Article pubs.acs.org/jced
Isobaric Vapor−Liquid Equilibria of Binary Systems (Propyl Acetate + n‑Pentanol), (Propyl Acetate + 1‑Methyl-1-butanol), and (Propyl Acetate + 3‑Methyl-1-butanol) at 101.3 kPa Jinli Zhang, Yulong Liu, Nan Meng, Wei Li, and Minqing Zhang* School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, PR China
ABSTRACT: Isobaric vapor−liquid equilibrium (VLE) data have been measured at 101.3 kPa for the binary mixtures containing (propyl acetate + n-pentanol), (propyl acetate + 1-methyl-1-butanol), and (propyl acetate + 3-methyl-1-butanol) using an equilibrium still. The thermodynamic consistency of the experimental data was tested by semiempirical methods of Herington and was satisfactory. The activity coefficients were correlated with the NRTL, Wilson, and UNIQUAC models, and the NRTL model indicates slightly better results than the other two models in these three binary systems.
1. INTRODUCTION Along with more attentions of world oil resources, public health, and the environment, Fischer−Tropsch (F-T) synthesis has been reconsidered as a research focus to produce high value liquid fuels, including mixed-hydrocarbons and mixed-alcohols.1−4 Depending on the kinds of catalysts, the composition of mixed-alcohols includes low-carbon alcohols with the carbon number ranging from 1 to 5, besides small amounts of esters, acids, etc. To produce these alcohol compositions with high purity, it is fundamental to establish the related vapor−liquid equilibrium (VLE) data, which is necessary for the development of separation processes involving distillation, membrane-distillation, etc. There have been reports of VLE data for the systems of (methanol + propyl acetate),5 and (propyl acetate + ethanol, or n-propanol/1-methyl-1-ethanol, or n-butanol/1-methyl-1propanol);6 however, no literature has been found about the binary system involving C5 alcohol and propyl acetate. We used the Aspen Plus software to simulate the separation of C5 alcohol and propyl acetate, the simulation results turned out to be inconsistent with the experimental data. Therefore, it is important to measure the data of the C5 alcohol and propyl acetate system for reliable process simulation. In this paper, the vapor−liquid equilibrium of the system (propyl acetate + n-pentanol, or 1-methyl-1-butanol, or 3-methyl-1-butanol) has been studied experimentally, followed by a thermodynamic consistency check using the semiempirical methods of Herington,7 as well as the correlations using NRTL,8 Wilson,9 and UNIQUAC10 models.
and liquid phases were continuously circulated to ensure that the vapor−liquid equilibrium was established rapidly. The condenser was cooled with circulated water at T = 283.15 ± 1 K to minimize the vapor phase loss during the VLE measurement. Vapor and liquid sample connections were sealed with Teflon tape to prevent vapor phase from leaking. A series of standard samples including propyl acetate and n-pentanol, or 1-methyl-1-butanol, or 3-methyl-1-butanol were prepared with a concentration interval of 5 %, using an analytic balance with a readability of ± 0.1 mg. The system was flushed by ethanol and the standard sample at least twice in order to eliminate any contaminants inside the system. After cleaning, a certain amount of standard sample was supplied into the equilibration cell using an injector. In every experiment, the equilibrium was reached after the temperature, the vapor composition, and the liquid composition was maintained constant for at least 90 min. The equilibrium temperature was measured with a thermometer of which the uncertainty was ± 0.2 K. A type HJ-WAX gas chromatograph with a flame-ionization detector and a column 50 m long, 0.5 μm in film thickness, and 0.32 mm in diameter was used to analyze the vapor and liquid composition of the binary systems. 2.2. Chemicals. Propyl acetate (GR grade, + 99 %), and 1-methyl-1-butanol (GR grade, + 99 %) were purchased from Alfa Aesar, n-pentanol (GR grade, + 99 %) and 3-methyl-1-butanol (GR grade, + 99 %) were purchased from Tianjin Kemiou Chemical Reagent Co., Ltd. in China. The purity of all substances
2. EXPERIMENTAL SECTION 2.1. Apparatus and Procedure. An equilibrium still was used for the VLE measurement, as shown in Figure 1. Both vapor
Received: August 8, 2013 Accepted: September 20, 2013
© XXXX American Chemical Society
A
dx.doi.org/10.1021/je4007184 | J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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Table 3. VLE Data for Binary System of (Propyl Acetate (1) + n-Pentanol (2)) at P = 101.3 kPaa
Figure 1. Experimental apparatus. (1) circulated water outlet; (2) thermometer; (3) vacuum heated insulative coat; (4) liquid phase sample connection; (5) liquid phase sample storage; (6) boiling room; (7) heating rod; (8) vapor−liquid mixed room; (9) vapor phase sample storage; (10) vapor phase sample connection; (11) circulated water inlet; (12) condenser.
no.
T/K
x1
y1
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
376.3 377.6 379.0 380.3 381.8 383.2 384.6 386.2 387.7 389.3 390.9 393.9 395.3 397.1 399.8 401.5 403.9 406.1 409.5
0.943 0.895 0.842 0.787 0.735 0.684 0.628 0.584 0.533 0.472 0.424 0.361 0.317 0.266 0.219 0.178 0.120 0.079 0.032
0.978 0.949 0.942 0.921 0.892 0.873 0.848 0.827 0.796 0.756 0.722 0.647 0.600 0.567 0.486 0.411 0.331 0.229 0.108
a
x1 is the mole fraction of propyl acetate in the liquid phase; y1 is the mole fraction of propyl acetate in the vapor phase. Standard uncertainties u are u(T) = 0.2 K, u(P) = 0.1 kPa, and u(x1) = u(y1) = 0.003.
Table 1. Suppliers and Purities of the Used Chemicals chemical name propyl acetate n-pentanol 3-methyl-1-butanol 1-methyl-1-butanol
mole fraction purity as determined by GC
supplier Alfa Aesar Tianjin Kemiou Chemical Reagent Co., Ltd. Tianjin Kemiou Chemical Reagent Co., Ltd. Alfa Aesar
3.2. Thermodynamics Consistency Verification. All experimental binary VLE data were tested for thermodynamic consistency using the method of Herington7 in order to ensure the thermodynamics consistency of these systems. There were rules and constraints that the value of (D−J) must be less than 10 for this method.
0.995 0.998 0.998 0.995
1
D = 100
was checked with gas chromatography analysis, and the results are shown in Table 1. To examine the purity of the substances, the densities of all substances were measured by pycnometer method at T = 298.15 K and refractive index values at T = 298.15 K by using a refractometer (WAY-2W, Shanghai Precision Scientific Instrument Co., Ltd., China). Normal boiling points Tb of pure components were measured by the equilibruim still. The experimental values show good agreement when compared with the literature. The results are obviously indicated in Table 2.
∫0 ln(γ1/γ2) dx1 1
∫0 |ln(γ1/γ2)| dx1 J = 150
(1)
Tmax − Tmin Tmin
(2)
where γ1 is activity coefficient of propyl acetate, γ2 is activity coefficient of n-pentanol or 3-methyl-1-butanol or 1-methyl-1butanol, Tmax/K and Tmin/K are the highest and the lowest temperature in the system. The results of thermodynamics consistency verification are demonstrated in Table 6 and Figure 3 panels a, b, and c, which obviously indicate that the experimental VLE data of three binary systems were nearly in conformity with thermodynamics consistency. 3.3. Data Correlation. Assuming the vapor phase is an ideal gas under low or moderate pressure, the activity coefficients of the components were calculated from eq 3:
3. RESULTS AND DISCUSSION 3.1. Binary Systems. Experimental results of VLE data (T, xi, yi) for the three binary mixtures involved in this study were presented in Table 3, Table 4, and Table 5. The corresponding phase diagrams are successively shown in Figure 2 panels a, b, and c, which reveal that there is no azeotropic behavior in any measured binary systems.
γi = yp /(xipis ) i
(3)
Table 2. Density, ρ, Index of Refraction, nD, and Normal Boiling Points, Tb, of Pure Componentsa ρ(298.15 K)/(kg·m−3) component propyl acetate n-pentanol 1-methyl-1-butanol 3-methyl-1-butanol a
expt 882.80 810.12 811.04 806.57
nD (298.15 K)
lit
expt 11
883.03 810.8012 812.0013 807.1014
1.3821 1.4078 1.4155 1.4048
Tb/K lit 11
1.3828 1.408012 1.416013 1.405214
expt
lit15
374.60 410.90 392.20 404.20
374.65 410.90 392.20 404.15
Standard uncertainties u are u(T) = 0.2 K. B
dx.doi.org/10.1021/je4007184 | J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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Table 4. VLE data for Binary System of (Propyl Acetate (1) + 3-Methyl-1-butanol (2)) at P = 101.3 kPaa no.
T/K
x1
y1
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
376.3 377.4 378.3 379.4 380.9 382.0 383.3 384.6 385.8 387.1 388.7 390.2 391.6 393.0 395.1 396.3 398.0 400.3 402.3
0.941 0.891 0.841 0.792 0.739 0.687 0.636 0.584 0.527 0.482 0.432 0.375 0.331 0.276 0.230 0.182 0.133 0.083 0.034
0.968 0.952 0.925 0.902 0.882 0.845 0.822 0.791 0.755 0.713 0.683 0.646 0.577 0.526 0.466 0.404 0.319 0.217 0.108
a
x1 is the mole fraction of propyl acetate in the liquid phase; y1 is the mole fraction of propyl acetate in the vapor phase. Standard uncertainties u are u(T) = 0.2 K, u(P) = 0.1 kPa, and u(x1) = u(y1) = 0.003.
Table 5. VLE Data for Binary System of (Propyl Acetate (1) + 1-Methyl-1-butanol (2)) at P = 101.3 kPaa no.
T/K
x1
y1
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
375.7 376.7 377.3 378.0 378.8 379.6 380.3 381.1 381.8 382.8 383.7 384.7 385.5 386.5 387.5 388.6 389.7 390.6 391.7
0.951 0.887 0.839 0.787 0.739 0.690 0.637 0.587 0.540 0.486 0.438 0.386 0.337 0.290 0.233 0.190 0.142 0.094 0.049
0.967 0.932 0.895 0.868 0.831 0.791 0.759 0.724 0.682 0.643 0.590 0.541 0.494 0.443 0.373 0.314 0.245 0.175 0.090
Figure 2. Temperature−vapor and liquid composition relationships: ■, experimental T−x1; and □, experimental T−y1; red , NRTL; green -,Wilson; and black ---, UNIQUAC. (a) (Propyl acetate (1) + n-pentanol (2)) at 101.3 kPa; (b) (propyl acetate (1) + 3-methyl1-butanol (2)) at 101.3 kPa; (c) (propyl acetate (1) + 1-methyl-1butanol (2)) at 101.3 kPa.
a
x1 is the mole fraction of propyl acetate in the liquid phase; y1 is the mole fraction of propyl acetate in the vapor phase. Standard uncertainties u are u(T) = 0.2 K, u(P) = 0.1 kPa, and u(x1) = u(y1) = 0.003.
Table 6. Thermodynamics Consistency Test for Three Binary Systems at 101.3 kPa
where psi is the saturated vapor pressure of a pure substance at the boiling temperature which can be calculated with the Antoine eq 4, where A, B, and C are Antoine coefficients, and T is the temperature (K); yi is the vapor phase mole fraction and xi is the liquid phase mole fraction. log(pis /kPa) = A − B/(T /K + C)
mixture
D
J
D−J < 10
propyl acetate + n-pentanol propyl acetate +3-methyl-1-butanol propyl acetate +1-methyl-1-butanol
13.1 21.0 14.7
14.6 11.8 7.00
−1.50 9.20 7.70
The Antoine coefficients14 for the pure components are shown in Table 7. The nonrandomness parameter αij was set at 0.3 in the
(4) C
dx.doi.org/10.1021/je4007184 | J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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Table 7. Antoine Coefficient of Pure Components within the Temperature Region ΔT in this Study Antoine coefficients compound
A
B
C
ΔT/K
propyl acetate n-pentanol 1-methyl-1-butanol 3-methyl-1-butanol
6.48937 6.39750 6.34413 6.17508
1544.310 1337.613 1252.400 1201.770
−30.623 −106.567 −104.180 −115.830
374 to 542 326 to 411 274 to 393 303 to 412
Table 8. Physical Parameters and Properties of the Pure Componentsa compound
Tc/K
Pc/kPa
Zc
ω
r
q
propyl acetate n-pentanol 1-methyl-1-butanol 3-methyl-1-butanol
549.73 588.10 561.00 577.20
3360 3897 3700 3930
0.254 0.258 0.259 0.269
0.3889 0.5748 0.5550 0.5900
4.153 4.129 4.283 4.273
3.656 3.592 3.556 3.478
a
Taken from Aspen property databank.
⎡⎛ exp cal ⎞2 ⎛ T exp − T cal ⎞2 ⎤ ⎢⎜ yij − yij ⎟ j j ⎟⎥ + ⎜⎜ OF = ∑ ∑ ⎢ ⎟⎥ ⎜ ⎟ σ σ y T ⎝ ⎠ ⎥⎦ N i ⎢ ⎠ ⎣⎝
(6)
where y is the mole fraction of the pure component in the vapor phase; i represents each pure component in the binary mixtures; N represents the number of the lines in each Table 3, Table 4, and Table 5; σ is the standard deviation of the measured experimental values. We use the average absolute deviations (AAD)16,17 to measure the agreement between the experimental results and the calculated values. The average absolute deviation was calculated by AAD =
NRTL model. The molar volumes necessary for the Wilson equation were calculated with the following: RTci ti Zci , Pci
ti = 1 + (1 − T /Tci)2/7 ,
N
∑ |Ciexp − Cical| k=1
(7)
where Ci represents the independent variable of the pure component i. Temperature−vapor and liquid composition relationships for three binary systems at P = 101.3 kPa are successively shown in Figure 2 panels a, b, and c, with the curve fitting by NRTL, Wilson, and UNIQUAC equations.18,19 It is indicated that all the three models can provide a relative accurate prediction of VLE data of the binary systems of (propyl acetate + n-pentanol), (propyl acetate + 1-methyl-1-butanol), and (propyl acetate + 3-methyl-1-butanol). According to the binary parameters and the AAD of the three systems, as listed in Table 9, the prediction accuracy using the NRTL model is a little bit better than that using Wilson and UNIQUAC models. For example, in the binary system of (propyl acetate + 3-methyl-1-butanol), the NRTL correlation shows the best deviation of y1 = 0.0122, whereas the Wilson and UNIQUAC correlations present larger deviation with y1 = 0.0127 and y1 = 0.0148, respectively. It is known that Wilson model is applicable to polar and nonpolar mixtures, especially to provide accurate predictions for hydrocarbon and alcohol systems. However the Wilson model is not appropriate for partially miscible liquid mixtures. The UNIQUAC model, based on the quasi-lattice model and the local composition concept, is a strong theoretical model, which is established by the theory of a liquid−liquid system, while the NRTL model is applicable to both miscible and immiscible liquid mixtures. Thus, it is reasonable for a binary system of (propyl acetate + C5 alcohol) that these three activity coefficient
Figure 3. Plot of ln(γ1/γ2) versus x1. the red line is the calculated value of Herington test. (a) (propyl acetate + n-pentanol); (b) (propyl acetate + 3-methyl-1-butanol); (c) (propyl acetate + 1-methyl-1-butanol).
Vi =
1 N
T /Tci ≤ 0.75 (5)
where Tci, Pci, Zci are shown in Table 8. For the UNIQUAC model, both the area parameters q and the molar volume parameters r are indicated in Table 8. The objective function OF for the calculation can be calculated with eq 6: D
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Table 9. The Binary Parameters Calculated from the NRTL,a Wilson, and UNIQUAC Models and Average Absolute Deviations for the Temperature and Vapor Mole Fraction of Propyl Acetate for the Mixtures of (Propyl Acetate (1) + n-Pentanol (2)), (Propyl Acetate (1) + 3-Methyl-1-butanol (2)), and (Propyl Acetate (1) + 1-Methyl-1-butanol (2)) at 101.3 kPa n-pentanol
3-methyl-1butanol
NRTL Parameters (τij = Aij + Bij/T) −2.37 4.09 6.04 1.16 1609.79 −1747.38 −2788.96 −227.24 Deviation average absolute deviations y1 0.0119 0.0122 average absolute deviations T/K 0.2396 0.2358 Wilson Parameters (ln Λij = Aij + Bij/T) A12 −10.33 −1.32 A21 4.56 −3.51 B12 3855.45 296.06 B21 −1659.26 1503.33 Deviation average absolute deviations y1 0.0103 0.0127 average absolute deviations T/K 0.2634 0.2288 UNIQUAC Parameters (τij = exp(Aij + Bij/T)) A12 −0.63 0.09 A21 −0.99 −2.34 B12 −98.39 −473.18 B21 619.56 1182.51 Deviation average absolute deviations y1 0.0115 0.0148 average absolute deviations T/K 0.2456 0.2153 A12 A21 B12 B21
a
ACKNOWLEDGMENTS The authors appreciate the useful discussions on molecular simulation calculations from Dr. You Han and Ms. Yujia Wu from the chemical process intensification group of Tianjin University.
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REFERENCES
(1) Mahajan, D.; Vijayaraghavan, P. Selective synthesis of mixed alcohols catalyzed by dissolved base activated highly dispersed slurried iron. Fuel. 1999, 78, 93−100. (2) Matsuzaki, T.; Hanaoka, T.; Takeuchi, K.; Arakawa, H.; Sugi, Y.; Wei, K. Oxygenates from syngas over highly dispersed cobalt catalysts. Catal. Today. 1997, 36, 311−324. (3) Zhao, N.; Xu, R.; Wei, W.; Sun, Y. H. Cu/Mn/ZrO2 catalyst for alcohol synthesis by Fischer-Tropsch modified elements. React. Kinet. Catal. Lett. 2002, 75, 297−304. (4) Luo, H. Y.; Zhang, W.; Zhou, W. H.; Huang, S. Y.; Lin, P. Z.; Ding, Y. J.; Lin, L. W. A study of Rh-Sm-V/SiO2 catalysts for the preparation of C2-oxygenates from syngas. Appl. Catal., A 2001, 214, 161−166. (5) Resa, J. M.; Gonzalez, C.; Landaluce, S. O; Lanz, J. Vapor-liquid equilibrium of binary mixtures containing methanol + propyl acetate, methanol + isopropyl acetate, vinyl acetate + propyl acetate, and vinyl acetate + isopropyl acetate at 101.3 kPa. J. Chem. Eng. Data 2001, 46, 1338−1342. (6) T.R.C. Selected Data on Mixtures. Int. Data Ser., Ser. A 1995, 23, 97−143. (7) Herington, E. F. G. Tests for the consistency of experimental isobaric vapor−liquid equilibrium data. J. Inst. Pet. 1951, 37, 457−470. (8) Renon, H.; Prausnitz, J. M. Local compositions in thermodynamic excess function for liquid mixtures. AIChE J. 1968, 14, 135−144. (9) Wilson, G. M. Vapor−liquid equilibium. XI. A new expression for the excess free energy of mixing. J. Am. Chem. Soc. 1964, 86, 127−130. (10) Abrams, D. S.; Prausnitz, J. M. Statistical thermodynamics of liquid mixtures: A new expression for Gibbs energe of partly or completely miscible System. AIChE J. 1975, 21, 116−128. (11) Grishunin, A. V.; Balashow, M. I.; Patlasov, V. P.; Kissel, V. L.; Serafimov, L. A.; Osnovn, L. A. Org. Sint. Neftekhim. 1976, 5, 109 CA 87: 44876. (12) Resa, J. M.; Gonzalez, C.; Moradillo, B.; Lanz, J. (Vapour + liquid) equilibria for (methanol + butyl acetate), (vinyl acetate + butyl acetate), (methanol + isobutyl acetate), and (vinyl acetate + isobutyl acetate). J. Chem. Thermodyn. 1998, 30, 1207−1219. (13) Lide, D. R. CRC Handbook of Chemistry and Physics, 73rd ed.; CRC Press: Boca Raton, FL, 1992. (14) Riddick, J. A.; Bunger, W. B.; Sakano, T. K. Organic Solvents; Wiley-Interscience: New York, 1986. (15) Project 801-Full Version, Evaluated Process Design Data, Public Release Documentation; Design Institute for Physical Properties (DIPPR); American Institute of Chemical Engineers (AIChE): New York, 2011. (16) Yang, C. S.; Zeng, H.; Yin, X.; Ma, S. Y.; Sun, F. Z.; Li, Y. F.; Li, J. Measurement of (vapor + liquid) equilibrium for the systems {methanol + dimethyl carbonate} and {methanol + dimethyl carbonate + tetramethylammonium bicarbonate} at p = (34.43, 67.74) kPa. J. Chem. Thermodyn. 2012, 53, 158−166. (17) Cai, J. L.; Cui, X. B.; Zhang, Y.; Li, R.; Feng, T. Y. Vapor−liquid equilibrium and liquid−liquid equilibrium of methyl acetate + methanol + 1-ethyl-3-methylimidazolium Acetate. J. Chem. Eng. Data 2011, 56, 282−287. (18) Li, Y. M.; Bai, P.; Zhuang, Q. H. Isobaric vapor−liquid equilibrium for binary system of methanol and acetonitrile. Fluid Phase Equilib. 2013, 34, 42−45. (19) Li, X. M.; Shen, C.; Li, C. X. Effect of alkanolammonium formates ionic liquids on vapour liquid equilibria of binary systems containing water, methanol, and ethanol. J. Chem. Thermodyn. 2012, 53, 167−175.
1-methyl-1butanol 4.44 6.08 −1005.82 −2757.41 0.0110 0.2205 −3.66 −10.41 1712.30 3387.14 0.0106 0.2287 −3.69 −0.41 1041.67 401.68 0.0109 0.2233
NRTL model: α12 = α21 = 0.3.
models can provide relatively accurate predictions of these systems. To understand deeply the reason that results in the better prediction by using the NRTL model, further study using molecular simulation calculations on the molecular interactions is needed.
4. CONCLUSIONS The isobaric VLE data of the binary mixtures {(propyl acetate + n-pentanol), (propyl acetate + 1-methyl-1-butanol), and (propyl acetate + 3-methyl-1-butanol)} have been measured at P = 101.3 kPa. All experimental binary VLE data were tested for thermodynamic consistency using the semiempirical method of Herington. And the NRTL model indicates slightly better results than the other two models in these three binary systems.
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AUTHOR INFORMATION
Corresponding Author
*Tel: +86 022 27890643. E-mail:
[email protected]. com. Funding
The authors are grateful to the financial support from National High-tech R&D Program of China (2012AA062901) and the Special Funds for Major State Basic Research Program of China (2012CB720300). Notes
The authors declare no competing financial interest. E
dx.doi.org/10.1021/je4007184 | J. Chem. Eng. Data XXXX, XXX, XXX−XXX
