Article pubs.acs.org/jced
Isobaric Vapor−Liquid Equilibrium for the Binary System of Hexamethyl Disiloxane + Isopropyl Acetate at Atmospheric Pressure Wenlin Zhang,*,† Xiaowen Wang,† Nan Meng,*,†,‡ Wei Du,† and Chunli Li† †
School of Chemical Engineering, Hebei University of Technology, Tianjin 300130, P.R. China School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, P.R. China
‡
ABSTRACT: Isobaric vapor−liquid equilibrium (VLE) data for the hexamethyl disiloxane + isopropyl acetate system at atmospheric pressure (101.3 kPa) were measured. The thermodynamic consistency of experimental data was checked with the Herrington method. The experimental binary data were correlated with Wilson, nonrandom two-liquid (NRTL), and universal quasichemical (UNIQUAC) two-parameter models. All three models satisfactorily fitted with the experimental data and the Wilson model was the most suitable one to represent the VLE data. The result showed that the standard deviations of the Wilson model in temperature and vapor phase were 0.2279 and 0.0568, respectively. The system presents a minimum temperature azeotrope at 361.12 K with the mole fraction of hexamethyl disiloxane as 0.1572.
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INTRODUCTION Hexamethyl disiloxane (HMDSO, 1) is a significant chemical, which is widely used in organic chemical and the pharmaceutical industry.1,2 Isopropyl acetate (IPAC, 2), widely used in paintings, printing inks, and binders for its excellent alkali-resistance, hydrophobicity, and good capacity to dissolve plastics and acetic based fibers, is an important fruity fragrance intermediate in the organic synthesis industry. Isopropyl acetate has similar physical and chemical properties to ethyl acetate and buty acetate, which makes it possible to replace them in many cases such as textiles, plastics, and papermaking. Therefore, isopropyl acetate is considered to be a “solvent of the future”.1 However, there is little VLE data for those systems at present. Only the VLE data for hexamethyl disiloxane + ethyl acetate and hexamethyl disiloxane + sec-butyl acetate systems were determined.2,3 In this paper, isobaric T−x−y data for the HMDSO (1) + IPAC (2) system were measured at 101.3 kPa. The thermodynamic consistency of this system was established using the Herington method. Finally, the Wilson,4 NRTL,5 and UNIQUAC6 models were used to fit with the experimental data.
determination condition can be seen in Sample Analysis section. The published values for these reagents are shown in Table 1.7 Table 1. Properties of the Pure Components HMDSO (1)
IPAC (2)
EAC(3)
C6H18Si2O 162.38 373.67 518.70 1.91
C5H10O2 102.13 361.65 532.00 3.29
C4H8O2 88.11 350.21 523.30 3.88
The molar liquid volumes for the pure components used in Wilson model, and volume and area parameters for pure components used in UNIQUAC model were shown in Table 2. Apparatus and Procedure. The VLE data were determined by a modified double circulating still of Othmer type and shown in Figure 1. About 50 cm3 of a mixture of given
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Table 2. Parameters of the Pure Components Used in the Wilson and UNIQUAC Models
EXPERIMENTAL SECTION Chemicals. HMDSO (AR grade), purified by atmospheric distillation, was supplied by Shanghai Nuotai Chemical Factory. IPAC (HPLC) was purchased from Tianjin Guangfu Fine Chemical Research Institute. Ethyl acetate (EAC, AR grade) was supplied by Tianjin Reagent Factory. All reagents were tested by gas chromatography (GC) and no obvious impurity was detected. The purity of the samples was not less than 0.9995 in the mole fraction. The © XXXX American Chemical Society
property formula MW/g·mol−1 Tb/K Tc/K Pc/MPa
property
HMDSO (1)
IPAC (2)
EAC(3)
Vi/m3·kmol−1 θi ϕi
0.21378 5.66800 6.96770
0.11758 3.65200 4.15220
0.09854 3.11600 3.47860
Received: March 6, 2013 Accepted: August 1, 2013
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dx.doi.org/10.1021/je400245u | J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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Figure 1. Double circulating still.
content was injected in the boiling chamber and heated. Some boiled liquid taken with some vapor spilled through the riser to the separator room. The liquid was separated from the vapor and dropped into the liquid-phase sample effusion slot. The vapor was congealed in the hydrocooling condenser and dropped down to the vapor-sample effusion slot. Liquid from two effusion slots mixed with each other and flowed back to the boiling chamber where they were heated continuously. The digital thermometer, the accuracy less than 0.1 K, was used to measure the system temperature. The system reached the boiling temperature within 0.5 h and kept the equilibrium state for about 1.5 h. The device pressure was kept constant by using a vacuum pump. Pressure was measured by a U-type differential manometer.8 Sample Analysis. Liquid and vapor phase equilibrium compositions were determined by a gas chromatography (GC, SP-3420A, BeiFen Co.). The GC was equipped with a hydrogen flame ionization detector (FID) and a capillary column (HJ-OV-1701, 30 m in length, 0.32 mm in diameter, and 0.5 μm film thicknesses). The column, injector, and detector temperatures were 353.15 K, 453.15 K, and 453.15 K, respectively. Nitrogen was flowed at 30 mL·min−1. High-purity hydrogen and compressed air were maintained 30 mL·min−1 and 300 mL·min−1, respectively. A 0.2 μL sample was injected in the GC as a test. Each sample was analyzed at least thrice to verify an accuracy within ± 0.003. A series of standard mixtures were used to calibrate the GC data.
Figure 2. y−x diagram for IPAC (2) + EAC (3).
γi = Pyi /xiPis
(1)
The vapor pressure of pure component was obtained by the five parameter Antoine equation as follows: ln pis = a +
b + c ln T + dT e T
f≤T≤g
(2)
where a ≈ e were specific parameters of the equation and f and g were the scopes of application temperatures. The specific parameters were shown in Table 4. The thermodynamic consistency of this system was checked with the Herington method.9 In accordance with this method, D = 2.09, J = 4.97, and D − J = −2.88 which less than 10. Consequently, the experimental data conformed to the Herington test. The result was showed in Figure 3. Correlation of the VLE System. Wilson, NRTL (α = 0.310,11), and UNIQUAC equations were used to correlate the VLE data. The minimization of the objective function was used to obtain the equation parameters as follows:
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RESULTS AND DISCUSSION Experimental Data. The VLE data of 2-propyl acetate (IPAC, 2) + ethyl acetate (EAC, 3) system, compared with the literature data, were used to check the suitability of the equilibrium still.2 The results are shown in Figure 2. From Figure 2, the measured VLE data were fitted well with the literature data. It shows that the equilibrium still is suitable for this measurement. The VLE data of the HMDSO (1) + IPAC (2) system were acquired at 101.3 kPa and are shown in Table 3. Thermodynamic Consistency Test. Because the device pressures were sufficiently low in the experimental system, the vapor phase could be approximated as ideal gas. The activity coefficients equation was simplified as
2 ⎛⎡ 2 ⎡y − ycal, i ⎤ ⎞ Texp , i − Tcal, i ⎤ exp , i ⎜ ⎟ ⎢ ⎥ + ⎥ ∑ ⎜⎢ σ σ ⎢ ⎥ ⎦ ⎣ ⎣ ⎦ ⎟⎠ y T i=1 ⎝ N
F=
B
(3)
dx.doi.org/10.1021/je400245u | J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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Table 3. VLE Data for the HMDSO (1) + IPAC (2) System at 101.3 kPaa
a
Table 5. Binary Interaction Parameters of Wilson, NRTL, and UNIQUAC Models
T/K
y1
y2
x1
x2
Wilson
NRTL
UNIQUAC
361.27 361.05 360.95 360.87 360.85 360.90 361.00 361.05 361.35 361.55 362.00 362.45 363.07 363.87 364.75 365.80 367.15 368.75 370.85
0.0364 0.0755 0.1080 0.1416 0.1707 0.2023 0.2282 0.2613 0.2929 0.3200 0.3519 0.3853 0.4372 0.4868 0.5319 0.5959 0.6598 0.7491 0.8528
0.9636 0.9245 0.8920 0.8584 0.8293 0.7977 0.7718 0.7387 0.7071 0.6800 0.6481 0.6147 0.5628 0.5132 0.4681 0.4041 0.3402 0.2509 0.1472
0.0291 0.0662 0.0996 0.1374 0.1735 0.2102 0.2532 0.2981 0.3411 0.3863 0.4435 0.5000 0.5530 0.6044 0.6692 0.7300 0.7983 0.8621 0.9363
0.9709 0.9338 0.9004 0.8626 0.8265 0.7898 0.7468 0.7019 0.6589 0.6137 0.5565 0.5000 0.4470 0.3956 0.3308 0.2700 0.2017 0.1379 0.0637
ln Aij = Bij/T −3247.1251 −172.7449 −0.131 0.488 0.2279 3.51·10−5 1.42·10−2 0.0568
τij = Bij/T −55.1211 271.5952 −0.125 0.488 0.2002 2.81·10−3 1.97·10−2 0.0681
τij = exp(Bij/T) −424.32738 −1074.5594 −0.131 0.488 0.2256 4.51·10−4 −1.48·10−2 0.0598
B12 B21 ΔTAD ΔTMD σT ΔyAD ΔyMD σy
data are shown in Figure 4. The system presents a minimum temperature azeotrope at 361.12 K and the mole fraction of hexamethyl disiloxane as x1 = 0.1572.
u(T) = 0.05 K and u(x) = u(y) = 0.001.
Table 4. Antoine Equation Parameters HMDSO (1) temperature units pressure units a b c d e f g
IPAC (2)
EAC (3)
K
K
K
MPa 37.1135 −5597 −4.1262 6.3815·10−18 6 204.93 518.7
MPa 35.9385 −5563.9 −3.8789 2.4755·10−18 6 199.75 532
MPa 53.0085 −6227 −6.4100 1.7914·10−18 6 189.6 523.3
Figure 4. T−x−y diagram for HMDSO (1) + IPAC (2).
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CONCLUSIONS The isobaric VLE data for HMDSO (1) + IPAC (2) system were measured at atmospheric pressure by using a modified double circulating still. Experimental data were correlated by Wilson, NRTL, and UNIQUAC models. The standard deviations of the Wilson model in temperature and in vapor phase were 0.2279 and 0.0568, respectively. The system presents a minimum temperature azeotrope at 361.12 K with the mole fraction of hexamethyl disiloxane as x1 = 0.1572. These data will be useful to calculate and design a special distillation plant.
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AUTHOR INFORMATION
Corresponding Author
Figure 3. Herington test.
*Tel.: +086-022- 60202248. Fax: +086-022- 60202248. E-mail:
[email protected] (W.L.Z.). Tel.: +086-022-27890643. Fax: +086-022-27890643. E-mail:
[email protected] (N.M.).
In this calculation, σT was set to 0.2 K and σy was set to 0.05. The calculated results of the equation binary parameters are shown in Table 5. From Table 5, the average absolute deviation (AD) in temperature approached 0.13 K. However, the AD and the maximum deviation (MD) of the Wilson model in the vapor phase composition were much better than with the other two models. Wilson model compared with the experimental T−x−y
Author Contributions
The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes
The authors declare no competing financial interest. C
dx.doi.org/10.1021/je400245u | J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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ABBREVIATIONS MW molecular weight, g·mol−1 Tb normal boiling point, K Tc critical temperature, K Pc critical pressure, MPa V molar liquid volume for pure components used in Wilson model, m3·kmol−1 θ area parameter for pure components used in UNIQUAC model φ volume parameter for pure components used in UNIQUAC model xi liquid phase mole fraction of component i yi vapor phase mole fraction of component i T temperature, K γi activity coefficients of the component i P total pressure, MPa Psi vapor pressure of pure component i, MPa N the number of the experimental data σ standard deviation of the measured variables AD average absolute deviation MD maximum deviation xi′ liquid phase mass fraction of component i yi′ vapor phase mass fraction of component i
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REFERENCES
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