfluoroparaffins. Russ. J. Phys. Chem. 1967, 41, 39−43. (24) Varushchenko, R. M.; Bulgakova, L. L.; Mirzabekyanc, P. S.; Makarov, K. N. Saturated Vapor Pressures and Vaporization Enthalpies of Some Perfluorocarbons. Zh. Fiz. Khim. 1981, 55, 2624−2628. (25) Mustafaev, M. R.; Naziev, Y. M.; Kagramanov, M. K. The density of some perfluorocarbons in a wide range of state parameters. High Temp. (Engl. Transl.) 1995, 33, 359−366. (26) Mustafaev, M. R.; Imanov, A. S.; Kurbanova, S. K. Instrument for the Determination of the Vapor Pressure, Critical Temperature, and Critical Pressure of Perfluorocarbons. High Temp. (Engl. Transl.) 1996, 34, 303−307. (27) Tochigi, K.; Satou, T.; Kurihara, K.; Yamamoto, H.; Mochizuki, Y.; Ochi, K.; Sako, T. J. Vapor-Liquid Equilibrium Data for the Four Binary Systems Containing Fluorocarbon, Hydrofluorocarbon, and Fluorinated Ethers at 101.3 kPa. J. Chem. Eng. Data 2001, 46, 913− 917. (28) Vandana, V.; Rosenthal, D. J.; Teja, A. S. The critical properties of perfluoro n-alkanes. Fluid Phase Equilib. 1994, 99, 209−218. (29) Deschamps, J.; Menz, D.-H.; Padua, A. A. H.; Gomes, M. F. C. Low pressure solubility and thermodynamics of solvation of oxygen, carbon dioxide, and carbon monoxide in fluorinated liquids. J. Chem. Thermodyn. 2007, 39, 847−854. (30) Hallewell, G.; Vacek, V.; Vins, V. Properties of saturated fluorocarbons: Experimental data and modeling using perturbed-chainSAFT. Fluid Phase Equilib. 2010, 292, 64−70. (31) Kennan, R. P.; Pollack, G. L. Solubility of xenon in perfluoroalkanes: Temperature dependence and thermodynamics. J. Chem. Phys. 1988, 89, 517−521. (32) Frenkel, M.; Chirico, R. D.; Diky, V.; Yan, X.; Dong, Q.; Muzny, C. NIST ThermoData Engine 6.0. National Institute of Standards and Technology; NIST Applied Chemicals and Materials Division: Thermodynamics Research Center (TRC), 2005. (33) Williamson, T. H. Vitreoretinal Surgery; Springer: Berlin, 2007; Vol. 8.
Organics and Petrochemicals”. One of the authors (Z. Tebbal) acknowledges a grant from the Algerian Ministry of High Education and Scientific Research (MESRS).
■
REFERENCES
(1) Dias, A. M. A.; Caco, A. I.; Coutinho, J. A. P.; Santos, L.M.N.B.F.; Pineiro, M. M.; Vega, L. F.; Costa Gomes, M. F.; Marrucho, I. M. Thermodynamic properties of perfluoro-n-octane. Fluid Phase Equilib. 2004, 225, 39−47. (2) Ostheim, S. Opportunities for Innovation: Pollution Prevention; Technomic Publishing Co. Inc: U.S.A, 1995. (3) Lam, P.; Loganathan, B. G Global Contamination Trends of Persistent Organic Chemicals; CRC Press: U.S.A, 2011. (4) Riess, J. G. Oxygen Carriers (“Blood Substitutes”) - Raison d’Etre, Chemistry, and Some Physiology. Chem. Rev. 2001, 101, 2797− 2919. (5) Lemal, D. M. Perspective on Fluorocarbon Chemistry. J. Org. Chem. 2004, 69, 1−11. (6) Abraham, M. H.; Acree, W. E.; Matteoli, E. The factors that influence solubility in perfluoroalkane solvents. Fluid Phase Equilib. 2016, 421, 59−66. (7) Mangena, M. Fluorochemical Expansion Initiative Launch; Department of Science and Technology: Pretoria, South Africa, 2009. (8) Tshibangu, M. M.; Valtz, A.; Narasigadu, C.; Coquelet, C.; Ramjugernath, D. Vapor-liquid Equilibrium (VLE) Data and Thermodynamic Modelling for Binary Systems Containing Perfluorobutane (R610) with Carbon Monoxide or Nitric Oxide at (293, 313, and 333) K. J. Chem. Eng. Data 2014, 59, 346−354. (9) Tshibangu, M. M.; Valtz, A.; Narasigadu, C.; Coquelet, C.; Ramjugernath, D. Isothermal Vapor-Liquid Equilibrium (VLE) Data and Thermodynamic Modelling for Binary Systems of Perfluorobutane (R610) + (Methane or Hydrogen Sulphide) at (293, 313 and 333) K. J. Chem. Eng. Data 2014, 59, 2865−2871. (10) Tshibangu, M. M.; Valtz, A.; Narasigadu, C.; Coquelet, C.; Ramjugernath, D. Isothermal Vapor-Liquid Equilibrium (VLE) and Vapor-Liquid-Liquid Equilibrium (VLLE) Data for Two Binary Systems Containing Perfluorohexane with Carbon Monoxide or Hydrogen Sulphide at (293, 313 and 333) K. J. Chem. Eng. Data 2015, 60, 2461−2468. (11) Dias, A. M. A.; Pàmies, J. C.; Coutinho, J. A. P.; Marrucho, I. M.; Vega, L. F. SAFT Modeling of the Solubility of Gases in Perfluoroalkanes. J. Phys. Chem. B 2004, 108, 1450−1457. (12) Nelson, W. M.; Tebbal, Z.; Naidoo, P.; Negadi, L.; Ramjugernath, D. High-pressure phase equilibria data for mixtures involving ethene and perfluoro-n-octane from 293 to 353 K. Fluid Phase Equilib. 2016, 408, 33−37. (13) Tebbal, Z.; Nelson, W. M.; Naidoo, P.; Negadi, L.; Ramjugernath, D. Binary vapour-liquid equilibrium data for C7 and C9 straight-chain perfluorocarbons with ethylene. Fluid Phase Equilib. 2016, 429, 37−44. (14) Nelson, W. M.; Naidoo, P.; Ramjugernath, D. Phase equilibrium data for potentially hazardous binary mixtures involving dichlorosilane, trichlorosilane and silicon-tetrachloride. J. Chem. Thermodyn. 2015, 91, 420−426. (15) 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. (16) Nelson, W. M.; Tebbal, Z.; Naidoo, P.; Negadi, L.; Ramjugernath, D. High-pressure phase equilibria data for mixtures involving ethene and perfluoro-n-octane from 293 to 353 K. Fluid Phase Equilib. 2016, 408, 33−37. (17) Taylor, B.N.; Kuyatt, C.E. NIST Technical Note 1297: Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results; National Institute of Standards and Technology: Gaithersburg, 1994. (18) Gross, J.; Sadowski, G. Perturbed-Chain SAFT: An Equation of State Based on a Perturbation Theory for Chain Molecules. Ind. Eng. Chem. Res. 2001, 40, 1244−1260. I
DOI: 10.1021/acs.jced.7b00657 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
