Measurements of Infinite Dilution Activity Coefficients of Alkanols in the

Article pubs.acs.org/jced

Measurements of Infinite Dilution Activity Coefficients of Alkanols in the Ionic Liquid Tributylmethylammonium Methyl Sulfate Using HSSPME/GC/FID Andrew Milli Elias and Gerson Luiz Vieira Coelho* Laboratory of Separation Processes, Department of Chemical Engineering, Federal Rural University of Rio de Janeiro, Seropédica-Rio de Janeiro City 23890-000, Brazil ABSTRACT: The activity coefficients at infinite dilution (γ∞ i ) and gas−liquid partition coefficients (KLG) for six solutes (methanol, ethanol, 1-propanol, 1-butanol, 2-butanol, and 2methyl-2-propanol) in the liquid ionic (IL) tributylmethylammonium methyl sulfate ([TBMA][CH3SO4]) were determined by HS-SPME (headspace-solid phase micro extraction) at four temperatures from 338.15 to 368.15 K. The values of partial molar excess enthalpies at infinite E,∞ E,∞ dilution (ΔHE,∞ i ), Gibbs free energies (ΔGi ), and entropies (ΔSi ) were also calculated from the γ∞ values. The results are unprecedented in the literature and suggest that SPME can be used i to determine activity coefficients at infinite dilution of solutes in liquid ionic solvents.

determined for all studied compounds using the value of γ∞ i obtained. The results are unprecedented in the literature.

1. INTRODUCTION Ionic liquids (ILs) are used as mass separating agents and, because of their potential use on an industrial scale, research in this area is one of the fastest growing fields in recent years.1 Information about solute−solvent interactions is of extreme importance to the separation process. Both the activity coefficient at infinite dilution and liquid−gas partition coefficient provide information about the quantitative and qualitative energy of intermolecular interactions,2 whereas γ∞ i allows for the selection of the best solvent for use in a separation process as well as the determination of parameters in thermodynamic models used in vapor−liquid equilibrium modeling.3,4 The main techniques used for the determination of the activity coefficient at infinite dilution with ionic fluids are gas− liquid chromatography (GLC) and gas stripping method (dilutor technique).5 The Headspace-Solid Phase Micro 6 Extraction is a novel methodology used to determine γ∞ i . Researchers have shown that SPME can be successfully used for the determination of partition coefficients7,8 and activity coefficients.3,4,6 The technique has advantages such as excellent reproducibility, easy implementation, and low cost, making it an excellent methodology for the determination of vapor−liquid equilibrium data.3 The main purpose of this study was to determine the activity coefficients in infinite dilution γ∞ i of six alcohols (methanol, ethanol, 1-propanol, 1-butanol, 2-butanol, and 2-methyl-2propanol) in ionic liquid ([TBMA][CH3SO4]). Values were determined by SPME at10 K intervals, and temperatures from 338.15 to 368.15 K. The gas−liquid partition coefficients (KLG) were determined as a function of temperature. Partial molar excess enthalpies at infinite dilution (ΔHE,∞ i ), Gibbs free energies (ΔGiE,∞), and excess entropies (ΔSiE,∞) were © XXXX American Chemical Society

2. EXPERIMENTAL METHOD 2.1. Material. Solutes (methanol, ethanol, 1-propanol, 1butanol, 2-butanol, 2-methyl-2-propanol, and o-xylene) were purchased from Sigma-Aldrich. All solutes were analyzed for purity by gas chromatography and refractometry; all showed purity higher than 0.9922 mass fractions. Alcohols were used without any additional purification process. SPME fibers with 100 μm PDMS coating and holders were purchased from Supelco. Data for compounds is available in Table 1. The solvent used was tributylmethylammonium methyl sulfate ([TBMA][CH3SO4]) (mass fraction ≥ 0.9500, M = 311.48 g·mol−1) supplied by BASF and purified by vacuum evaporation for 5 days at 80 °C. Purity was checked in two ways: (a) presence of traces of solvents through headspace analysis by SPME with PDMS coating, showing no impurities and (b) evaluation of the water mass fraction by the Karl Fisher analysis, which was less than 8.10−3. Figure 1 shows the structure of [TBMA][CH3SO4]:9 2.2. Gas Chromatography Conditions for SPME and Liquid Injections. The chromatograph used was a GC-2010 Shimadzu equipped with a 0.75 mm ID liner (SGE Analytical Science Pty) coupled to a HP-INNO wax column (60 m × 0.32 mm x 0.25 μm), coupled to a FID (Flame Ionization Detector). The injector and detector were maintained at 250 °C. Helium was used as the carrier gas (mass fraction 0.99999) in a column flow of 2.0 mL/min. The column was maintained at 50 °C for 5 Received: October 29, 2015 Accepted: April 14, 2016

A

DOI: 10.1021/acs.jced.5b00919 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

where Kfg is the fiber−gas partition coefficient, Vf is the volume of the polymeric coating of the SPME fiber, nfi is the mass of solute i on the fiber, ngi is the mass of solute in the gas phase, and Vg is the volume of gas phase. 2.5. Determination of Infinity Dilution Activity Coefficients by SPME. The solutions were prepared by adding 1.0 μL of alcohol to 3 mL of ionic liquid in a 40 mL amber vial capped with a PTFE/silicone septum. A stainless steel base was built to house the vial and resistances; caps were checked to ensure that no condensation was present. The temperature was controlled by a PID controller with PT-100 thermocouple (precision of 0.1 K) and a solid state relay. The system was magnetically stirred at rotations above 1500 rpm. Figure 2 shows a diagram depicting the experimental unit used.

Table 1. Compounds Used in This Study chemical name

source

methanol ethanol 1-propanol 1-butanol 2-butanol 2-methyl-2propanol o-xylene [TBMA] [CH3SO4]c

SigmaAldrich SigmaAldrich SigmaAldrich SigmaAldrich SigmaAldrich SigmaAldrich SigmaAldrich BASF

initial mass fraction purity

purification method

0.9968

none

0.9959

none

0.9980

none

0.9977

none

0.9961

none

0.9974

none

0.9922

none

0.9500

vacuum evaporation

final mass fraction purity

0.9920d

analysis method GCa and Rb GCa and Rb GCa and Rb GCa and Rb GCa and Rb GCa and Rb GCa and Rb SPMEe and KFf

a

Gas chromatography. bRefractometry. cTributylmethylammonium methyl sulfate. dWater mass fraction was less than 8.10−3. eSolid phase micro extraction. fKarl Fisher.

Figure 1. Structure of [TBMA][CH3SO4]9 Figure 2. Diagram of the experimental unit used.

min, ramped up to 90 °C at a rate of 10 °C/min, and maintained at this temperature for 2 min. 2.3. Construction of Calibration Curves. Standards solutions of solutes were prepared by successive dilutions of each studied alcohol in o-xylene. The concentrations used in the construction of calibration curves ranged from 8.90 to 2514.41 ng/μL; eight points were used, which were obtained by the injection of 1.4 μL standard solutions. Four to eight replicates were analyzed. The chromatographic conditions were the same as described above. 2.4. Determination of Extraction Time and Fiber−Gas Partition Coefficients. The determination of fiber−gas partition coefficients was made using gaseous samples prepared by spiking 1.0 μL of o-xylene stock solution into 44 mL amber vials, capped with a PTFE/silicone septum. Extraction time was determined by studying KLG over time. PDMS fibers were exposed to the vial after 10 min of gas sample injection. The extraction interval ranged from 1 to 60 min. The mass extracted by each fiber was measured by gas chromatography using the conditions described above. Temperatures were maintained at 338.15 K in a thermostatic bath with a precision of 0.1 K. Gas-fiber partition coefficients were subsequently determined at all studied temperatures (338.15 to 368.15 K) using the predetermined extraction time. The calculation of the fiber−gas partition coefficient Kfg is presented in equation4 K fg =

nif Vg Vf nig

The equilibration time was measured by headspace extraction with 100 μm PDMS fiber after 20, 30, 40, and 90 min of agitation. After agitation, the system was maintained at constant temperature for 30 min. The fiber was exposed on the gas chromatograph’s injector for the quantification of the extracted material. After each desorption, the fiber was re-exposed to verify the presence of nondesorbed material. The activity coefficient at infinite dilution was determined using eq 2 described below. Molar volumes of solutes were calculated using the Rackett equation,10 and second virial coefficients by the Tsonopoulos correlation.11 Vapor pressure was determined by the Wagner equation.10 The complete and very detailed description of the thermodynamic principles followed the formulation of Furtado and Coelho.4 Equation 2 is a modification of the Everett12 and Cruickshank et al.13 equations ⎛ ρ RT ⎞ P sat(B11 − vi0) ln(γi∞) = ln⎜ s sat ⎟ − i RT ⎝ KLGPi Ms ⎠

(2)

γ∞ i

where is the activity coefficient at infinite dilution of solute i, ρs is the solvent density, R is the gas constant, T is the system temperature, KLG is the partition coefficient liquid−gas at infinite dilution, Psat i is the saturation pressure of the solute at temperature T, Ms is the molar mass of solvent, B11 is the second virial coefficient, and v0i is the molar volume of solute as liquid.

(1) B



Article

The KLG gas−liquid partition coefficient was determined by the first approach presented in Furtado and Coelho,4 which is shown in eq 3 KLG

⎡ ⎤ ⎛ n0 ⎞ 1 = ⎢K fgVf ⎜⎜ if − 1⎟⎟ − Vg ⎥ V ⎢⎣ ⎥ ⎝ ni ⎠ ⎦ L

Table 3. Summary of Values of Solute Properties at Different Temperaturesa B11/(m3/mol) methanol ethanol 1-propanol 1-butanol 2-butanol 2-methyl-2-propanol

(3)

where n0i is the initial mass of solute i in the system, and VL is the volume of liquid phase. 2.6. Statistical Tests. Three SPME fibers (100 μm PDMS) were tested for the verification of interfiber reproducibility. The test was carried out through the analysis of fiber−gas partition coefficients of solutes at 338.15 K. The results were compared using ANOVA tests. After the conclusion of experiments, each fiber was analyzed by the t tests to ensure that no loss of polymeric material occurred.

methanol ethanol 1-propanol 1-butanol 2-butanol 2-methyl-2-propanol

3. RESULTS AND DISCUSSION Determined calibration curves are used to correlate the chromatographic peak area for an injected mass. All built


Table 2. Fiber−Gas Partition Coefficient Kfg for All Compounds Studied at p = 0.1 MPa and Temperatures from 338.15 to 368.15 Ka Kfg ± SDb

solute i methanol ethanol 1-propanol 1-butanol 2-butanol 2-methyl-2-propanol methanol ethanol 1-propanol 1-butanol 2-butanol 2-methyl-2-propanol

T = 338.15 K 16.0 ± 0.7 25.4 ± 0.3 38.7 ± 0.9 103.3 ± 1.6 54.7 ± 1.5 43.0 ± 1.2 T = 358.15 K 6.1 ± 0.1 12.4 ± 0.2 18.8 ± 0.3 54.4 ± 0.6 28.7 ± 1.2 22.2 ± 0.8


T = 348.15 K 11.0 ± 0.8 19.0 ± 0.4 26.3 ± 0.4 71.1 ± 2.0 42.3 ± 0.2 30.1 ± 0.3 T = 368.15 K 4.1 ± 0.2 8.0 ± 0.1 12.3 ± 0.1 35.7 ± 0.5 21.3 ± 0.1 14.0 ± 0.1

T = 338.15 −0.0006 −0.0009 −0.0013 −0.0017 −0.0015 −0.0013 T = 348.15 −0.0006 −0.0008 −0.0012 −0.0016 −0.0014 −0.0012 T = 358.15 −0.0005 −0.0008 −0.0011 −0.0015 −0.0013 −0.0011 T = 368.15 −0.0005 −0.0007 −0.0010 −0.0013 −0.0012 −0.0010

v0i /(m3·108)

−2 Psat i /(Pa·10 )

4457 5609 6841 8397 8761 8765

1033 586 258 104 232 487

4538 5709 6951 8517 8890 8927

1509 8909 409 172 370 752

4619 5815 7067 8644 9047 9099

2155 1317 6277 274 570 1124

4709 5929 7190 8776 9203 9283

3012 1897 934 423 850 1627

K

K

K

K

a

All constants used in the calculations were taken from the literature.10,11

Table 4. Partition Coefficients at Infinite Dilution KLG for Six Alcohols i in Ionic Liquid [TBMA][CH3SO4] at p = 0.1 MPa and Different Temperatures, 338.15 to 368.15 Ka solute i

a

Standard uncertainty u(T) = 0.1 K, u(p) = 10 kPa, and relative standard uncertainty ur(Kfg) = 2%. bSD is standard deviation.

methanol ethanol 1-propanol 1-butanol 2-butanol 2-methyl-2-propanol methanol ethanol 1-propanol 1-butanol 2-butanol 2-methyl-2-propanol

KLG ± SDb T = 338.15 K 661.5 ± 12.6 728.2 ± 2.0 1312.9 ± 35.8 2273.6 ± 14.6 1253.8 ± 9.0 748.4 ± 17.7 T = 358.15 K 473.5 ± 15.8 486.5 ± 14.5 831.8 ± 4.6 1517.2 ± 12.0 920.0 ± 17.8 478.2 ± 13.3

T = 348.15 K 548.0 ± 32.8 604.8 ± 10.9 1026.7 ± 8.3 1827.8 ± 31.9 1090.0 ± 16.9 587.2 ± 19.6 T = 368.15 K 434.5 ± 39.1 430.0 ± 2.8 728.3 ± 3.0 1165.1 ± 12.1 809.0 ± 11.1 407.8 ± 9.9

a

Standard uncertainty u(T) = 0.1 K, u(p) = 10 kPa, and relative standard uncertainty ur(KLG) = 4%. bSD is standard deviation. Figure 3. Plot of ln Kfg vs 1/T for solutes and the linear correlation of the data.

erroneous determination does not ensure that the equilibrium between phases has fully occurred. Extractions used 100 μm PDMS fibers and extraction times ranged from 5 to 20 min. An extraction time of 30 min was used to ensure equilibrium between phases. The fibers were re-exposed to the chromato-

curves showed a correlation coefficient greater than 0.9991, which ensures great accuracy in the peak-mass ratio. Extraction time is one of the fundamental pieces in the correct determination of thermodynamic properties because an C



Article

phases. It is important in determining the liquid−gas partition coefficient and the subsequent determination of the activity coefficient. The Kfg was determined at the studied temperatures (Table 2). To ensure that the determination of the fiber gas partition coefficient maintained consistency, data linearization as a function of temperature was conducted. The linearization of the fiber gas partition coefficient facilitates the analysis of the dependency on temperature variation.14 In all studied alcohol− IL systems, a decrease of Kfg values with increasing temperatures was observed. Furthermore, all correlation coefficients were higher than 0.9870, which ensures the good precision and linearity in the experimentally obtained data. Figure 3 shows the plot of measured ln Kfg versus 1/T values, and the linear correlation of the data. The fiber−gas partition coefficients showed low values for molecules with high polarity, which is due to the nonpolar characteristics of PDMS. High polarity molecules show less interaction with PDMS polymer, which explains the low values observed for methanol. This is evident within the group of alcohols with four carbons because of the high values of Kfg for 1-butanol.15 The B11, v0i , and Psat i values were calculated for each studied alcohol by the determination of activity coefficients at infinite dilution (Table 3). The liquid ionic density was calculated using eq 4 as presented in the literature. The a, b, and c values of coefficients used were 1.23977 g·cm−3, − 6.203 × 104 g·cm−3, and 0.1457 × 107 g·cm−3, respectively. The value of the ionic liquid density ρs decreased with increasing temperatures16

Figure 4. Plot of ln KLG vs 1/T for solutes and the linear correlation of the data.

Table 5. Experimental Activity Coefficients at Infinite Dilution i for Various Solutes in Ionic Liquid Tributylmethylammonium Methyl Sulfate ([TBMA][CH3SO4]) p = 0.1 MPa, and at Different Temperatures, 338.15 to 368.15 Ka γ∞ i

solute i methanol ethanol 1-propanol 1-butanol 2-butanol 2-methyl-2-propanol metanol etanol 1-propanol 1-butanol 2-butanol 2-methyl-2-propanol

T = 338.15 K 0.16 0.24 0.29 0.40 0.38 0.32 T = 358.15 K 0.14 0.19 0.21 0.25 0.24 0.25

T = 348.15 K 0.15 0.20 0.24 0.31 0.29 0.28 T = 368.15 K 0.13 0.17 0.18 0.22 0.20 0.23

ρs = a + b(T ) + c(T )2

(4)

The equilibration time used in all infinite dilution experiments was 40 min. This was determined through the evaluation of equilibrium times for all alcohols. The longest equilibrium time was 25 min. Forty minutes was used to ensure equilibrium. The correct determination of extraction and equilibrium times ensures the precise determination of the thermodynamic properties of systems.14 The gas−liquid partition coefficients KLG were determined for all six alcohols in ionic liquid [TBMA][CH3SO4] at temperatures from 338.15 to 368.15 K (Table 4). As expected, KLG values decrease with increasing temperatures. This results from a dominant temperature dependency on the evaporation enthalpy, and is directly linked to the process of sorption in the PDMS fiber. Figure 4 shows the plot of measured ln KLG versus 1/T values, and the linear correlation of the data. All linear correlation coefficients were equal or more than 0.9815 for all compounds, which ensures good precision and linearity in the experimentally obtained data. The activity coefficients at infinite dilution γ∞ i values (Table 4) were determined using a gas−liquid partition coefficient (Table 5). A typical influence of temperature on the activity coefficient behavior can be observed. Increased temperature decreased the amount of γ∞ i for all studied alcohols. This behavior is due to the reduction of solvent−solute repulsive forces, especially noticeable in the compounds with low polarity.17 Low values of γ∞ i signify strong interactions between solute and solvent. The highest values of activity coefficients can be observed in alcohols with high carbon number. The polar IL

a

Standard uncertainty u(T) = 0.1 K, u(p) = 10 kPa, and relative standard uncertainty ur(γ∞ i ) = 4%.

Figure 5. Plot of ln γ∞ i vs 1/T for solutes and the linear correlation of the data.

graph’s injector after each extraction, and no nondesorbed material was detected. The fiber gas partition coefficient represents a property that relates the proportion of the analyte concentration in equilibrium at each phase involved, that is, gas and fiber D



Article

Table 6. Activity Coefficients at Infinite Dilution γ∞ i298.15K at 298.15 K Calculated through Equation 5; Values of the Partial Molar E,∞ E,∞ Excess Enthalpies at Infinite Dilution, ΔHi , Entropies, Tref·ΔSE,∞ i , and Gibbs Free Energies, ΔGi , of Alcohols i in a [TBMA][CH3SO4] at the Reference Temperature of Tref = 298.15 K and p = 0.1 MPa

a

solute i

γ∞ i298.15K

−1 ΔHE,∞ i /kJ·mol

−1 Tref·ΔSE,∞ i /kJ·mol

−1 ΔGE,∞ i /kJ·mol


0.23 0.40 0.62 1.06 1.06 0.55

7.15 11.28 16.20 20.85 21.93 11.45

10.84 13.54 17.38 20.71 21.78 12.94

−3.69 −2.26 −1.17 0.14 0.15 −1.49

E,∞ E,∞ −1 −1 −1 Standard uncertainties (u) are as follows: u(ΔHE,∞ i ) = 0.5 kJ mol , u(ΔGi ) = 0.5 kJ mol , and u(Tref·ΔSi ) = 0.5 kJ mol .

Table 7. Interfiber Comparison by the ANOVA Test with 95% Confidence Level Using the Fiber−Gas Partition Coefficient Determined at T = 338.15 K and p = 0.1 MPaa Kfg + SDb solute methanol ethanol 1-propanol 1-butanol 2-butanol 2-methyl-2-propanol

fiber 1 15.62 25.41 38.31 104.23 54.94 43.62

± ± ± ± ± ±

0.19 0.31 0.23 0.25 0.45 0.37

statistical tests results

fiber 2 15.39 25.92 38.97 103.77 54.13 43.14

± ± ± ± ± ±

fiber 3

0.22 0.63 0.69 0.42 0.20 0.43

15.71 25.03 38.14 104.30 54.13 43.54

± ± ± ± ± ±

0.39 0.50 0.27 0.50 0.21 0.41

F-value

result

1.048 2.453 2.884 1.518 4.791 1.207

pass pass pass pass pass pass

a Three replicates for each fiber; Fcrit = 5.143. Standard uncertainty u(T) = 0.1 K, u(p) = 10 kPa, and relative standard uncertainty ur(Kfg) = 2%. bSD, standard deviation.

analyzed for each solute. All analyzed fibers were statistically equivalent by the ANOVA tests at 95% of confidence level (Table 7). The fibers were used in all experiments. The t test was used to analyze possible polymeric material losses in the PDMS fibers, caused by conditions of high swelling rates.4 The partition coefficients of solutes were determined before and after the experiments, in three replicates for each fiber, and compared using the t test at 95% confidence level. All fibers passed in t test at 95% confidence level (Table 8).

used strongly interacts with the studied alcohols because of the presence of the − OH group.18 The lowest values were observed for 2-methyl-2-propanol, which contains the same number of carbons as the other studied alcohols, that is, four carbons, due to its high polarity. Figure 5 shows the plot of measured ln γ∞ i versus 1/T values and the linear correlation of the data; the infinite dilution activity coefficient dependency on temperature can be observed. The plots show the fitting quality of eq 5. The γ∞ i variation in 1-butanol and 2-butanol with increasing temperatures were stronger than in the other alcohols. The measured values for the four-carbon series were very similar at the highest tested temperature, indicating a significant decrease in repulsive forces between the carbon chain and IL. The dependency relationship between activity coefficients at infinite dilution and temperature can be demonstrated through the enthalpy and entropy terms in eq 519 ln(γi∞) =

HiE, ∞ S E, ∞ − i RT R

4. CONCLUSION The HS-SPME/GC/FID method was employed to measure the γ∞ i infinite dilution activity coefficients in a series of six alcohols in ionic liquid [TBMA][CH3SO4], and at four temperatures. The activity coefficients in infinite dilution determined in the studied systems showed two interesting features: increasing temperatures increases attraction between solute and solvent and results in decreased activity coefficients; reduction in chain lengths of alkanols in [TBMA][CH3SO4] results in reduced activity coefficients. The solid phase microextraction SPME was validated as an efficient, rapid, and inexpensive technique that ensures satisfactory values in the determination of activity coefficients at infinite dilution. The results are unprecedented in the literature and suggest that SPME can be used to determine activity coefficients at infinite dilution of solutes in liquid ionic solvents with the possibility of use on an industrial scale. Future detailed studies on the ionic term of the partition coefficient might contribute in supporting the proposed SPME use.

(5)

Using eq 5, the activity coefficient at infinite dilution was calculated at the reference temperature of 298.15 K to determine entropy and excess molar Gibbs free energy. The E,∞ E,∞ γ∞ values are presented in Table 5. i298.15K, Tref·ΔSi , and ΔHi The value of molar excess enthalpy for all compounds was positive. This is consistent with the dependency of the activity coefficient on temperature and decreases with increasing temperatures. The limiting partial molar excess Gibbs free energies GE,∞ = RTln γ∞ i i of all studied solutes in [TBMA][CH3SO4], at the reference temperature of 298.15 K, are presented in Table 6. The ANOVA statistical test was used to verify interfiber reproducibility. The analysis of PDMS fibers was performed by the determination of fiber−gas partition coefficients at 338.15 K. Three replicates for each of the three studied fibers were E



Article

Table 8. Interfiber Comparisons by the t Test with 95% Confidence Level Using Partition Coefficients Determined at T = 338.15 K and p = 0.1 MPa, before and after the Experimentsa statistical tests results

fiber 1 solute methanol ethanol 1-propanol 1-butanol 2-butanol 2-methyl-2propanol

before 15.62 25.41 38.31 104.23 54.61 43.62

± ± ± ± ± ±

after

0.19 0.31 0.23 0.25 0.25 0.37

15.41 25.54 38.62 104.54 54.65 43.20

± ± ± ± ± ±

0.40 0.49 0.32 0.55 0.49 0.33

methanol ethanol 1-propanol 1-butanol 2-butanol 2-methyl-2propanol

before 15.39 25.92 38.97 103.77 54.13 43.14

± ± ± ± ± ±

after

0.22 0.63 0.69 0.42 0.20 0.43

15.23 24.91 38.21 104.35 54.42 43.33

± ± ± ± ± ±

0.14 0.61 0.28 0.44 0.26 0.27

solute

before 15.71 25.03 38.14 104.30 54.13 43.54

± ± ± ± ± ±

0.39 0.50 0.27 0.50 0.21 0.41

result

0.834 −0.409 −1.355 −0.883 0.753 1.474


T-value

result

1.070 2.006 1.775 −1.636 −1.545 −0.635



fiber 3 methanol ethanol 1-propanol 1-butanol 2-butanol 2-methyl-2propanol

T-value


fiber 2 solute

Systems by Solid Phase Microextraction-GC-FID. Quim. Nova 2014, 37, 1177−1181. (4) Furtado, F. A.; Coelho, G. L. V. Determination of Infinite Dilution Activity Coefficients using HS-SPME/GC/FID for Hydrocarbons in Furfural at Temperatures of (298.15. 308.15. and 318.15) K. J. Chem. Thermodyn. 2012, 49, 119−127. (5) Dobryakov, Y. G.; Tuma, D.; Maurer, G. Activity Coefficients at Infinite Dilution of Alkanols in the Ionic Liquids 1-Butyl-3Methylimidazolium Hexafluorophosphate. 1-Butyl-3-Methylimidazolium Methyl Sulfate And 1-Hexyl-3-Methylimidazolium Bis(Trifluoromethylsulfonyl) Amide using the Dilutor Technique. J. Chem. Eng. Data 2008, 53, 2154−2162. (6) Fonseca, D. B.; Coelho, G. L. V. Determination of the Activity Coefficient at Infinite Dilution (γ∞) by Solid Phase Microextraction (SPME). Quim. Nova 2007, 30, 1606−1608. (7) Dohnal, V.; Vrbka, P.; Rehák, K.; Böhme, A.; Paschke, A. Activity Coefficients and Partial Molar Excess Enthalpies at Infinite Dilution for four Esters in Water. Fluid Phase Equilib. 2010, 295, 194−200. (8) Böhme, A.; Paschke, A.; Vrbka, P.; Dohnal, V.; Schuurmann, G. Determination of Temperature-Dependent Henry’s Law Constant of four Oxygenated Solutes in Water using Headspace Solid-Phase Microextraction Technique. J. Chem. Eng. Data 2008, 53, 2873−2877. (9) Ramdin, M.; Vlugt, T. J. H.; de Loos, T. W. Solubility of CO2 in the Ionic Liquids (TBMN) (MeSO4) and (TBMP) (MeSO4). J. Chem. Eng. Data 2012, 57, 2275−2280. (10) Reid, R. C.; Prausnitz, J. M.; Poling, B. E. The Properties of Gases and Liquids; McGraw Hill: New York, 1987. (11) Gmehling, G.; Kolbe, B. Thermodynamik; George Thieme Verlag: Stuttgart, Germany, 1988. (12) Everett, D. H. Effect of Gas Imperfection on G.L.C. Measurements: A Refined Method for Determining Activity Coefficients and Second Virial Coefficients. Trans. Faraday Soc. 1965, 61, 1637−1645. (13) Cruickshank, A. J. B.; Gainey, B. W.; Hicks, C. P.; Letcher, T. M.; Moody, R. W.; Young, C. L. Gas − Liquid Chromatographic Determination of Cross − Term Second Virial Coefficients using Glycerol. Benzene + Nitrogen and Benzene + Carbon Dioxide at 50°C. Trans. Faraday Soc. 1969, 65, 1014−1031. (14) Pawliszyn, J. Solid Phase Microextraction, Theory and Practice; Wiley-VCH: New York, 1997. (15) Martos, P. A.; Pawliszyn, J. Calibration of Solid Phase Microextraction for Air Analyses Based on Physical Chemical Properties of the Coating. Anal. Chem. 1997, 69, 206−215. (16) Jacquemin, J.; Goodrich, P.; Jiang, W.; Rooney, D. W.; Hardacre, C. Are Alkyl Sulfate-Based Protic and Aprotic Ionic Liquids Stable with Water and Alcohols? A Thermodynamic Approach. J. Phys. Chem. B 2013, 117, 1938−1949. (17) Domanska, U.; Marciniak, A. Activity Coefficients at Infinite Dilution Measurements for Organic Solutes and Water in the Ionic Liquid 1-Butyl-3-Methylimidazolium Trifluoromethanesulfonate. J. Phys. Chem. B 2008, 112, 11100−11105. (18) Domanska, U.; Królikowska, M. Measurements of Activity Coefficients at Infinite Dilution in Solvent Mixtures with ThiocyanateBased Ionic Liquids using GLC Technique. J. Phys. Chem. B 2010, 114, 8460−8466. (19) Ge, M.-L.; Lu, C.-Y.; Liu, X.-Y.; Li, X.-B.; Chen, J.-Y.; Xiong, J.M. Activity Coefficients at Infinite Dilution of Alkanes, Alkenes, Alkyl Benzenes in Dimethylphosphate based Ionic Liquids Using Gas− Liquid Chromatography. J. Chem. Thermodyn. 2015, 91, 279−285.

after 15.89 25.80 38.52 104.59 54.45 43.72

± ± ± ± ± ±

0.16 0.14 0.51 0.38 0.40 0.25

T-value

result

−0.721 2.131 −1.142 −0.797 −1.219 −0.630


a Kfg ± standard deviation; three replicates for each fiber; tcrit = 2.132. Standard uncertainty u(T) = 0.1 K, u(p) = 10 kPa, and relative standard uncertainty ur(Kfg) = 2%.

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel.: +55(21) 3787 3742. Fax: +55 (21) 3787 3750. Address: Departamento de Engenharia ́ Quimica, Universidade Federal Rural do Rio de Janeiro, BR 465, KM 7, Seropédica, Rio de Janeiro, Brasil. CEP: 23.851970. Funding

The authors are thankful for the financial support from FAPERJ, Rio de Janeiro, Brazil. Notes

The authors declare no competing financial interest.

■

REFERENCES

(1) Domanska, U.; Lukoshko, E. V.; Wlazło, M. Measurements of Activity Coefficients at Infinite Dilution for Organic Solutes and Water in the Ionic Liquid 1-Hexyl-3-Methylimidazolium Tetracyanoborate. J. Chem. Thermodyn. 2012, 47, 389−396. (2) Ge, M.-L.; Deng, X.-M.; Zhang, L.-H.; Chen, J.-Y.; Xiong, J.-M.; Li, W.-H. Activity Coefficients at Infinite Dilution of Organic Solutes in the Ionic Liquid 1-Butyl-3-Methylimidazolium Methyl Sulfate. J. Chem. Thermodyn. 2014, 77, 7−13. (3) Elias, A. M.; Furtado, F. A.; Coelho, G. L. V. Determination of the Activity Coefficient at Infinite Dilution in Ethanol-Water-Salt F


Measurements of Infinite Dilution Activity Coefficients of Alkanols in the

Recommend Documents