Phase Equilibrium Investigation on 2-Phenylethanol in Binary and

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B: Biophysics; Physical Chemistry of Biological Systems and Biomolecules

Phase Equilibrium Investigation on 2-Phenylethanol (PEA) in Binary and Ternary Systems. The Influence of High Pressure on Density and SLE Urszula Maria Domanska, Marek Królikowski, Michal Wlazlo, and Mikolaj Wieckowski J. Phys. Chem. B, Just Accepted Manuscript • DOI: 10.1021/acs.jpcb.8b02500 • Publication Date (Web): 15 May 2018 Downloaded from http://pubs.acs.org on May 16, 2018

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The Journal of Physical Chemistry

J. Phys. Chem.B

Phase Equilibrium Investigation on 2-Phenylethanol (PEA) in Binary and Ternary Systems. The Influence of High Pressure on Density and SLE Urszula Domańska,‡†* Marek Królikowski,†† Michał Wlazło† and Mikołaj Więckowski†

Received: 14 March 2018

†Dr. Eng. M. Królikowski, Dr.Eng. M. Wlazło, student M. Więckowski, Department of Physical Chemistry, Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw (Poland). ‡

Prof. Dr. hab. U. Domańska, Industrial Chemistry Research Institute, Rydygiera 8, 01-793

Warsaw (Poland). †

Prof. Dr. hab. U. Domańska, Dr. Eng. M. Królikowski, Thermodynamic Research Unit,

School of Engineering, University of KwaZulu-Natal, Howard College Campus, King George V Avenue, Durban 4041 (South Africa).

* Corresponding author: Prof. Dr. hab. U. Domańska, [email protected]

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Abstract: Ionic liquids (ILs) are important new solvents proposed for applications in different separation processes. Herein, an idea of the possible use of high pressure in general strategy of production of 2-phenylethanol (PEA) is discussed. In this work we present the influence of pressure

on

the

density

in

binary

systems

of

{1-hexyl-1-methylpyrrolidynium

bis{(trifluoromethyl)sulfonyl}imide, [HMPYR][NTf2], or 1-dodecyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide, [DoMIM][NTf2] + 2-phenylethanol (PEA)} in a wide range of temperature (298.15-348.15) K and pressure (0.1-40) MPa. The density at ambient and high pressures are measured to present the physicochemical properties of the ILs used in the process of separation of PEA from aqueous phase. The Tait equation was used for the correlation

of

density

of

one

component

and

two-component

systems

as

a function of mole fraction, temperature, and pressure. The influence of pressure is not significant. These systems exhibit mainly negative molar excess volumes, V E . The solidliquid phase equilibrium (SLE) of [DoMIM][NTf2] in PEA at atmospheric pressure was measured and compared to the SLE high-pressure results. Additionally, the ternary liquidliquid phase equilibrium (LLE) at ambient pressure in the {[DoMIM][NTf2] (1) + PEA (2) + water (3)} at temperature T = 308.15 K was investigated. The solubility of water in the [DoMIM][NTf2] is quite high in comparison with measured by us earlier ILs (x3 = 0.403) at T = 308.15 K, which results in not very successful average selectivity of extraction of PEA from the aqueous phase. The [DoMIM][NTf2] have shown strong interaction with PEA without immiscibility region. The ternary system revealed Treybal’s type phase equilibrium in which two partially miscible binaries ([DoMIM][NTf2] + water) and (PEA + water) exists. From the results of LLE in ternary system the selectivity and the solute distribution ratio of separation water/PEA were calculated and compared to the results obtained for the measured earlier by us ILs. The popular NRTL model was used to correlate the experimental tie-lines in ternary

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LLE. These results may help in a new technological project of "in situ" extraction of PEA from aqueous phase during the biosynthesis.

■ INTRODUCTION

2-Phenylethanol (PEA) is an alcohol of a specific floral odor that occurs widely in nature in a many flowers such as rose, hyacinth, geranium and many others.1,2 It is, therefore, a common ingredient used in perfumery, food, and pharmacy. It is responsible for aroma component of Muscat wine and in some cigarettes. In biology, it is of interest due to its antimicrobial properties. Natural PEA known for the best rose-like flavor can be extracted from the essential oils of certain flowers, between them the most popular are roses. The extraction process is very popular but also very expensive. For many years, according to the USA and European legislations, the use of cheap chemically synthesized PEA is restricted to use in food, beverages, and cosmetics.3,4 The most efficient biotechnological approach is the whole-cell microbial transformation of

L-phenylalanine

to PEA with Saccharomyces

cerevisiae yeast in the aqueous phase.4-8 The biotechnological production of PEA needs in situ product removal from the aqueous phase.4-8Among the different techniques proposed, the liquid-liquid two-phase extraction is inexpensive and low energy consuming process. The new technology expect a suitable organic solvent (entrainer), which may be used for the extraction. The selection of entrainer is important in this technology because cannot be toxic to the yeast and has to reveal high selectivity in product recovery. Many solvents were already described in the literature, such as oleic acid, alcohols, esters, polypropylene glycol 1200 and ionic liquids (ILs).1 Recently, intensive investigations were reported using IL as extractive solvents.9-18 However, ILs are expensive solvents and in many cases are not attractive for the

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biotransformation, the enhance of PEA production in a biphasic system in comparison with traditional organic solvents was observed.9,17,19 Different ILs were investigated in the ternary liquid-liquid phase equilibrium (LLE) {IL + PEA + water} systems. The imidazolium-, isoquinolinium-, pyrrolidinium-, piperidinium-, ammonium-, morpholinium-, sulfonium-based ILs with different anions such as

bis{(trifluomethyl)sulfonyl}imide

[NTf2]-,

tetracyanoborate

[TCB]-,

and

bis(fluorosulfonyl)imide (FSI–).10-18 The best selectivities of PEA extraction (S23) and solute distribution ratios (β2) were observed in these ternary systems for N-octylisoquinolinium bis(trifluoromethylsulfonyl)imide, [C8iQuin][NTf2],11 for N-methyl-N-trioctylammonium bis{(trifluoromethyl)sulfonyl}imide,

[N1888][NTf2]13 and for N-triethyl-N-octylammonium

bis{(trifluoromethyl)sulfonyl}imide, [N2228][NTf2].13 In general, the tetracyanoborate-based ILs and bis(fluorosulfonyl)imide-based ILs were less effective in the extraction processes. In this work we continue our studies on physic-chemical properties of the IL and phase equilibria in binary ([DoMIM][NTf2] + PEA) and in ternary systems {[DoMIM][NTf2] (1) + PEA (2) + water (3)} with the aim of determining the influence of pressure on phase equilibria and density. In this work, the following ILs are proposed: 1-dodecyl-1methylimidazolium bis{(trifluoromethyl)sulfonyl}imide, [DoMIM][NTf2] and

1-hexyl-1-

methylpyrrolidinium bis{(trifluoromethyl)sulfonyl}imide, [HMPYR][NTf2]. It is widely known, that the chemical structure of the IL cation is responsible of the interaction in the solution and the extraction potential of the IL. The [DoMIM][NTf2] was successfully used by us in the separation of butan-1-ol from the aqueous phase.20 Bio-fuels are proposed to be produced and extracted from biomass after the fermentation process. The [DoMIM][NTf2] has shown very attractive selectivity (2.75) in butan-1-ol/water separation process in comparison with all published ILs in gamma infinity measurements.20 Additionally, because of the quite high melting temperature (292.4 K) it is possible to make the measurements of high-pressure 4


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solid-liquid equilibrium (SLE) for this IL.20 The [HMPYR][NTf2] has shown the largest concentration of PEA in organic phase after 48 h of bioprocess (16.46 ± 0.23 g·dm-3) in comparison with selected ILs used.17 This work addresses the study of the influence of pressure on mutual solubilities between ILs and PEA and density attempting to relate them to the chemical structure of the cation of the IL.

■ EXPERIMENTAL SECTION

Materials. The [HMPYR][NTf2] (CAS: 380497-19-8) IL was synthesized in our laboratory12 with purity >0.980 mass fraction. The [DoMIM][NTf2] (CAS: 404001-48-5) IL was supplied by IoLiTec with purity >0.980 mass fraction. Table S1 in the Supporting Information (SI) presents the properties of ILs used in this work. Both ILs were degassed during 24 h under low pressure at temperature T = 350 K to remove volatile impurities and trace water. PEA (CAS: 60-12-8) was obtained from Merck. The activated molecular sieves of type 4Å (Union Carbide) were used for dehydration of PEA. Water used in ternary LLE measurements was doubly distilled and degassed (PURE LAB Option Q Elga Water System). The Milipore purification system was used for water used. The density of water was 0.9984 g·cm-3 at T = 293.15 K and conductivity, κ < 0.05µS·cm-1 at T = 293.15 K. The properties of solvents used are listed in Table S2 in the SM. Water content. The Karl-Fischer titration technique (method TitroLine KF) was used for the control of water content. The solid sample of [DoMIM][NTf2] was dissolved in methanol and titrated in steps of 0.0025 cm3. The [HMPYR][NTf2], PEA and solvents were titrated in steps of 0.0025 cm3 without methanol The uncertainty in the water content is u(w.c.)= ± 10· 10-

5



6

for the 3 cm3 IL sample injected. The water contents in ILs used are listed in Table S1 and

other solvents in Table S2 in the SI. Density measurements. For the measurement of the densities of ILs the typical Anton Paar DMA 4500M, Graz, Austria vibrating-tube densimeter was used at ambient pressure and at different temperatures. Two integrated Pt 100 platinum thermometers were used for the controlling temperature. The precision of the temperature measurements was internally (T± 0.01 K). The apparatus is precise to within 1⋅10-5kg·m-3. The uncertainty of the density measurements is assumed as u(ρ) = ±1.4⋅10-3kg·m-3. The calibration of the apparatus was made using doubly distilled and degassed water (PURE LAB Option Q Elga Water System), specially purified benzene (CHEMIPAN, Poland 0.999) and dried air at ambient pressure. Density measurements at high pressure. The Anton PaarDMA HPM,Graz, Austriadensitometer for high pressure and temperatures with Julabo MA, Seelbach, Germany thermostat were used for high-pressure density measurements (see Fig. 1). The density was determined by measuring of oscillations of U-shaped tube with accuracy u(τ) = 1ns at the temperature set with precision u(T) = 0.01 K. The measurements were carried out by introducing a degassed sample into the duct of apparatus and compressing it to the expected pressure. The pressure was measured by the WIKA HP-2 Pressure Transmitter, Poland for ultra-high-pressure measurement applications with accuracy u(p) = 0.1MPa for the range between 20 and 40 MPa and u(p) = 0.01MPa for lower values. Afterwards, the system was thermostated until the indications of pressure, temperature and oscillations were determined. Values of density in a wide range of pressures and temperatures were determined using the polynomial equation as a function of pressure, temperature and oscillation.

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ρ = AA + AB ∙ d + AC ∙ d + AD ∙ d + AE ∙ d + AF + AG ∙ d + AH ∙ d + AI ∙

d + AJ ∙ d ∙ dτ + AK ∙ dτ

(1)

where dT is temperature, dp - pressure and dτ- period, symbols AA to AK stand for polynomial coefficients. Coefficients (AA to AK) of polynomial were calculated with the help of supplied Excel tool by the manufacturer - Anton Paar. To determined the polynomial coefficient, performed a number of measurements using a product of the "DMA HPM Wide Range" with different samples of pure organic solvents at different temperatures and pressures. The measuring points were taken with standards of density and have been selected so that they were equally distributed in the density, temperature and pressure ranges of interest. Additional measuring points with standards of known density were used to check the accuracy of the polynomial formula. Calibration of densitometer was performed with use of common substances of wellknown densities at the T, p considered: water,21 dichloromethane,22 toluene,23 n-octane,23 and octan-1-ol.24 Adjustment was performed in a wide range of temperature (290-350 K) and below 40MPa with average uncertainty of density u(ρ) = 0.19 kg·m-3. In case of mixtures, the quantities of compounds were defined using an analytical balance and then mixed in an air tight vessel for one hour to homogenize the composition of the sample. Firstly the density at ambient pressure was investigated, then the same sample was used in high-pressure analysis.

7



Figure 1. Schematic diagram of the apparatus (P- pressure gauge).

Procedure of SLE in binary system. The well known synthetic method was used for the measurements of solubility of [DoMIM][NTf2] in the saturated solution.11,15 The sample of (IL + PEA) was prepared by weighing. The solution was heated very slowly (< 2 K·h−1) with continuous stirring inside a Pyrex glass cell placed in a thermostat. The temperature of crystal disappearance was detected visually, within an increasing temperature. Temperature was controlled with an electronic thermometer P 750 (DOSTMANN electronic GmbH). The uncertainties of the measurements were: u(T) = ± 0.2 K, u(p) = ±0.1 kPa, u(x) = ±0.0005 in the mole fraction. Procedure in SLE high pressure. The high pressure piston-cylinder device was described in our previous works.25-27 The hand hydraulic press was used to move the mobile piston. The temperature was controlled by a thermocouple connected with the water thermostat Julabo MA, Seelbach, Germany. The Pt-resistance thermometer Delta HD 9215 (Poland) was used for the temperature measurements. The uncertainties of the temperature and pressure control were: u(T) = ±0.1 K, u(p) = ±2% (up to 1.0 GPa). The volume-pressure curve was observed with an increasing pressure at constant temperature. The initiation of

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freezing was noticed at a slightly higher pressure than the equilibrium value of this phase transition on the (liquid + solid) phase transitions curve. The point of discontinuity on the curve, observed as an “overpressure” effect (the intersection between the lines of the one- and two-phase regions) was taken as an phase change transition point. Thus the equilibrium point was assumed to be the first on the liquidus line.25-27 The measurements were repeated few times and the results are the average of these measurements. Procedure in ternary systems. The experimental LLE tie-lines were developed in one system{[DoMIM][NTf2] (1) + PEA (2) + water (3)} at constant temperature and pressure T = 308.15 K and p = 0.1 MPa. The samples were stirred for 6 h in a jacketed vessel of the volume 10 cm3. The vessel was connected to a thermostatic water bath (LAUDA Alpha), Germany. After the next 12 h without mixing the samples of about 0.1-0.3·10-3 cm3 were taken from two phases and were analyzed with GC (PerkinElmer Clarus 580 GC equipped with auto-sampler and FID and TCD detectors). An acetone (1.0 cm3) was added to the samples to avoid phase splitting and to maintain a homogeneous mixture. Propan-1-ol was used as internal standard for the GC-analysis. The detection was made only for PEA and water. The third component, the IL has now vapor pressure and the concentration was determined by subtracting the mole fractions of the two other components from one. The protection of the capillary column of the chromatograph was made with a pre-column in a case of the leak of non-volatile IL from the glass wool in the liner. The concentration of components in mole fractions were obtained with the GC-Solution software as an average of . three injections. The uncertainty of the concentration was u(x1) = 0.003. The operational conditions of the GC are listed in Table S3 in the SI.

■ RESULTS AND DISCUSSION

9



The influence of temperature and pressure on density. The densities, ρ measured as a function of temperature and pressure are presented in Table S4 in the SI. The typical dependencies of densities with temperature is observed. The density of two ILs decreases with an increase of temperature. The densities of ILs ranging in values from 1335.7 kg·m-3 at T = 298.15K ([HMPYR][NTf2]) to 1293.3 kg·m-3 at T = 348.15 K and from 1242.3 kg·m-3 at T = 298.15K ([DoMIM][NTf2]) to 1198.9 kg·m-3 at T = 348.15 K ([DoMIM][NTf2]) at p = 0.1 MPa. The density of PEA ranging in values from 1018.0 kg·m-3 at T = 298.15K to 979.2 kg·m-3 at T = 348.15 K at p = 0.1 MPa. At all temperatures densities of the ILs increases in order: [DoMIM][NTf2] < [HMPYR][NTf2]. The influence of pressure is not significant. The densities of ILs ranging in values from 1335.7 kg·m-3 at p = 0.1 MPa ([HMPYR][NTf2]) to 1362.0 kg·m-3 at p = 40.0 MPa and from 1242.3 kg·m-3 at p = 0.1 MPa ([DoMIM][NTf2]) to 1268.6 kg·m-3 at p = 40.0 MPa ([DoMIM][NTf2]) at T = 298.15K. The density of PEA ranging in values from 1018.0 kg·m-3 at p = 0.1 MPa to 1036.7 kg·m-3 at p = 40.0 MPa at T = 298.15K. Some of the ILs data were already published at p = 0.1 MPa and the results are compared to each other in Table 1.12,20,28 Our new data for [HMPYR][NTf2] agreed to the published earlier28 and are slightly different to published by our data.12 Larger discrepancies are observed for [DoMIM][NTf2], which was supplied by the same producer, was measured with the same apparatus in the same laboratory.20 The only reason might be the contamination of water, which is always carefully controlled but has the strong influence on density. In this work density was measured with two apparatus, DMA 4500M and DMA HPM at p = 0.1 MPa for the whole temperature range (298.15-348.15) K. The results presented in Fig. S1 in the SI for binary systems of two ILs with PEA evidently confirm the data obtained in this work by two different methods.

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Table 1. Experimental Density ρ, for the Binary Systems {IL (1) + PEA (2)} for Different Mole Fractions x1, as a Function of Temperature T at pressure p = 101 kPaa

ρ/(kg·m-3) at T/(K)

x1

298.15

308.15 318.15 328.15 338.15 [HMPYR][NTf2] 0.0000 1017.4 1009.9 1002.3 994.6 986.7 0.2000 1152.5 1144.5 1136.4 1128.4 1120.3 0.4000 1228.4 1220.1 1211.9 1203.6 1195.4 0.6001 1276.8 1268.4 1260.1 1251.8 1243.5 0.8000 1310.5 1302.0 1293.6 1285.3 1277.0 1.0000 1335.3a 1326.8a 1318.3a 1309.9a 1301.6a 1.0000 1335.3b 1326.8b 1318.3b 1309.9b 1301.4b 1.0000 1332.0c 1323.4c 1314.9c 1306.4c 1297.9c [DoMIM][NTf2] 0.2000 1125.4 1117.4 1109.4 1101.4 1093.3 0.4000 1177.2 1168.9 1160.7 1152.5 1144.4 0.6000 1207.2 1198.8 1190.5 1182.3 1174.0 0.8000 1227.3 1218.8 1210.4 1202.1 1193.8 1.0000 1242.9d 1234.6d 1226.2d 1217.8d 1209.5d Standard uncertainties are u(x1) = 0.0001; u(T) = ±0.01 K; u(ρ) = ±0.15 kg·m-3; u(p) = ±1kPa a This work. b Ref. 28. c Ref. 12. d Ref. 20.

348.15 978.8 1112.2 1187.2 1235.3 1268.7 1293.3a

1085.2 1136.2 1165.8 1185.6 1201.2d

The experimental densities of [HMPYR][NTf2], [DoMIM][NTf2] and PEA have been correlated as a function of pressure by the Tait equation.29 The original equation of Tait was published about 100 years ago to present the results of the density of fresh water and seawater as a function of pressures. During years, this equation was modified for different liquids to present density data over in a wide pressure ranges. These modifications are widely discussed in literature.29

, =

,

ln

!" !"

(2)

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where the reference pressure p0 = 0.1 MPa. Two parameters, ρ0 and B are assumed to be dependent on temperature according to the following equations:

# , # = ## + # /K + # /K

(3)

% = %# + % /K

(4)

The obtained parameters of the Eqs. 3 and 4 and the standard deviations presented in Eqn. 5 are listed in Table 2. The standard deviation σ is calculated according to the equation:

& = (∑.+/*+

exp

/

− +calc - /01

(5)

where n are the experimental points. Table 2. Parameters of the Correlation Equation (4) and the Standard Deviation, σ

[HMPYR][NTf2]

A· 102 6.8397

B/(MPa) B0/(MPa) = 251.62 B1/(MPa·K-1) = -0.43359

[DDMIM][NTf2]

7.6867

B0/(MPa) = 273.25 B1/(MPa·K-1) = -0.48556

PEA

8.1637

B0/(MPa) = 372.59 B1/(MPa·K-1) = -0.71219

ρ0/(kg·m-3) ρ00/(kg·m-3) = 1642.6 ρ01/(kg·m-3·K-1) = -1.1836 ρ02/(kg·m-3·K-2) = 5.1786 · 10-4 ρ00/(kg·m-3) = 1519.65 ρ01/(kg·m-3·K-1) = -0.9995 ρ02/(kg·m-3·K-2) = 2.3214 · 10-4 ρ00/(kg·m-3) = 1170.2 ρ01/(kg·m-3·K-1) = -0.28728 ρ02/(kg·m-3·K-2) = -7.5000 · 10-4

σ/(kg·m-3) 0.108

0.088

0.115

The result of correlation in the whole temperature range together with experimental data are presented for [HMPYR][NTf2], [DoMIM][NTf2] and PEA in Figs. 2-4, respectively. The pressure dependence of density becomes slightly nonlinear, especially at low

12


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temperatures. The correlation is presented with the average standard deviation σ = 0.104 kg·m-3.

Figure 2. Density, ρ, for the [HMPYR][NTf2] as a function of pressure, along isotherms. Experimental data: (●) T = 298.15K; (○) T = 308.15K; (■) T = 318.15K; (□) T = 328.15K; (♦) T = 338.15K; (◊) T = 348.15K. Solid lines represent Tait equation.

13



Figure 3. Density, ρ, for the [DoMIM][NTf2] as a function of pressure, along isotherms. Experimental data: (●) T = 298.15K; (○) T = 308.15K; (■) T = 318.15K; (□) T = 328.15K; (♦) T = 338.15K; (◊) T = 348.15K. Solid lines represent Tait equation.

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Figure 4. Density, ρ, for the PEA as a function of pressure, along isotherms. Experimental data: (●) T = 298.15K; (○) T = 308.15K; (■) T = 318.15K; (□) T = 328.15K; (♦) T = 338.15K; (◊) T = 348.15K. Solid lines represent Tait equation.

Isobaric expansivity (coefficient of thermal expansion), (α) of pure substances may be calculated from the density-temperature and pressure dependence from the equation given below:

340ρ5 3 6

α = − 2

(6)

The isothermal compressibility, (κ) presents the influence of pressure on density at constant temperature and is defined as:

15



340ρ 53 6

κ = − 2

(7)

The influence of temperature and pressure up to 40 MPa on the expansivities and isothermal compressibilities are presented in Figs. 5 and 6 for [DoMIM][NTf2] as an example and in Figs. S2-S5 in the SI for [HMPYR][NTf2] and PEA. They were calculated by means of the Tait equation. Both parameters are weak temperature and pressure dependent, which is typical for ILs. 298

308

318

328

338

348

7.2

7.2 p = 0.1MPa

7.0

7.0

1

2

104 ·α / K-1

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6.8

5

6.8

6.6

10

6.6

15

6.4

20 25

6.2

6.4 6.2

30 35

6.0

6.0

40

5.8

5.8

298

308

318

T /K

328

338

348

Figure 5. The isobaric expansivity, α of [DoMIM][NTf2] as a function of temperature T at constant pressure p. Solid lines are calculated from Eqs. (2) to (7) with the values of parameters shown in Table 2. The letter on the solid line corresponds to p/MPa.

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298

308

318

328

338

0.75

348 0.8 p = 0.1 MPa 1

2

0.70

κ / GPa-1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


5 10

0.65

0.7

0.7

15 20

0.60

0.6 25 30

0.55

35 40

0.6

0.50

0.5

0.45

0.5

298

308

318

T /K

328

338

348

Figure 6. The isothermal compressibility, κ of [DoMIM][NTf2] as a function of temperature T at constant pressure p. Solid lines are calculated by equations (2) to (7) with the values of parameters shown in Table 2. The letter on the solid line corresponds to p/MPa.

The values of α for two IL and PEA, calculated for different temperatures and pressures are presented in Table S5 in SI. Isobaric expansivities, α of ILs and PEA are in the range of 6.5 (0.1MPa) – 5.9 (40MPa) x 10−4 K−1 for [HMPYR][NTf2], 6.9 (0.1 MPa) – 6.2 (40MPa) ×10−4 K−1for [DoMIM][NTf2] and 7.2 (0.1MPa) – 6.5 (40MPa) × 10−4 K−1 for PEA at T = 298.15 K. The calculated values of isobaric expansivity of ILs and PEA are in a range of literature data for ILs, which are usually from 4 to 7 × 10−4 K−1.30-32 The values, observed for molecular organic liquids are larger and are in the range of10.7–14.3×10−4 K−1.33,34 The

17



Page 18 of 36

isobaric expansivity at different temperatures and pressures is also smaller than that for molecular organic liquids. For our ILs a small decrease in isobaric expansivity with an increasing temperature was observed and opposite trend for PEA was noted. Isothermal compressibility, κ of pure ILs and PEA slightly increases with increasing temperature for all three substances. The changes are in the range of 0.56 (0.1MPa) – 0.43 (40MPa) GPa−1 for [HMPYR][NTf2], 0.60 (0.1 MPa) – 0.47 (40MPa) GPa−1for [DoMIM][NTf2] and 0.51 (0.1MPa) – 0.42 (40MPa) GPa−1 for PEA at T = 298.15 K and at a measured range of pressures (see Table S6 in the SI). Both parameters decrease for all substances with an increasing pressure. In general, ILs with longer alkyl chain length substituent in the cation/anion are more compressible.

Comparing [HMPYR][NTf2], and [DoMIM][NTf2] we can see that

[DoMIM][NTf2] with dodecyl substituent is more compressible than [HMPYR][NTf2]. The value of κ for [DoMIM][NTf2] is 0.60 GPa−1 at T = 298.15 K, p = 0.1 MPa in comparison to 0.56 GPa−1 at T = 298.15 K, p = 0.1 MPa for [HMPYR][NTf2].

Excess Molar Volumes. The measurements of the density as a function of temperature and pressure in binary systems provide the possibility of the calculation of the excess molar volume, V E in the measured temperature range (298.15 - 348.15) K and pressure (0.1 - 40) MPa. Experimental V E data of (IL + PEA) are presented in Table S7 in the SI. The results are correlated by the well-known Redlich-Kister equation:

7 8 /9 9 = ∑.+/# :+ , 9 − 9 +

(8)

where x1 is the mole fraction of the IL and V E / (cm 3⋅ mol-1) is the excess molar volume. The model parameters ai are dependent on temperature and pressure in a linear form: 18


Page 19 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


:+ , /cm3 ·mol-1 = :+# + :+ ; /MPa − # < + :+ ;/K − #
F + ?9

IIexp

− 9IIcalc >F + ;9G

IIexp

− 9GIIcalc ><

(13) where P is the set of parameters vector, n is the number of experimental points, 9Iexp, 9GIexp and 9Icalc >, 9GIcalc >

are the experimental and calculated mole fractions of one phase and 9IIexp,

27



9G

IIexp

Page 28 of 36

and 9IIcalc >, 9GIIcalc > are the experimental and calculated mole fractions of the second

phase. Three binary parameters for pairs of three components, IL, PEA and water were regressed by minimizing the square of the differences between the experimental and calculated mole fractions of each component in two liquid phases. Calculations were made for binaries and ternaries data together. The calculated binary parameters and corresponding root-mean-square deviations (RMSD) are presented in Table 5. The RMSD values were calculated from the equation:

/

PQLP RMSD = K∑+ ∑L ∑M?9+LM − 9+LM F /6S T NO

(14)

where x is the mole fraction and the subscripts i, l, and m designate the component, phase, and tie-line, respectively. The results of the correlation are shown in Fig. 10 together with the experimental tie-lines. The NRTL equation presents satisfactory results. Table 5. Parameters and Root Mean Square Deviation of the NRTL Equationa for the Ternary System {[DoMIM][NTf2] (1) + PEA (2) + water (3)} ij gij/(J·mol-1) 12 -6745.78 13 4433.20 23 2949.25 a Parameter α = 0.4.

gji/(J·mol-1) 9634.32 12668.95 10737.61

RMSD σx 0.007

■ Conclusions The

densities

in

two

binary

systems

{1-hexyl-1-methylpyrrolidyne

bis{(trifluoromethyl)sulfonyl}imide, [HMPYR][NTf2], or 1-dodecyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide, [DoMIM][NTf2] + 2-phenylethanol (PEA)} in a wide range of temperature (298.15-348.15) K and pressure (0.1-40) MPa were measured. The Tait

28


Page 29 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


equations were used for the correlations of the experimental values of the densities as a function of pressure with the temperature-dependent parameters. Excess molar volumes, isobaric expansivities and isothermal compressibilities have been calculated as a function of temperature and pressure. This work is also aimed at investigating the influence of pressure on density and solubility. Solid-liquid phase equilibrium data for the binary mixture of {[DoMIM][NTf2] + PEA} has been measured at normal and high-pressure. The influence of high pressure is not significant. Additionally, the tie-lines in ternary system {[DoMIM][NTf2] + PEA + water} were experimentally determined using GC at temperature T = 308.15 K at p = 0.1 MPa. The solvent capacity, described by two parameters, the selectivity and the solute distribution ratio coefficients were calculated and compared to the literature data used in similar separation problem. The effect of the structure of the IL, the alkyl chain length in the cation and type of anion on the density, selectivity and solute distribution ratio were discussed. The obtained data at higher pressure and in LLE ternary systems with [DoMIM][NTf2] may suggest that the increasing pressure is not worth to be proposed for the technological use in PEA extraction. New IL, tested for this process, the [DoMIM][NTf2] shows average solute distribution ratio and selectivity. The present work needs the continuation of biosynthesis with Saccharomyces cerevisiae to grow and produce PEA in a presence of proposed entrainers.

Appendix A. Supplementary data Supplementary material related to this article can be found, in the online version, at http://dx.doi.org/Properties and purities of ILs and solvents, operation conditions in GC, densities measures with different methods, experimental densities of the binary systems {IL (1) + PEA (2)} as a function of temperature and pressure, plots of isobaric expansivity and isothermal compressibility, values of thermal expansion coefficients as a function of 29



Page 30 of 36

temperature and pressure, values of isothermal compressibility coefficient, values of the excess molar volumes as a function of temperature and pressure, coefficients of the Redlich – Kister equation, figures of VE, SLE data and figures for the {[DoMIM][NTf2] (1) + PEA (2)} binary system are presented. ■AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]. Phone: (+48) 22-6213115. Fax: (+48) 22-6282741. Notes The authors declare no competing financial interest. ■ ACKNOWLEDGEMENTS This work has been supported by the project of National Science Centre(NCN) in Poland under the project No. 2014/15/B/ST5/00136 for years 2015-2018.

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High-pressure

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Page 36 of 36

Ionic Liquids 2–Phenylethanol Water

SLE

LLE

Density

Isobaric expansivity

a

Excess molar volume VE

Isothermal compressibility


k

Phase Equilibrium Investigation on 2-Phenylethanol in Binary and

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