VaporâLiquid Equilibrium Measurements for Carbon Dioxide +

Article pubs.acs.org/jced

Vapor−Liquid Equilibrium Measurements for Carbon Dioxide + Cyclohexene + Squalane at High Pressures Using a Synthetic Method Fedra A. V. Ferreira,* Thales Caina ̃ dos Santos Barbalho, Humberto Neves Maia de Oliveira, and Osvaldo Chiavone-Filho Department of Chemical Engineering, Universidade Federal do Rio Grande do Norte, Natal, Rio Grande do Norte (RN), 59078-970 Brazil ABSTRACT: Growing interest in the study of production conditions in the presalt led to the need to study complex systems at high pressures and temperatures, such as up to 70 MPa and up to 393 K. The aim of this work is to obtain vapor−liquid equilibrium data at high pressures and temperatures for hydrocarbon systems with carbon dioxide (CO2). To obtain these data, an experimental setup and procedure using a synthetic cell were designed. Experimental data of the binary system CO2 + cyclohexene (C6H10) and CO2 + squalane (C30H62) over a range of temperature between 303 and 398 K and the ternary system CO2 + C6H10 + C30H62 at various temperatures (318−393 K) and compositions are reported. It is noteworthy that the reported measurements in this work were not studied in the literature, and experimental data may contribute to industrial and scientific interests. The phase behavior of the system was also described using the Soave−Redlich−Kwong equation of state together with Mathias− Copeman alpha function. Interaction parameters for the attractive and repulsive terms were estimated in order to describe the experimental data within the estimated uncertainties.

1. INTRODUCTION A knowledge of phase equilibrium at high pressures is very important for the understanding of the technique and the natural processes that occur at high pressures. It is essential for the design, chemical process, optimization, and separation processes at high pressure. Phase equilibrium at high pressures is very important in the oil industry; some examples of this contribution are reservoir oil PVT behavior simulation, enhanced oil recovery, and the transport and storage of natural gas.1 There are several methods that have been proposed for the experimental determination of high-pressure phase equilibria. Dohrn and contributors have reported an extensive body of reviewed work through the years contemplating most of the work done at high pressure, with all classified methods applied.1−5 The contributions of this work are the new experimental data of a mixture with defined species that intends to represent the oil in the reservoir at corresponding conditions of pressure and temperature. The selected compounds were carbon dioxide, which is present in high percentages in the presalt oil, e.g., up until 20%, cyclohexene, which represents an aromatic fraction of hydrocarbons and squalane, representing the heavy part of hydrocarbons,6 and also a paraffinic one. Phase behavior was studied initially by the bubble-point determination of binary system CO2 + C6H10 in the temperature range between 313 and 398 K, at pressures from 5.55 to 12.41 MPa, and at CO2 composition in the mole fraction range of between 0.299 and 0.850. Binary system CO2 + C30H62 was also studied in the temperature range between © XXXX American Chemical Society

303 and 393 K, at pressures from 5.60 to 19.66 MPa, and at CO2 compositions, in mole fraction range, of between 0.474 and 0.800. Ternary system CO2 + C6H10 + C30H62 was also studied, in the temperature range between 318 and 393 K, at pressures from 3.24 to 12.98 MPa, and at CO2 composition, in mole fraction range, of between 0.233 and 0.641. Two different experimental methods were applied: SynVis and SynNon. The phase behavior was correlated using the Soave−Redlich−Kwong7 (SRK) equation of state (EoS) with a quadratic mixing rule (vdw2) using interaction parameters (kij and lij) and the Mathias−Copeman8 alpha function. This approach was found to be satisfactory for describing the mixtures of interest, and the SRK EoS with vdw2 mixing rule is usually available in phase equilibrium and process simulators. There are no available data in the literature for binary systems CO2 + cyclohexene and cyclohexene + squalane and ternary system CO2 + cyclohexene + squalane. Data found in the literature for system CO2 + squalane are summarized in Table 1.

2. EXPERIMENTAL SECTION 2.1. Materials. All chemicals were obtained from commercial sources and were found to be within acceptable purity specifications and were used without further purification. Received: December 8, 2016 Accepted: March 7, 2017

A

DOI: 10.1021/acs.jced.6b01018 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

of the sample and determining the equilibrium point indirectly as held by noninvasive techniques. In the SynVis method, the expected result is to observe a phase change, and the sample for analysis is not required, which means that the experiment is more practical and safer.5 The liquid mixtures were prepared and used to charge the cell gravimetrically with the aid of an analytical balance (±0.0001 g). For carbon dioxide addition, a syringe pump was used (±0.008 g). Considering losses from the operational processes of transfer and mixture, the uncertainty in the composition is estimated to be 0.005 mole fraction. Phase equilibrium experiments were carried out in a highpressure variable-volume view cell. The experimental apparatus used in this work is similar to the one used in previous investigations.15−18 A schematic diagram of the experimental apparatus is shown in Figure 1. To illustrate the designed experimental setup, Figure 2 is presented. The experimental setup is composed of a variable-volume view cell with a sapphire window for visual observation, an absolute pressure indicator (Gefran, 600 model) with a precision of ±0.01 MPa for pressure data acquisition, and a syringe pump (SCO, model 260D) with a thermostatic bath (Nova Ética 521-4D) for the quantitative addition of CO2 and pressure control. For temperature control, the equilibrium cell contains an aluminum jacket and a temperature controller (Novus N480D) connected to a Pt100 (Novus N480I, accuracy 0.1 K), which was in direct contact with the sample inside the equilibrium cell. A movable piston allows pressure control inside the cell and phase transitions were inferred by manipulating of this parameter while keeping the temperature constant. An amount of cyclohexene and squalane was weighed on a high-accuracy scale (Shimadzu AUW220D, uncertainty 0.0001 g) and loaded into the cell, and CO2 was injected into the system from the syringe pump to achieve the preestablished global composition. Posteriorly, the cell content remained at continuous agitation with the aid of a magnetic stirrer and a Teflon-coated stirring bar. After reaching the desired temperature, the pressure of the cell was increased by applying CO2, as an auxiliary fluid, to the back of the piston with the help of the syringe pump until the system reaches a single-phase state, the liquid state. To provide the phase transition, the pressure of the cell was decreased slowly until the formation of the vapor phase as observed through the sapphire window, so the pressure was recorded.

Table 1. Data Available in the Literature for System CO2 + Squalane no. of exp. points

authors/year

T/K

P/MPa

Mokbel et al./ 19989 Brunner et al./ 200910 Liphard et al./ 197511 Chai et al./ 198112 Sovova et al./ 199713

400−860

8.6 × 10−7−0.86

1

7

313.5− 426 280.3− 421.85 298.59− 330.18 303.2− 328.5

3.5−35

0.116− 0.878 0.0077− 0.5803

33

1.6−100

xC30H62

177 11

7.910−27.500

34

Table 2 presents information about the compounds used in this work. Table 2. Sources and Corresponding Purities of the Pure Species Studied chemical name

source

mole fraction purity

carbon dioxide, CO2 cyclohexene, C6H10 ethanol, C2H6O squalane, C30H62

Linde Sigma-Aldrich Merck Sigma-Aldrich

0.99 0.99 0.998 0.99

In Table 3, some properties of the substances used are listed. Table 3. Critical Properties and Molar Mass of the Substances Studieda compound

Tc/K

Pc/MPa

MM/g mol−1

carbon dioxide, CO2 cyclohexene, C6H10 ethanol, C2H6O squalane, C30H62

304.21 560.40 513.92 844.00

7.383 4.35 6.07 0.80

44.01 82.145 46.069 422.822

a

[DIPPR];14 Tc, critical temperature; Pc, critical pressure; MM, molecular mass.

2.2. Apparatus and Procedure. The synthetic static method was used to obtain the phase equilibria, or transitions, of the studied systems. Its main feature is to perform the experiment in a closed system knowing the initial composition

Figure 1. Scheme of the experimental apparatus. TB, thermostated bath; SP, syringe pump; P, piston; V, valve; FSW, front sapphire window; SSW, side sapphire window; TC, temperature controller; PI, pressure indicator; MS, magnetic stirrer. B



Article

Figure 2. Illustration of the designed experimental apparatus.

The previous procedure was repeated at least five times for each temperature and global composition. After the completion of the measurement at a given temperature, this parameter was set to a new value and the experimental procedure was repeated. To compare the results of the visual method, we also plotted pressure versus volume to check the behavior of the system before and after the onset of the first vapor bubble. Dorhn and his contributors had also used this methodology in work using a high-pressure view cell.19 It was then possible to calculate the pressure at which a phase change to a constant temperature occurs.

3. RESULTS AND DISCUSSION 3.1. System Validation: CO2 + Ethanol. To validate the methodology and experimental apparatus, some vapor−liquid Table 4. Experimental Results for the CO2 (1) + C2H6O (2) System Using the Synthetic-Visual (SynVis) Methoda x1 (mole fraction)

T/K

P/MPa

0.4998 0.4998 0.4998 0.4998 0.4998 0.4998 0.4998 0.4998 0.4998

305.08 313.08 323.00 333.10 343.39 352.97 363.25 372.50 383.49

5.58 6.36 7.42 9.04 10.11 11.14 12.06 12.77 13.47

Figure 3. Phase envelope diagram for experimental data of the CO2 + ethanol system in this work is compared to that of other authors and ́ to the fitted interaction parameters using SRK EoS from Galicia-Luna and collaborators:20 (orange ●) this work; (gray ■) Tsivintzelis;23 20 ́ (yellow ▲) Pfohl;22 (blue ⧫) Galicia-Luna; (green ×) Jennings;21 24 (gray ×) Wu; and (gray −) RK-EoS (kij = 0.0742 and lij = −0.0206).

(Figure 3). For example, the comparison between the measured data and the work of Wu and contributors24 give a maximum deviation of 1.54%, validating the experimental procedure. Furthermore, the deviation between the measured and calculated values from SRK EoS using fitted interaction parameters based on literature data20 resulted in 0.38%. Before performing the experimental work, we carried out computational methodology, applying the Soave−Redlich− Kwong equation of state,7 associated with the Mathias− Copeman8 alpha function and using a quadratic mixing rule (vdw2) considering interaction parameters kij and lij through the SPECS v5.63 simulator to predict the equilibrium phase behavior of the systems studied. This was performed to give an approximated range of the experimental behavior to aid the measurements. 3.2. Binary Systems: CO2 + C6H10 and CO2 + C30H62. Phase equilibrium data obtained for binary CO2 + C6H10 using the SynVis method in the range of 0.2999 mole fraction of CO2

a

Standard uncertainties u are u(x1) = 0.005 mole fraction, u(T) = 0.3 K, and u(P) = 0.1 MPa.

data for the system CO2 + ethanol were obtained. The composition of the system was set to 0.5 mole fraction of CO2. The experiment occurs at nine different temperatures between 305.08 and 383.49 K and at pressures from 5.58 up to 13.47 MPa. This experimental apparatus was already used in previous work.15 There are several works reported in the literature for binary system CO2 + ethanol. The more significant data sets were chosen.20−24 First, the SPECS simulator was used to estimate the interaction parameters for the binary system using SRK 20 ́ EoS. The work of Galicia-Luna and his collaborators was used to estimate mixing rule interaction parameters, resulting in kij = 0.0742 and lij = −0.0206, using a total of 48 experimental points. The experimental results (Table 4) are in good agreement with the measurements available in the literature C



Article

Table 5. Experimental Results for the CO2 (1) + C6H10 (2) System Using the SynVis Methoda x1 (mole fraction)

T/K

P/MPa

x1 (mole fraction)

T/K

P/MPa

0.2999 0.2999 0.2999 0.3978 0.3978 0.3978 0.3978 0.4635 0.4635 0.4635 0.4635 0.5147 0.5147 0.5147 0.5147 0.6001 0.6001 0.6001

371.42 383.30 392.81 328.29 348.21 371.48 388.23 338.92 357.45 375.30 387.20 328.23 348.61 372.20 398.45 313.35 342.37 371.55

6.14 6.67 6.94 5.55 6.72 8.08 9.04 7.15 8.50 9.81 10.63 6.85 8.57 10.62 12.41 6.13 8.95 11.63

0.6501 0.6501 0.6501 0.6998 0.6998 0.6998 0.7490 0.7490 0.7490 0.7671 0.7671 0.7671 0.8001 0.8001 0.8001 0.8504 0.8504 0.8504

313.15 323.25 333.20 313.20 323.25 333.15 313.15 323.15 333.18 313.25 323.20 333.15 313.15 323.15 333.15 313.62 323.22 333.15

6.33 7.36 8.37 6.51 7.62 8.69 6.62 7.74 8.94 6.67 7.84 8.99 6.93 8.23 9.42 7.21 8.47 9.75

Figure 5. P−V diagram for the system CO2 + C6H10 with a mole fraction of CO2 of 0.4635 at four different temperatures: (gray × with |) 338.95 K, (gray ●) 357.45 K, (gray ⧫) 375.15 K, and (gray ×) 387.25 K.

a Standard uncertainties u are u(x1) = 0.005 mole fraction, u(T) = 0.3 K, and u(P) = 0.1 MPa.

Table 7. Experimental Results for the CO2 (1) + C30H62 (2) System Using the SynVis Methoda

Figure 4. P−x−y diagram for the system CO2 + C6H10 at three different temperatures: (gray ●) 313.15 K, (gray ⧫) 323.15 K, (gray ×) 333.15 K, and (gray −) SRK-EoS (kij = 0.1065; lij = −0.0236).

T/K

P/Mpa

0.4635 0.4635 0.4635 0.4635

338.95 357.45 375.15 387.15

6.977 8.587 9.150 10.567

T/K

P/MPa

x1 (mole fraction)

T/K

P/MPa

0.4738 0.4738 0.4738 0.4738 0.4738 0.56221 0.56221 0.56221 0.56221 0.56221 0.56221 0.56221 0.6030 0.6030 0.6030 0.6030 0.6030

353.23 362.59 374.10 382.725 392.97 332.80 342.83 353.27 363.39 373.41 383.47 393.67 322.98 333.48 343.23 352.60 364.11

5.65 6.08 6.60 6.96 7.36 6.18 6.68 7.24 7.93 8.45 8.95 9.42 6.21 7.14 7.68 8.34 8.89

0.6030 0.6030 0.6030 0.6854 0.6854 0.6854 0.6854 0.6854 0.6854 0.8002 0.8002 0.8002 0.8002 0.8002 0.8002 0.8002 0.8002

373.13 382.75 393.48 303.40 313.28 323.20 333.23 343.08 353.33 313.15 323.52 333.13 343.22 353.20 363.05 373.15 383.15

9.42 9.99 10.79 6.18 7.06 8.15 8.99 9.96 10.69 10.33 11.91 13.46 14.60 16.09 17.36 18.52 19.66

a


Table 6. Experimental Results for the CO2 (1) + C6H10 (2) System Using the SynNon Methoda x1 (mole fraction)

x1 (mole fraction)

In Figure 4, the experimental results in the form of a P-x-y diagram for the system CO2 + cyclohexene at 313.15, 323.15, and 333.15 K are presented, using the SynVis method. The vapor−liquid equilibrium data were correlated with the Soave− Redlich−Kwong7 equation of state, with Mathias−Copeman8 parameters and the vdw2 mixing rule. Agreement between our measured with thermodynamic model used was observed within experimental uncertainties, with absolute average deviation in pressure (AAD_P) = 2.1% and maximum absolute deviation in pressure (MD_P) = 4.7%. The SynNon method was also used for a few points for a CO2 mole fraction of 0.4635 and in the temperature range


up to 0.8504 and the range of temperature of 313.15 up to 398.45K are listed in Table 5. D



Article

one describes the equilibrium points of the homogeneous liquid region, and the second one, the heterogeneous phase region. The results are presented in Figure 5 for the mixture at a constant composition at four temperatures. The quantitative agreement between visual and nonvisual methods indicates the feasibility of the technique for the nontranslucent samples. Vapor−liquid equilibrium data obtained for binary CO2 + C30H62 using the SynVis method in the range of 0.4738 mole fraction of CO2 up to 0.8002 and the range of temperature of 303.40 up to 393.67 K are listed in Table 7. In Figure 6, the experimental results in the form of a P−T diagram for system CO2 + squalane at four different compositions are presented using the SynVis method. The vapor−liquid equilibrium data were correlated with the Soave−Redlich−Kwong7 equation of state, with Mathias− Copeman8 parameters and the vdw2 mixing rule. It can be observed, in Figure 6 that for the highest composition of CO2 (0.8002 in mole fraction) the behavior was different than for lower compositions. Near the critical temperature of CO2 (304.21 K), the system has an inflection point; this behavior was already reported in the work of Selva Pereda et al.25 On the other hand, on the right side, with respect to Pedersen et al.,26 it is expected that as long as the squalane concentration is increased, the critical temperature is also increased, yielding a flat curve. These experiments were directly compared with literature data, and average deviations were obtained: AAD_P = 7.3% and MD_P = 6.0%. The number of literature points used was eight.10 It is noteworthy that the conditions of either data sets are not exactly the same. Furthermore, using SRK EoS with the estimated interaction parameters from our experiments for CO2 + C30H62, we have also provided a deviation analysis: AAD_P = 2.88% and MD_P = 6.74%. Table 8 presents the experimental points for the SynNon method for a CO2 mole fraction range of between 0.474 and 0.800 and a temperature range of between 304.05 and 393.65 K. Binary interaction parameters kij and lij of CO2 + C6H10 and CO2 + C30H62 systems were calculated using the experimental measured data of this work. For binary system C6H10 + C30H62, we found no experimental data in the literature. The estimation of interaction parameters kij and lij for C6H10 + C30H62 was calculated with the aid of the UNIFAC contribution group model.27 The Antoine equation was used to describe the vaporpressure data. Antoine constants were estimated with experimental values collected from the literature (DIPPR14), covering the temperature range of interest. Thus, with the UNIFAC and Antoine approaches, PTxy pseudoexperimental data were generated for kij and lij estimations. It is noteworthy that the alpha function parameters were previously calculated using vapor-pressure data. Mathias−Copeman estimated parameters for the studied species are reported in Table 9. The estimated values of kij and lij of the binary systems are reported in Table 10 using phase equilibrium data. For binary system C6H10 + C30H62, the estimation of interaction parameter

Figure 6. P−T diagram for system CO2 + C30H62 at five different compositions in mole fraction: (gray ×) x1 = 0.6030, (gray ●) x1 = 0.4738, (gray ▲) x1 = 0.5622, (gray ⧫) x1 = 0.6854, (gray × with |) x1 = 0.8002, and (gray −) SRK-EOS (kij = 0.1002; lij = 0.0135).

Table 8. Experimental Results for the CO2 (1) + C30H62 (2) System Using the SynNon Methoda x1 (mole fraction)

T/K

P/MPa

0.4738 0.4738 0.4738 0.4738 0.4738 0.5622 0.5622 0.5622 0.5622 0.5622 0.5622 0.5622 0.6030 0.6030 0.6030 0.6030 0.6030

353.25 362.55 374.15 382.75 392.85 332.75 342.85 353.25 363.45 373.65 383.45 393.65 323.25 333.45 343.35 352.65 364.25

5.69 6.16 6.63 6.95 7.37 6.14 6.64 7.21 7.91 8.47 8.90 9.57 6.35 7.26 7.89 8.33 8.94

x1 (mole fraction)

T/K

P/MPa

0.6030 0.6030 0.6854 0.6854 0.6854 0.6854 0.6854 0.6854 0.8002 0.8002 0.8002 0.8002 0.8002 0.8002 0.8002 0.8002

373.15 382.75 304.05 313.25 323.25 333.15 342.95 353.25 313.15 323.45 333.15 343.15 353.35 363.05 373.15 383.25

9.43 10.12 6.29 7.03 8.18 8.83 9.99 10.76 10.38 11.99 12.94 14.40 15.95 17.31 18.56 19.67

a

Standard uncertainties u are u(x1) = 0.005 mol fraction, u(T) = 0.3 K, and u(P) = 0.1 MPa.

between 338.95 and 387.15 K. The experimental data are listed in Table 6. The equilibrium pressure of each bubble point was determined by the intersection of the two curves; the first

Table 9. Mathias−Copeman Estimated Parameters for the Studied Speciesa,b

a

system

C1

C2

C3

AAD_P (%)

MD_P (%)

cyclohexene squalane

0.8586 1.9753

−0.4806 −0.6033

1.0202 −0.3059

0.38 0.47

0.94 1.44

For CO2, the constants were available.28 bCalculations were performed with 100 pseudoexperimental vapor-pressure points.29 E



Article

Table 10. Determination of Interaction Parameters (kij and lij) for the Binary Systems: CO2 (1), C6H10 (2), and C30H62 (3)

a

system

kij

lij

AAD_P (%)a

MD_P (%)b

no. of exp. points

source

C6H10−C30H62 CO2−C30H62 CO2−C6H10

−0.0863 ± 0.0006 0.1002 ± 0.0006 0.1065 ± 0.0020

0.0240 ± 0.0004 0.0135 ± 0.0011 −0.0236 ± 0.0041

1.17 2.87 1.55

2.11 7.99 3.74

331 175 70

UNIFAC27 this work this work

AAD =

100 N

N

∑i = 1

|Pexp, i − Pcalc, i| b MD Pexp, i

=

|Pexp − Pcalc| Pexp

× 100

Table 11. Experimental Results for the CO2 (1) + C6H10 (2) + C30H62 (3) System in Mole Fraction Using the SynVis Methoda

a

x1(mole fraction)

x3(mole fraction)

T/K

P/MPa

x1(mole fraction)

x3(mole fraction)

T/K

P/MPa

0.6414 0.6414 0.6414 0.5949 0.5949 0.5949 0.5949 0.5773 0.5773 0.5773 0.5770 0.5528 0.5528 0.5528 0.5528 0.5528 0.5090

0.0100 0.0100 0.0100 0.0504 0.0504 0.0504 0.0504 0.0952 0.0952 0.0952 0.0952 0.0997 0.0997 0.0997 0.0997 0.0997 0.1489

318.15 328.15 337.95 327.65 337.85 347.90 358.15 334.35 343.55 362.43 383.15 333.15 343.25 352.65 363.05 372.75 323.23

6.740 7.710 8.720 7.940 8.910 9.950 10.980 8.485 9.392 11.234 12.980 7.990 8.970 9.720 10.630 11.470 5.690

0.5090 0.5090 0.5090 0.5090 0.5090 0.5090 0.4569 0.4569 0.4569 0.4569 0.4569 0.4569 0.2333 0.2333 0.2333 0.2333 0.2333

0.1489 0.1489 0.1489 0.1489 0.1489 0.1489 0.1964 0.1964 0.1964 0.1964 0.1964 0.1964 0.0510 0.0510 0.0510 0.0510 0.0510

333.45 343.31 353.27 363.21 373.32 383.25 343.40 353.31 363.07 373.11 383.29 393.25 328.12 353.08 362.48 373.48 383.55

6.458 7.198 7.892 8.593 9.793 10.477 6.775 7.433 8.078 8.370 8.963 9.367 3.237 4.058 4.243 4.540 4.927


Table 12. Experimental Results for the CO2 (1) + C6H10 (2) + C30H62 (3) System Using the SynNon Methoda x1 (mole fraction)

x3 (mole fraction)

T/K

P/MPa

0.5011 0.5011 0.5011 0.5011 0.5773 0.5773 0.5773 0.5773

0.1489 0.1489 0.1489 0.1489 0.0952 0.0952 0.0952 0.0952

323.25 333.45 343.25 353.35 334.35 343.55 362.15 383.15

5.68 6.45 7.22 7.79 8.47 9.39 11.18 13.14


3.3. Ternary System: CO2 + C6H10 + C30H62. Vapor− liquid equilibrium data obtained for ternary system CO2 + C6H10 + C30H62 using the SynVis method in the range of 0.2333 mole fraction of CO2 up to 0.6414 and a mole fraction of squalane of between 0.0100 and 0.0997 in the range of temperature of 318.15 up to 393.25 K are listed in Table 11. In Figure 7, the experimental results in the form of a P−T diagram for the system CO2 + C6H10 + C30H62 are presented, using the SynVis method. The vapor−liquid equilibrium data were described with the Soave−Redlich−Kwong7 equation of state, with Mathias−Copeman8 alpha function parameters and vdw2 mixing rule. The binary interaction parameters presented earlier were used to predict the ternary system behavior. Quantitative agreement between our measured data with the thermodynamic model can be observed. The SynNon method was also used for a few points for two compositions of CO2 and squalane in the temperature range

Figure 7. P−T diagram for the system CO2 + C6H10 + C30H62 at four different CO2 and C30H62 compositions, with values of kij and lij reported in Table 10: (gray × with |) xCO2 = 0.595 and xC30H62= 0.050; (gray ▲) xCO2 = 0.233 and xC30H62 = 0.051; (gray ×) xCO2 = 0.5090 and xC30H62 = 0.1489; (gray ⧫) xCO2 = 0.4569 and xC30H62 = 0.1964; and SRKEoS.

kij was also obtained using a group contribution expression.23 The value was very close to the approach using UNIFAC pseudodata30 and the group contribution expression for kij, demonstrating coherence. F



Article

The SynVis method has the operational difficulty to observe the first vapor bubble. On the other hand, the nonvisual method is not based on the observation of the mixture in the cell but on the recording of equilibrium pressure attained at different volumes of the cell at constant composition and temperature. It was shown that the P−V method is accurate and reliable and can be used when the sample is not translucent and the observation of the cell contents is not possible.

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Fedra A. V. Ferreira: 0000-0003-2480-4866 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS Financial support provided by ANP (Agência Nacional do ́ Petróleo, Gás Natural e Biocombustiveis), CNPq (Conselho ́ Nacional de Desenvolvimento Cientifico e Tecnológico), CAPES (Coordenaçaõ de Aperfeiçoamento de Pessoal de ́ Superior), and Petrobras is gratefully acknowledged. Nivel

Figure 8. Experimental versus calculated bubble pressure for ternary system CO2 + C6H10 + C30H62.

■

between 323.25 and 383.15 K. Experimental data are listed in Table 12. The equilibrium pressure of each bubble point was determined by the intersection of the monophase and twophase curves using the same procedure presented earlier for the binary system. The binary interaction parameters calculated earlier were now used to predict the behavior of ternary system CO2 + C6H10 + C30H62. The maximum deviation, in the determination of bubble pressure, between the SynVis method and the SynNon method is 1.25%. Experimental bubble pressure values against calculated ones using SRK EoS with vdW2 for the ternary system are presented in Figure 8. The average deviation between the experimental and calculated data is AAD_P = 0.20 MPa, and the maximum deviation is MD_P = 0.49 MPa.

REFERENCES

(1) Christov, M.; Dohrn, R. High-pressure fluid phase equilibria: Experimental methods and systems investigated (1994−1999). Fluid Phase Equilib. 2002, 202, 153−218. (2) Dohrn, R.; Brunner, G. High-pressure fluid-phase equilibria: Experimental methods and systems investigated (1988−1993). Fluid Phase Equilib. 1995, 106, 213−282. (3) Pfohl, O.; Petersen, J.; Dohrn, R.; Brunner, G. Partitioning of carbohydrates in the vapor-liquid-liquid region of the 2-propanol + water + carbon dioxide system. J. Supercrit. Fluids 1997, 10, 95−103. (4) Dohrn, R.; Peper, S.; Fonseca, J. M. S. High-pressure fluid-phase equilibria: Experimental methods and systems investigated (2000− 2004). Fluid Phase Equilib. 2010, 288, 1−54. (5) Fonseca, J. M. S.; Dohrn, R.; Peper, S. High-pressure fluid-phase equilibria: Experimental methods and systems investigated (2005− 2008). Fluid Phase Equilib. 2011, 300, 1−69. (6) Gardner, P. M.; Whitehead, E. V. The Isolation of Squalane from a Nigerian Petroleum. Geochim. Cosmochim. Acta 1972, 36, 259−263. (7) Soave, G. Equilibrium constants from a modified Redlich-Kwong equation of state. Chem. Eng. Sci. 1972, 27, 1197−1203. (8) 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. (9) Mokbel, I.; Blondel-Telouk, A.; Vellut, D.; Jose, J. Vapor−liquid equilibria of two binary mixtures: benzene+n-tetradecane and benzene +squalane. Fluid Phase Equilib. 1998, 149, 287−308. (10) Brunner, G.; Saure, C.; Buss, D. Phase Equilibrium of Hydrogen, Carbon Dioxide, Squalene, and Squalane. J. Chem. Eng. Data 2009, 54, 1598−1609. (11) Liphard, K.; Schneider, G. Phase equilibria and critical phenomena in fluid mixtures of carbon dioxide + 2,6,10,15,19,23hexamethyltetracosane up to 423 K and 100 MPa. J. Chem. Thermodyn. 1975, 7, 805−814. (12) Chai, C.-P.; Paulaitis, M. E. Gas solubilities of carbon dioxide in heavy hydrocarbons. J. Chem. Eng. Data 1981, 26, 277−279. (13) Sovová, H.; Jez, J.; Khachaturyan, M. Solubility of squalane, dinonyl phthalate and glycerol in supercritical CO2. Fluid Phase Equilib. 1997, 137, 185−191. (14) Rowley, R. L.; Wilding, W. V.; Oscarson, J. L.; Zundel, N. A.; Marshall, T. L.; Daubert, T. E.; Danner, R. P. DIPPR & registered

4. CONCLUSIONS The apparatus is capable of operating at temperatures of up to 393 K and at pressures of up to 30 MPa over the whole concentration range. The performance of the cell was tested by measuring vapor−liquid equilibrium data of a well-known binary system in the literature: carbon dioxide + ethanol. A series of new data were measured, at several temperatures, pressures and compositions, for the carbon dioxide + cyclohexene, carbon dioxide + squalane, and carbon dioxide + cyclohexene + squalane systems. The agreement between visual and nonvisual methods was observed to be within 1%. Furthermore, the nonvisual method presents less operational uncertainty. Vapor−liquid equilibrium data were properly described using the Soave−Redlich−Kwong EoS with the Mathias−Copeman alpha function and the classical quadratic mixing rule (vdw2). It is demonstrated that the interaction parameters estimated from binary data (CO2 + C6H10 and CO2 + C30H62) also quanThetitatively described the studied ternary system, i.e., carbon dioxide + cyclohexene + squalane. The phase envelope calculation was also demonstrated to be coherent with the applied equation of state. G



Article

Data Compilation of Pure Compound Properties. Design Institute for Physical Properties; AIChE: New York, 2002. (15) Guerra-Neto, D.; de, B.; Ferreira-Pinto, L.; Giufrida, W. M.; Zabaloy, M. S.; Cardozo-Filho, L.; Chiavone-Filho, O. Bubble Point Determination for CO 2 + Ethanol + Alkanolamines (Monoethanolamine, Diethanolamine, or Triethanolamine) at High Pressures. J. Chem. Eng. Data 2014, 59, 3319−3323. (16) do Prado, I. M.; Giufrida, W. M.; Alvarez, V. H. Phase Equilibrium Measurements of Sacha Inchi Oil (Plukenetia volubilis) and CO2 at High Pressures. J. Am. Oil Chem. Soc. 2011, 88, 1263− 1269. (17) Favareto, R.; Fregadolli, P. H.; Cabral, V. F.; Antunes, O. A. C.; Cardozo-Filho, L. Phase Equilibria of Acrylonitrile and p -Bromobenzaldehyde in Carbon Dioxide. J. Chem. Eng. Data 2008, 53, 1080− 1084. (18) Pinto, L. F.; Rodriguez-Reartes, S. B.; Corazza, M. L. Phase behavior of carbon dioxide+medroxyprogesterone acetate system at high pressures. Fluid Phase Equilib. 2013, 349, 1−11. (19) Fele Ž ilnik, L.; Grilc, M.; Levec, J.; Peper, S.; Dohrn, R. Phaseequilibrium measurements with a novel multi-purpose high-pressure view cell: CO2 + n-decane and CO2 + toluene. Fluid Phase Equilib. 2016, 419, 31−38. (20) Galicia-Luna, L. A.; Ortega-Rodriguez, A.; Richon, D. New Apparatus for the Fast Determination of High-Pressure Vapor−Liquid Equilibria of Mixtures and of Accurate Critical Pressures. J. Chem. Eng. Data 2000, 45, 265−271. (21) Jennings, D. W.; Lee, R. J.; Teja, A. S. Vapor-liquid equilibria in the carbon dioxide + ethanol and carbon dioxide + 1-butanol systems. J. Chem. Eng. Data 1991, 36, 303−307. (22) Pfohl, O.; Pagel, A.; Brunner, G. Phase equilibria in systems containing o-cresol, p-cresol, carbon dioxide, and ethanol at 323.15− 473.15 K and 10−35 MPa. Fluid Phase Equilib. 1999, 157, 53−79. (23) Tsivintzelis, I.; Missopolinou, D.; Kalogiannis, K.; Panayiotou, C. Phase compositions and saturated densities for the binary systems of carbon dioxide with ethanol and dichloromethane. Fluid Phase Equilib. 2004, 224, 89−96. (24) Wu, W.; Ke, J.; Poliakoff, M. Phase Boundaries of CO2 + Toluene, CO2 + Acetone, and CO 2 + Ethanol at High Temperatures and High Pressures. J. Chem. Eng. Data 2006, 51, 1398−1403. (25) Prieto, M. G.; Sánchez, F. A.; Pereda, S. Multiphase Equilibria Modeling with GCA-EoS. Part I: Carbon Dioxide with the Homologous Series of Alkanes up to 36 Carbons. Ind. Eng. Chem. Res. 2015, 54, 12415−12427. (26) Pedersen, K. S.; Christensen, P. L.; Shaikh, J. A. Phase Behavior of Petroleum Reservoir Fluids; Taylor & Francis; CRC Press: Boca Raton, FL, 2007. (27) Holderbaum, T.; Gmehling, J. PSRK: A Group Contribution Equation of State Based on UNIFAC. Fluid Phase Equilib. 1991, 70, 251−265. (28) Dahl, S.; Fredenslund, A.; Rasmussen, P. The MHV2 model: a UNIFAC-based equation of state model for prediction of gas solubility and vapor-liquid equilibria at low and high pressures. Ind. Eng. Chem. Res. 1991, 30, 1936−1945. (29) Mathias, P. M.; Copeman, T. W. Extension of the PengRobinson equation of s:tate to complex mixtures: evaluation of the various forms of the local composition concept. Fluid Phase Equilib. 1983, 13, 91−108. (30) Qian, J. W.; Jaubert, J. N.; Privat, R. Prediction of the phase behavior of alkene-containing binary systems with the PPR78 model. Fluid Phase Equilib. 2013, 354, 212−235.

H


VaporâLiquid Equilibrium Measurements for Carbon Dioxide +

Recommend Documents

VaporâLiquid Equilibrium Measurements for Carbon Dioxide +