Isothermal Vapor–Liquid Equilibrium Data for the Toluene + Methanol

Article pubs.acs.org/jced

Isothermal Vapor−Liquid Equilibrium Data for the Toluene + Methanol + N‑Butylpyridinium Bromide System Alexander V. Kurzin,*,† Andrey N. Evdokimov,† Mariana A. Feofanova,‡ and Nadezhda V. Baranova‡ †

Organic Chemistry Department, Higher School of Technology and Energetics, Saint-Petersburg State University of Industrial Technologies and Design, 4 Ivana Chernykh Street, Saint-Petersburg 198095, Russian Federation ‡ Inorganic and Analytical Chemistry Department, Faculty of Chemical Technology, Tver State University, 35 Sadovy Lane, Tver 170002, Russian Federation ABSTRACT: Salt effect on vapor−liquid equilibrium (VLE) for the toluene + methanol + N-butylpyridinium bromide system at 318.15 K and different salt concentrations (0.300, 0.700, 1.000, 1.200, and 1.500 mol·kg−1) has been determined by headspace gas chromatography. The azeotrope mixture of the toluene + methanol system can be broken by using N-butylpyridinium bromide. The experimental VLE data were correlated well with an electrolyte nonrandom two-liquid model.

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INTRODUCTION The chemical identity of ions has a significant impact on the behavior of a wide range of systems with supramolecular organization: polymer gels, solutions of block copolymers, proteins, and amphiphilic synthetic and biological membranes, etc. For solutions of ionic surfactants, replacement or the nature of the counterion of the salt can lead to background radical rearrangement solution structures that cause transitions in spherical wormlike micelles, the formation of spatial networks, liquid crystalline structures, microemulsions, and phase separation. The above reorganization is often accompanied by changes in the macroscopic characteristics of the system. Pyridinium salts are the sample of organic electrolytes. The most important use of these salts is as surfactants.1 Moreover some pyridinium salts are the room temperature ionic liquids. Organic salts are used in separation processes as well as inorganic salts and ionic liquids. The electrolyte solutions with organic ions continue to represent an important area of theoretical interest as well.2 The studying of thermodynamics of the organic salt solutions is very important because some properties of these systems are the same for the ionic liquids. The toluene + methanol mixture is widely encountered in the pharmaceutical industry. This azeotrope system is formed in the process of the toluene alkylation with methanol. The occurrence of an azeotropic point in the toluene + methanol mixture is a cause of troubles in separating purity alcohol from the mixture by rectification. Several isothermal and isobaric VLE data for the toluene + methanol binary azeotropic system were found as published information.3−8 The toluene + methanol system can be separated by pervaporation,9−14 extractive, and salt distillation15−21 methods. Some VLE data © 2017 American Chemical Society

for mixed solvent toluene + methanol and salt systems were earlier measured. The toluene + methanol system was investigated with lithium bromide, sodium bromide, potassium acetate, calcium chloride, tetrabutylammonium tetraphenylborate, and triphenylbenzylphosphonium chloride.20−24 Only the last two salts can be used as an agent for the isolation of methanol in the toluene + methanol azeotrope mixture.20,21 VLE data, some physical and chemical properties of several binary systems containing ionic liquid based on pyridiniumtype cation, have recently been published.25 Phase transition and decomposition temperatures, heat capacities, and viscosities of pyridinium ionic liquids were earlier studied.26 There is no information about VLE data for the system toluene + methanol + N-butylpyridinium bromide ([Bpy][Br]) in the literature. No data of the effect of this salt in the VLE of azeotrope systems were found in the published information, but some alkylpyridinium based ionic liquids for this purpose were explored.27 This work consists of two aims: to measure the organic salt effect of N-butylpyridinium bromide on the VLE of the toluene + methanol system at 318.15 K and different molalities (0.300, 0.700, 1.000, 1.200, and 1.500 mol·kg−1) with the help of headspace gas chromatography and to determine the possibility of a breaking or disappearing azeotrope point in the toluene + methanol system when organic salt is added. The data presented in this work are a part of our study on pyridinium salts which are not room temperature ionic liquids Received: March 31, 2016 Accepted: January 18, 2017 Published: February 1, 2017 889

DOI: 10.1021/acs.jced.6b00279 J. Chem. Eng. Data 2017, 62, 889−892

Journal of Chemical & Engineering Data

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Table 1. Chemical Sample Table

a

chem name

source

initial mole fraction purity

purification method

final mole fraction purity

anal method

methanol toluene 1-butylpyridinium bromide

Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich

0.998 0.995 0.990

store above the molecular sieves store above the molecular sieves vacuum drying

0.998 0.996 b

GCa GCa melting point

Gas−liquid chromatography. bNot measured.

to determine the organic salt effect on VLE in mixed solvent systems with these types of electrolytes.28 Different types of semiempirical predictive and correlative models found on the group contribution concept or local composition have been offered for calculation of VLE in the mixed solvent + electrolyte systems. The experimental VLE data introduced in this work were correlated by the electrolyte nonrandom two-liquid (NRTL) model of Mock et al.29 This model is usually applied in the mixtures with ionic liquids or salts having large organic ions.20,21,30−33 We earlier used this model for correlation of VLE data for the N-butylpyridinium hexafluorophosphate + acetone + methanol system.28

Table 2. Experimental Vapor−Liquid Equilibrium Data for the System Methanol (1) + Toluene (2) + N-Butylpyridinium Bromide (3) without Vapor Pressure Measurement, Vapor Mole Fraction of Methanol (y1) as a Function of Liquid Mole Fraction of Methanol on a SaltFree Basis (x′1), and Salt Molality (m3) at Temperature T/K = 318.15a x′1

y1

x′1

y1

x′1

m3/(mol·kg−1) = 0.000 m3/(mol·kg−1) = 0.300 0.025 0.580 0.025 0.582 0.082 0.728 0.082 0.733 0.101 0.743 0.101 0.749 0.183 0.771 0.183 0.780 0.202 0.780 0.202 0.790 0.251 0.790 0.251 0.802 0.303 0.792 0.303 0.806 0.394 0.795 0.394 0.813 0.450 0.801 0.450 0.821 0.498 0.807 0.498 0.829 0.558 0.809 0.558 0.833 0.601 0.810 0.601 0.836 0.625 0.811 0.625 0.838 0.702 0.822 0.702 0.850 0.764 0.833 0.764 0.862 0.867 0.867 0.867 0.893 0.903 0.900 0.903 0.920 0.960 0.935 0.960 0.949 m3/(mol·kg−1) = 1.000 m3/(mol·kg−1) = 1.200 0.025 0.584 0.025 0.585 0.082 0.737 0.082 0.738 0.101 0.753 0.101 0.755 0.183 0.788 0.183 0.790 0.202 0.798 0.202 0.800 0.251 0.811 0.251 0.814 0.303 0.817 0.303 0.820 0.394 0.827 0.394 0.831 0.450 0.837 0.450 0.841 0.498 0.845 0.498 0.850 0.558 0.852 0.558 0.857 0.601 0.856 0.601 0.861 0.625 0.858 0.625 0.864 0.702 0.872 0.702 0.878 0.764 0.884 0.764 0.890 0.867 0.913 0.867 0.919 0.903 0.936 0.903 0.940 0.960 0.960 0.960 0.963

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EXPERIMENTAL SECTION Materials. Methanol (w ≥ 99.8%, Sigma-Aldrich) and toluene (w ≥ 99.5%, Sigma-Aldrich) were stored above the zeolites (molecular sieves, 3A). Gas chromatography was used for determination of solvents purities. 1-Butylpyridinium bromide was obtained from Sigma-Aldrich (w ≥ 99.0%) and dried before experiments in a vacuum oven at 75−80 °C. Melting points of the dried salt were in the range of 104−106 °C (by melting point meter M5000 (A. KRUSS Optronic GmbH), u(mp) = 0.4 °C; Table 1). Procedure. The binary toluene + methanol mixtures and ternary toluene + methanol + N-butylpyridinium bromide mixtures were made gravimetrically with an analytical balance (Ohaus Explorer Pro balance) with an uncertainty of 0.1 mg. In each experimental point, 8 cm3 of mixture was batched up into the 30 cm3 heated sample vial. After the vial was closed by means of a special lid equipped with a washer, it was brought to the required temperature in a thermostatic cell. The mixture was continuously agitated for 6 h. The uncertainty of the measured temperature was 0.01 K. The combined standard uncertainties of the measured mole fraction in the vapor phase and mole fraction of solvents (on a salt-free basis) were 0.001. Analysis Method. Each solvent mole fraction (on a saltfree basis) in the vapor (yi) phase was tested by headspace gas chromatography.34 This method has been successfully used for isothermal studying of the ternary systems mixed solvent + electrolyte without vapor pressure measurement. To analyze the vapor phase composition, the vapor was automatically withdrawn using a PerkinElmer F45 GLC vapor analyzer and analyzed by a F22 gas chromatograph. The chromatographic column (3 m × 0.3 mm) was packed with Porapak-Q. The injector and chamber temperatures were 160 and 120 °C, respectively. The carrier gas was argon (purity = 99.9%) flowing at 0.5 cm3·s−1. The gas chromatograph was calibrated using a mixture of methanol and toluene that were prepared gravimetrically by using an analytical balance with an uncertainty of ±0.1 mg. Because of negligible amounts in the vapor phase (small vapor volume, moderate pressure), it was reasonable to assume that the liquid phase composition is the same as the feed composition. To prepare the calibration samples for the vapor phase, various methanol and toluene

y1

m3/(mol·kg−1) = 0.700 0.025 0.583 0.082 0.735 0.101 0.751 0.183 0.785 0.202 0.794 0.251 0.807 0.303 0.812 0.394 0.821 0.450 0.830 0.498 0.838 0.558 0.844 0.601 0.847 0.625 0.849 0.702 0.862 0.764 0.874 0.867 0.904 0.903 0.929 0.960 0.955 m3/(mol·kg−1) = 1.500 0.025 0.586 0.082 0.740 0.101 0.756 0.183 0.793 0.202 0.803 0.251 0.818 0.303 0.825 0.394 0.837 0.450 0.848 0.498 0.857 0.558 0,865 0.601 0.870 0.625 0.873 0.702 0.887 0.764 0.900 0.867 0.928 0.903 0.947 0.960 0.968

u(T) = 0.01 K, u(x) = u(y) = 0.004, u(m) = 0.001 mol·kg−1, and solvent is a methanol + toluene mixture. a

mixtures were completely evaporated in a 1000 ± 0.1 cm3 vessel and injected. To obtain the calibration equation, the required mass fractions and area fractions were correlated with a third-order polynomial by a least-squares method (mean deviation = 0.1%). The experimental procedure is also described in detail in our past work.30 890

DOI: 10.1021/acs.jced.6b00279 J. Chem. Eng. Data 2017, 62, 889−892

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RESULTS AND DISCUSSION

Gij = exp( −αijτij)

Before studying the ternary system, we measured the VLE data for the binary toluene + methanol system. Our data are listed in Table 2. For this system, there are many isothermal and isobaric VLE data that were earlier published in the literature.3−8 We compared our measured data with published ones.6 The similar agreement is presented in Figure 1.

(2)

All model parameters used for the studied system are presented in Table 4. Table 4. Energy Parameters (Δgij and Δgji) and Nonrandomness Factors (αij) for the Electrolyte NRTL Modela

a

i

j

αij

Δgij/(J·mol−1)

Δgji/(J·mol−1)

methanol methanol toluene

toluene [Bpy][Br] [Bpy][Br]

0.4749 0.3 0.2

3380.8926 1588.3 18305.5

4666.501 −11254.7 −7213.8

Reference 29.

Mean absolute deviation and standard deviation between experimental and calculated values of the vapor phase mole fractions are 0.007 and 0.006, respectively.

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CONCLUSION The VLE data of the toluene + methanol + N-butylpyridinium bromide system have been investigated at 318.15 K at five different salt concentrations (0.300, 0.700, 1.000, 1.200, and 1.500 mol·kg−1). The headspace gas chromatography method without vapor pressure measurement was used. N-Butylpyridinium bromide can be used in the salt distillation process for breaking the azeotrope in the toluene + methanol system. For correlation of VLE data the electrolyte NRTL model was used with the required accuracy.

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Figure 1. Vapor mole fraction (y1) of methanol in the methanol (1) + toluene (2) + N-butylpyridinium bromide (3) system at 318.15 K and different salt concentrations (m3): ⧫, no salt (this work); ◊, no salt (Nagata6); ○, m3 = 0.300 mol·kg−1; ●, m3 = 0.700 mol·kg−1; ×, m3 = 1.000 mol·kg−1; +, m3 = 1.200 mol·kg−1; ⊗, m3 = 1.500 mol·kg−1. Liquid mole fraction of methanol (x′1) is on a salt-free basis. The solid line is a line to identify the azeotropic behavior.

Corresponding Author

*E-mail: [email protected]. ORCID

Alexander V. Kurzin: 0000-0001-6108-041X Notes

The experimental VLE data for the ternary system toluene + methanol + N-butylpyridinium bromide are presented in Table 2 and Figure 1. The N-butylpyridinium bromide additive to the toluene + methanol system increases the methanol mole fraction in the vapor phase. We found that with use of a salt concentration above 1.200 mol·kg−1 the azeotrope disappears in the studied system. As shown in Table 3 N-butylpyridinium

The authors declare no competing financial interest.

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m3/(mol·kg−1)

ref

[Bpy][Br] tetrabutylammonium tetraphenylborate triphenylbenzylphosphonium chloride

1.200 0.3 0.1

this work 21 20

bromide can be used as an entrainer for the elimination of azeotrope in the methanol + toluene system. For describing VLE behavior the experimental data were correlated with the electrolyte NRTL model of Mock et al.29 Only two types of nine model parameters for the ternary mixed solvent + salt system are required: three nonrandomness factors (αij) and six energy parameters (Δgij, Δgji). The parameters Gij and τij are calculated by29 τij = Δgij /RT

REFERENCES

(1) Jo, T. S. Synthesis and Characterizations of Pyridinium Salts Including Poly(pyridinium salt)s and Their Applications. Ph.D. Dissertation, University of Nevada: Las Vegas, NV, USA, 2012. (2) Mischenko, K. P.; Poltoratskiy, G. M. Thermodynamics and Structure of the Aqueous and Nonaqueous Electrolyte Solutions, 2nd ed.; Khimiya, Leningradskoe Otdelenije: Leningrad, 1976. (3) Lu, B. C.-Y. Vapor−Liquid Equilibrium Data for Systems Methanol−Toluene and n-Propanol−Toluene. Can. J. Technol. 1957, 34, 468−472. (4) Burke, D. E.; Williams, G. C.; Plank, C. A. Vapor−Liquid Equilibria for the Methanol − Toluene System. J. Chem. Eng. Data 1964, 9, 212−214. (5) Ocon, J. G.; Tojo, G. B.; Espada, L. Vapour−Liquid Equilibrium. X. Methanol − Toluene System. An. Quim. 1969, 65, 641−648. (6) Nagata, I. Isothermal (Vapour−Liquid) Equilibria of (Methanol + Toluene) and of (Methanol + Acetonitrile + Toluene). J. Chem. Thermodyn. 1988, 20, 467−471. (7) Oh, J.-H.; Han, K.-J.; Won, D.-B.; Park, S.-J. Vapor−Liquid Equilibria for the Ternary Systems of Methyl tert-Butyl Ether + Methanol + Benzene and Methyl tert-Butyl Ether + Methanol + Toluene and Constituent Binary Systems at 313.15 K. Fluid Phase Equilib. 2003, 209, 215−228. (8) Goral, M.; Skrzecz, A.; Bok, A.; Maczynski, A.; Oracz, P. Recommended Vapor−Liquid Equilibrium Data. Part 3. Binary Alkanol − Aromatic Hydrocarbon Systems. J. Phys. Chem. Ref. Data 2004, 33, 959−997.

Table 3. Efficiency of Salts for Azeotrope Elimination in the Methanol (1) + Toluene (2) + Salt (3) System, Salt Molality (m3) salt

AUTHOR INFORMATION

(1) 891

DOI: 10.1021/acs.jced.6b00279 J. Chem. Eng. Data 2017, 62, 889−892

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(27) Dhanalakshmi, J.; Sai, P. S. T.; Balakrishnan, A. R. Study of Ionic Liquids as Entrainers for the Separation of Methyl Acetate − Methanol and Ethyl Acetate − Ethanol Systems Using the COSMO-RS Model. Ind. Eng. Chem. Res. 2013, 52, 16396−16405. (28) Kurzin, A. V.; Evdokimov, A. N.; Antipina, V. B.; Pavlova, O. S. Liquid−Vapor Equilibrium in the System Acetone − Methanol − NButylpyridinium Hexafluorophosphate. Russ. J. Appl. Chem. 2007, 80, 2049−2050. (29) Mock, B.; Evans, L. B.; Chen, C.-C. Thermodynamic Representation of Phase Equilibria of Mixed-Solvent Electrolyte Systems. AIChE J. 1986, 32, 1655−1664. (30) Kurzin, A. V.; Evdokimov, A. N.; Antipina, V. B.; Feofanova, M. A. Vapor−Liquid Equilibrium Data for the Methanol + Benzene + Tetraphenylphosphonium Chloride System. J. Chem. Eng. Data 2016, 61, 1131−1135. (31) Yang, C.; Yin, X.; Ma, S. Organic Salt Effect of Tetramethylammonium Bicarbonate on the Vapor−Liquid Equilibrium of the Dimethyl Carbonate + Methanol System. J. Chem. Eng. Data 2012, 57, 66−71. (32) Orchilles, O. V.; Miguel, P. J.; Vercher, E.; Martinez-Andreu, A. Ionic Liquids as Entrainers in Extractive Distillation: Isobaric Vapor− Liquid Equilibria for Acetone + Methanol + 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate. J. Chem. Eng. Data 2007, 52, 141− 147. (33) Orchilles, O. V.; Miguel, P. J.; González-Alfaro, V.; Vercher, E.; Martinez-Andreu, A. 1-Ethyl-3-methylimidazolium Dicyanamide as a Very Efficient Entrainer for the Extractive Distillation of the Acetone + Methanol System. J. Chem. Eng. Data 2012, 57, 394−399. (34) Takamatsu, H.; Ohe, S. Measurement of the Effect of Salt on Vapor−Liquid Equilibria by Using Headspace Gas Chromatography. J. Chem. Eng. Data 2003, 48, 277−279.

(9) Mandal, S.; Pangarkar, V. G. Separation of Methanol−Benzene and Methanol−Toluene Mixtures by Pervaporation: Effects of Thermodynamics and Structural Phenomenon. J. Membr. Sci. 2002, 201, 175−190. (10) Pal, S. M.; Pangarkar, V. G. Acrylonitrile-Based Copolymer Membranes for the Separation of Methanol from a Methanol − Toluene Mixture through Pervaporation. J. Appl. Polym. Sci. 2005, 96, 243−252. (11) Singha, N. R.; Kuila, S. B.; Das, P.; Ray, S. K. Separation of Toluene − Methanol Mixtures by Pervaporation Using Crosslink IPN Membranes. Chem. Eng. Process. 2009, 48, 1560−1565. (12) Singha, N. R.; Ray, S. K. Separation of Toluene − Methanol Mixtures by Pervaporation Using Semi-IPN Polymer Membranes. Sep. Sci. Technol. 2010, 45, 2298−2307. (13) Lue, S. J.; Ou, J. S.; Kuo, C. H.; Chen, H. Y.; Yang, T.-H. Pervaporative Separation of Azeotropic Methanol/Toluene Mixtures in Polyurethane − Poly(dimethylsiloxane) (PU−PDMS) Blend Membranes: Correlation with Sorption and Diffusion Behaviors in a Binary Solution System. J. Membr. Sci. 2010, 347, 108−115. (14) Garg, P.; Singh, R. P.; Choudhary, V. Selective Polydimethylsiloxane/Polyimide Blended IPN Pervaporation Membrane for Methanol/Toluene Azeotrope Separation. Sep. Purif. Technol. 2011, 76, 407−418. (15) Huang, S.; Li, W.; Li, Y.; Ma, J.; Shen, C.; Xu, C. Process Assessment of Distillation Using Intermediate Entrainer: Conventional Sequences to the Corresponding Dividing-Wall Columns. Ind. Eng. Chem. Res. 2016, 55, 1655−1666. (16) Ma, J.; Li, W.; Ni, C.; Li, Y.; Huang, S.; Shen, C.; Xu, C. Investigation of Distillation Systems Using Heavy or Intermediate Entrainers for Separating Toluene − Methanol: Process Economics and Control. J. Chem. Technol. Biotechnol. 2016, 91, 2111−2124. (17) Tang, K.; Bai, P.; Zhang, J.; Huo, Y. Separation of Methanol− Toluene Azeotropic Mixture by Extractive Distillation. Asian J. Chem. 2013, 25, 321−326. (18) Modla, G. Energy Saving Methods for the Separation of a Minimum Boiling Point Azeotrope Using an Intermediate Entrainer. Energy 2013, 50, 103−109. (19) Yang, D.; Du, P.; Ye, M.; Gao, X. Separation of Methanol − Toluene by Combined Process of Extraction with Salt and Distillation. Huaxue Gongcheng (Chem. Eng. (China)) 2014, 42 (N5), 31−34. (20) Kurzin, A. V.; Evdokimov, A. N.; Antipina, V. B.; Pavlova, O. S.; Gusev, V. E. Isothermal Vapor−Liquid Equilibrium Data for the System Methanol + Toluene + Triphenylbenzylphosphonium Chloride. J. Chem. Eng. Data 2007, 52, 2174−2176. (21) Kurzin, A. V.; Evdokimov, A. N.; Antipina, V. B.; Pavlova, O. S. Vapor−Liquid Equilibrium Data for the System Methanol + Toluene + Tetrabutylammonium Tetraphenylborate. J. Chem. Eng. Data 2008, 53, 1411−1413. (22) Aneke, L. E. Salt Effect in Vapor−Liquid Equilibrium Methanol− Toluene System. Ph.D. Dissertation, University of Rhode Island: Kingston, RI, USA, 1966. (23) Aneke, L. E. Vapour−Liquid Equilibria of the Methanol + Toluene System Saturated with Sodium Bromide. Indian Chem. Eng. 1980, 22, 27−31. (24) Rath, P.; Naik, S. C. Effect of Salts on Vapour−Liquid Equilibria of the System Methanol−Toluene. J. Inst. Eng. (India), Chem. Eng. Div. 1990, 70, 82−85. (25) Bahadur, I.; Pal, A.; Gmehling, J.; Hector, T.; Tumba, K.; Singh, S.; Ebenso, E. E. (Vapour + Liquid) Equilibria, (VLE) Excess Molar Enthalpies and Infinite Dilution Activity Coefficients of Selected Binary Systems Involving n-Hexyl Pyridinium Bis(trifluoromethylsulphonyl)imide Ionic Liquid: Experimental and Predictions Using Modified UNIFAC (Dortmund). J. Chem. Thermodyn. 2015, 90, 92−99. (26) Crosthwaite, J. M.; Muldoon, M. J.; Dixon, J. K.; Anderson, J. L.; Brennecke, J. F. Phase Transition and Decomposition Temperatures, Heat Capacities and Viscosities of Pyridinium Ionic Liquids. J. Chem. Thermodyn. 2005, 37, 559−568. 892

DOI: 10.1021/acs.jced.6b00279 J. Chem. Eng. Data 2017, 62, 889−892