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Article Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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Determination of Activity Coefficients at Infinite Dilution of Solutes in N,N′‑Di(2-ethylhexyl)isobutyramide Using Inverse Gas−Liquid Chromatography K. Panneerselvam,* R. Karunakaran, and Ashish Jain

J. Chem. Eng. Data Downloaded from pubs.acs.org by CALIFORNIA STATE UNIV FRESNO on 11/30/18. For personal use only.

Materials Chemistry & Metal Fuel Cycle Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu 603 102, India S Supporting Information *

ABSTRACT: Activity coefficients at infinite dilution for 30 solutes (alkanes, alkenes, alkyl benzenes, ketones, chloromethanes, aromatic compounds, acetonitrile, formaldehyde, and ethyl acetate) in N,N′-di(2-ethylhexyl)isobutyramide have been determined at temperatures T = (323.15 to 373.15) K by inverse gas chromatographic technique. Net retention volumes of solutes have been measured as a function of temperature. From the temperature dependence of the activity coefficients at infinite dilution, partial molar excess enthalpies and activity coefficients at infinite dilution at 298.15 K of solutes in N,N′-di(2-ethylhexyl)isobutyramide have been derived. Selectivity values at infinite dilution have been computed from the activity coefficients at infinite dilution values.

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INTRODUCTION The plutonium uranium redox extraction (PUREX) process uses tri-n-butyl phosphate (TBP) diluted with n-dodecane as solvent to recover uranium and plutonium from the solution of irradiated nuclear fuel. TBP is potentially vulnerable to third phase formation, and its degradation products can complicate recovery of extracted metal ions from the organic phase. It has adverse effects such as the inability to incinerate used solvent leading to large volumes of secondary low level radioactive waste. N,N′-Dialkyl monoamides have been considered as potential alternate solvent for the PUREX process to overcome this limitation which would potentially decrease the volume of low level waste associated with nuclear fuel recycle. N,N′Dialkyl monoamides have been developed for the PUREX process to selectively recover uranium(VI) and plutonium(IV) from fission products from the solution of irradiated nuclear fuel. The branched-chain N,N′-dialkyl monoamides have been developed for thorium uranium extraction (THOREX) processes which selectively recover uranium and thorium from the solution of irradiated nuclear fuel.1−5 The choice of solvent for extraction is determined by a combination of physical properties and solvation characteristics. Solvation behavior is generally characterized by polarity, solvent selectivity, capability of the solvent to interact with other compounds by intermolecular interactions, and its solubility. Spectroscopic and chromatographic methods are used to establish solvent strength and solvent selectivity, respectively. Inverse gas−liquid chromatography has become a widely accepted technique for measuring several thermodynamic properties, namely, activity coefficient at infinite dilution, Flory−Huggins interaction parameter, solubility parameter, © XXXX American Chemical Society

partition coefficient, and diffusion coefficients of various solutes in solvents.6−12 Activity coefficients at infinite dilution (γ∞ 13) of solute in solvent provide basic information on the intermolecular interactions between solute and solvent at infinite dilution.13−17 It is used for characterizing the behavior of liquid mixtures for estimation of mutual solubility, screening solvents for extraction, extractive distillation processes, and calculation of limiting separation factors. It can also be used to calculate basic thermodynamics functions, such as partial molar excess Gibbs energies, molar sorption enthalpies, and entropies over the relevant temperature range. This paper describes the determination of γ∞ 13 (where 1 and 3 refer to solute and solvent, respectively) of volatile solutes in N,N′-di(2-ethylhexyl)isobutyramide (solvent).

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EXPERIMENTAL SECTION Materials. The synthesis and characterization of N,N′-di(2ethylhexyl)isobutyramide (D2EHIBA) was carried out as described elsewhere.18,19 1H NMR and 13C NMR spectra are provided for synthesis of D2EHIBA in the Supportin Information as Tables S1 and S2 and Figures S1 and S2. Its mass fraction purity was above 98.5%. The gas−liquid chromatographic method was used to determine the purity of D2EHIBA. A 1 m long stainless steel (304 grade) tube having outer diameter of 3.2 mm was used for column packing. Chromosorb WAW (80/100 mesh) was used as solid support material. The solutes were injected into the mobile phase by Received: July 21, 2018 Accepted: November 9, 2018

A

DOI: 10.1021/acs.jced.8b00635 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

Table 1. Origin and Analysis of the Solutesa and N,N′-Di(2ethylhexyl)isobutyramide

using microliter syringes having 1 μL capacity. The linear and branched hydrocarbons with alkyl chain length from C5 to C11 (n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, 2,2,4-trimethylpentane, 2-methylpentane, 1-hexene, 1-heptene, 1-octene, and 1-decene), cyclohexane, benzene, toluene, p-xylene, m-xylene, ethylbenzene, propylbenzene, butylbenzene, dichloromethane, trichloromethane, tetrachloromethane, acetone, 3-hexanone, 2-heptanone, acetonitrile, formaldehyde, and ethyl acetate were used as procured. Their mass fraction purities were above 99% according to specifications, and the stated purity was confirmed by gas− liquid chromatography. A Shimadzu GC−9A gas chromatograph, 2 m × 3.2 mm of 10% SE-30 packed column fitted in the gas chromatograph, was used for determining degree of purity of D2EHIBA and solutes. Argon was used as the mobile phase with a flow rate 45 mL/min. Hydrogen and air were fed into the flame ionization detector with flow rates of 50 mL/ min and 500 mL/min, respectively, for aiding the combustion of the separated compounds. The origin and purity of solutes and N,N′-di(2-ethylhexyl)isobutyramide are given in Table 1. Apparatus and Experimental Procedure. The methods of column preparation and solvent packing used in this work have been described elsewhere.16,17,20−23 The stationary phase was prepared by dissolving, weighed amounts of purified D2EHIBA and Chromosorb WAW in dichloromethane. Dichloromethane was used as slurry solvent to coat D2EHIBA onto Chromosorb WAW. Dichloromethane was then completely evaporated from the solution using a rotary evaporator and was confirmed by gravimetric analysis. The masses were exactly weighed by an electronic balance with an accuracy of 0.0001 g. The mass fraction of D2EHIBA coating was 10.28% of Chromosorb WAW. The phase loading was obtained gravimetrically. The number of moles of D2EHIBA in the column was determined. One end of the column was attached to a pump to create suction down the length of the column, while a funnel was attached to the other end. The prepared stationary phase was poured through the funnel slowly. A small spatula was used for tapping the column along its length to ensure that the mixture was tightly packed throughout the entire column. The column was tapped until the level of the mixture in the funnel remained constant. After packing the column, the glass wool was inserted at both ends of the column to prevent the packing from being blown out by mobile phase flowing through the column. Prior to experiment, the prepared column was conditioned by passing the dry mobile phase through the column for about 10 h. A temperature higher than the experimental temperature was maintained to remove traces of volatile materials left in the packing and to presaturate the packing with mobile phase. The experiments were carried out using a gas−liquid chromatography (Shimadzu GC−9A) equipped with a thermal conductivity detector (TCD). The temperature of injection port and TCD were maintained at 423.15 K. A solute volume of 0.2 μL was injected and considered to be at infinite dilution on the column. An amount of 100 μL of air was injected as nonretainable compound. The retention time (t0) of air was utilized to compute adjusted retention time (tR′) of solutes. Measurements were carried out at T = (323.15 to 373.15) K. The column temperature was maintained within 0.1 K using a programmable controller present in the gas chromatograph. The retention time of solutes and air was measured in triplicate to ensure reproducibility, and it was found to be within (0.001−0.01) min. The inlet pressure (Pi) was measured by a

solutes

CAS registry number

n-pentane n-hexane n-heptane n-octane n-nonane n-decane n-undecane cyclohexane 1-hexene

109-66-0 110-54-3 142-82-5 111-65-9 111-84-2 124-18-5 1120-21-4 110-82-7 592-41-6

1-heptene 1-octene

592-76-7 111-66-0

1-decene benzene toluene ethylbenzene n-propylbenzene n-butylbenzene p-xylene m-xylene dichloromethane trichloromethane tetrachloromethane

872-05-9 71-43-2 108-88-3 100-41-4 103-65-1 104-51-8 106-42-3 108-38-3 75-09-2 67-66-3 56-23-5

acetone

67-64-1

3-hexanone 2-heptanone acetonitrile formaldehyde ethyl acetate

589-38-8 110-43-0 75-05-8 50-00-0 141-78-6

2,2,4-trimethylpentane 2-methylpentane D2EHIBAc

540-84-1 107-83-5 ---

supplier Alfa Aesar Alfa Aesar Alfa Aesar TCI Alfa Aesar Alfa Aesar Alfa Aesar Alfa Aesar SigmaAldrich Alfa Aesar SigmaAldrich TCI Alfa Aesar Alfa Aesar TCI TCI TCI Alfa Aesar Alfa Aesar Alfa Aesar Alfa Aesar SigmaAldrich SigmaAldrich TCI TCI Alfa Aesar Alfa Aesar SigmaAldrich TCI TCI Synthesis

mass fraction purity 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 ACSb 0.99 0.99 0.99 0.99

a

GC methods. bACS grade. cN,N′-Di(2-ethylhexyl)isobutyramide. Its CAS registry number is to be assigned. The purity of the degassed N,N-di(2-ethylhexyl)isobutyramide was determined by gas−liquid chromatography. Its mass fraction purity was found to be greater than 0. 99.

pressure gauge installed on the gas chromatograph. The outlet pressure (P0) was equal to the atmospheric pressure. The pressure drop (Pi − P0) varied depending on the flow rate of the mobile phase. The helium flow rate was measured using a calibrated soap bubble digital flow meter which was placed at the outlet after the detector. The results were corrected for water vapor. The software was used for data acquisition, analysis, and creating reports of chromatograms, etc. Theoretical Basis. The retention time of a solute depends on its partition between the stationary and mobile phase. It is an indication of interaction strength between the solute and liquid phase. It can be converted into net retention volume, which is directly related to the various physicochemical properties of the compounds. The net retention volume, VN, was calculated with the following equation:24 VN = J23U0(t R − t0) B

(1) DOI: 10.1021/acs.jced.8b00635 J. Chem. Eng. Data XXXX, XXX, XXX−XXX


Article

The adjusted retention time (tR − t0) was taken as a difference between the retention time of a solute and that of the air, and U0 is the flow rate after applying correction. The factor “J32” corrects for the influence of pressure drop along the column and is given by25 3 2 [(pi /p0 ) − 1] 3 [(pi /p0 )2 − 1]

J23 =

Table 2. Critical Constants and Ionization Potential of Solutes and Mobile phase

(2)

where Pi and P0 are inlet and outlet pressures. The activity coefficient at infinite dilution (γ∞ 13) for a solute, partitioned between helium and nonvolatile solvent (D2EHIBA), was computed from the net retention volume (VN) of solute according to the following equation26,27 ij n RT yz (B11 − V1*)p1sat ln γ13∞ = lnjjjj 3 sat zzzz − j VNp z RT 1 { k ij (2B12 − V1∞)J 3p yz 2 0z zz + jjjj zz j RT k {

(3)

where n3 is number of moles of D2EHIBA used for column packing; R is universal gas constant; T is column temperature; psat 1 is saturated vapor pressure of solute 1 at temperature T and is computed using Antoine equation; and Antoine coefficients are reported elsewhere.28 B11 is the second virial coefficient of pure solute 1, and B12 is the mixed second virial coefficient for solute and mobile phase interaction. B11 and B12 have been estimated using the McGlashan and Potter equation,29 shown below as B /Vc = 0.430 − 0.886(Tc/T ) − 0.694(Tc/T )2 − 0.0375(v − 1)(Tc/T )4.5

(4)

where “v” refers to the number of carbon atoms of the solute molecule and its value for helium is one. The Hudson and McCoubrey combining rules30,31 were used for the computation of values of mixed critical temperature (Tc12) and mixed critical volume (Vc12) of solutes and mobile phase and are c c c 1/2 T12 = (T11 T22)

c c 2(I1I2)1/2 26V11 + V 22 c 1/3 c 1/3 6 (I1 + I2) [(V11 ) + (V 22 ) ]

1 c 1/3 c 1/3 3 [(V11 ) + (V 22 ) ] 8

1 (ν1 + ν2) 2

Vc/(cm3 mol−1)

I/eV

n-pentane n-hexane n-heptane n-octane n-nonane n-decane n-undecane cyclohexane 1-hexene 1-heptene 1-octene 1-decene benzene toluene ethylbenzene n-propylbenzene n-butylbenzene p-xylene m-xylene dichloromethane trichloromethane tetrachloromethane acetone 3-hexanone 2-heptanone acetonitrile formaldehyde ethyl acetate 2,2,4-trimethylpentane 2-methylpentane helium

469.70 507.40 540.30 568.80 594.70 617.90 638.76 553.54 504.03 537.20 562.16 615.00 562.16 591.70 617.50 638.38 660.55 616.20 617.00 510.00 536.40 556.35 508.10 582.82 611.25 545.00 408.00 523.00 543.96 497.50 5.20

304 370 432 492 555 603 660 308 350 405 464 584 259 316 374 440 497 379 376 185 238 276 209 364 421 173 105 286 468 366.4 57.5

10.35 10.13 9.92 9.82 9.72 9.65 9.56 9.86 9.44 9.44 9.25 9.42 9.25 9.56 8.77 8.71 8.69 8.44 8.56 11.32 11.37 11.47 9.70 9.12 10.12 12.20 10.88 10.01 9.86 10.12 24.59

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RESULTS AND DISCUSSION The activity coefficients at infinite dilution obtained from net retention volume of solute are given in Table 3. There is a considerable difference between the values of activity coefficients at infinite dilution of these solutes in D2EHIBA. The availability of π electron clouds of the amidic group and dipole moment of D2EHIBA enhances the attractive interaction of D2EHIBA with the solutes. D2EHIBA contains CO and N−C dipoles arising from covalent bonding between strong electronegative oxygen and weak electronegative nitrogen and electro-neutral carbon atoms. The strong electronegativity of oxygen and π-bonding arrangement of the CO group allow them to act as relatively more polar, and the less electronegativity of nitrogen allows the N−C group to act as relatively less polar. D2EHIBA seems to have dual polar groups as reported elsewhere32 and dual nature of the stationary phase. The activity coefficients at infinite dilution of homologous series of solute increase with increasing carbon atoms in the alkyl chain. It indicates that the intermolecular interactions between D2EHIBA and n-alkane and the 1-alkene and alkylbenzene homologue become weak with increasing number of −CH2− groups incorporated with molecular

(5)

(6)

and ν=

Tc/K

D2EHIBA, vapor pressure of solute at column temperature, and inlet and outlet pressure all have experimental errors. The uncertainties associated with flow rate, D2EHIBA loading, and γ∞ 13 measurements are reported in Table 3.

where I is the ionization potential. The combining rule was used to compute mixed critical volume and is c V12 =

compounds

(7)

The critical constants and ionization potential of the solutes and the mobile phase used in the computation are given in Table 2. The saturated molar volume of solute (V1*) was computed using the modified Racket equation. Partial molar volume of solute at infinite dilution (V∞ 1 ) has been assumed to be equal to V1*. The values of vapor pressure, Psat 1 , molar volume, V1*, and second virial coefficients (B11 and B12) used in eq 3 at column temperatures are given in the Supporting Information as Table S3. Experimental Uncertainties. Column temperature, retention time of solutes and air, outlet flow rate, mass of C



Article

a,b Table 3. Experimental Activity Coefficients at Infinite Dilution (γ∞ 13) of Solutes as a Function of Temperature T

T/K solutes

323.15

333.15

343.15

353.15

363.15

373.15

n-pentane n-hexane n-heptane n-octane n-nonane n-decane n-undecane cyclohexane 1-hexene 1-heptene 1-octene 1-decene benzene toluene ethylbenzene n-propylbenzene n-butylbenzene p-xylene m-xylene dichloromethane trichloromethane tetrachloromethane acetone 3-hexanone 2-heptanone acetonitrile formaldehyde ethyl acetate 2,2,4-trimethylpentane 2-methylpentane

0.795 1.906 4.367 11.946 18.516 26.442 39.248 2.769 1.768 4.021 7.522 24.332 2.555 5.105 11.316 17.832 24.441 11.586 11.836 0.608 1.154 1.935 0.901 8.641 13.773 1.465 0.056 1.425 4.259 1.107

0.676 1.534 3.488 8.346 16.033 22.717 35.861 2.150 1.371 2.889 6.088 19.382 2.005 4.245 8.751 14.741 20.722 9.012 9.275 0.506 0.966 1.603 0.745 6.419 10.585 1.213 0.052 1.215 3.330 0.938

0.544 1.259 2.779 6.036 13.704 18.269 31.519 1.740 1.173 2.311 4.860 16.770 1.646 3.253 6.776 11.515 17.499 6.896 7.198 0.410 0.746 1.222 0.596 4.881 8.158 1.030 0.048 0.985 2.595 0.768

0.457 1.016 2.316 4.545 11.773 15.244 27.520 1.414 0.957 1.801 3.756 13.994 1.367 2.501 4.964 9.178 14.964 5.200 5.331 0.339 0.586 0.935 0.465 3.743 6.202 0.861 0.044 0.870 2.089 0.639

0.382 0.845 2.022 3.359 9.798 12.184 25.468 1.183 0.789 1.250 2.941 11.072 1.152 1.877 3.902 7.334 12.476 3.753 4.126 0.273 0.463 0.727 0.375 2.857 5.001 0.718 0.041 0.700 1.737 0.525

0.324 0.717 1.714 2.631 8.672 9.895 22.676 0.966 0.678 0.974 2.205 9.868 0.954 1.458 2.883 5.725 10.554 2.889 3.138 0.225 0.372 0.581 0.294 2.152 4.041 0.568 0.037 0.566 1.291 0.428

Pressure p = 0.1 MPa. bStandard uncertainties u are u(T) = 0.1 K, u(m) = 0.0001 g, u(U0) = 0.9 mL/min, and u(tR − t0) = (0.001−0.01) min, and relative uncertainties u are ur(γ∞ 13) = 0.05. a

structure. n-Undecane exhibited the highest value of activity coefficients at infinite dilution in the n-alkane homologous series. The highest value of activity coefficients at infinite dilution is for n-undecane, indicating weak interactions of nundecane with D2EHIBA. For 2,2,4-trimethylpentane and 2methylpentane, branching in the alkane skeleton reduces the γ∞ 13 values in comparison with the corresponding linear alkane. For aromatic compounds, the γ∞ 13 increases with increasing carbon number of the alkyl component of the side chain on the benzene ring. It signifies weak interaction with D2EHIBA. The activity coefficients at infinite dilution values for solutes with the same number of carbon atoms are in the order of γ∞ 1‑hexene < ∞ ∞ γ∞ n‑hexane < γbenzene < γcyclohexane. It can be due to the inclusion of localized and delocalized π-electrons and ring structure incorporated with molecular structure. The localized πelectrons of 1-hexene can interact strongly with more polar functional group (CO) of D2EHIBA. It results in the lowest ∞ value of γ∞ 13. The γ13 values for benzene are lower than that for cyclohexane due to the preferred attractive interactions between six π-delocalized electrons in benzene and the C O group of D2EHIBA. This behavior indicates that benzene has better solubility in D2EHIBA than cyclohexane. It can be seen that cyclohexane exhibits higher γ∞ 13 values as compared to n-hexane, which indicates weaker interactions with D2EHIBA. The preferred attractive interaction is between the less polar (N−C) group and cyclohexane or the steric effect caused by

cyclization of structure. The solutes with polar functional groups have higher solubility due to the preferred attractive interactions with polar D2EHIBA. It is reflected in the value of ∞ γ∞ 13 for polar solutes. The γ13 values of chloromethanes increase with increasing chlorine atom. This reveals that the polarity of chloromethane decreases with increasing chlorine atom. The polar solutes interact quite strongly with D2EHIBA, resulting in lower value of γ∞ 13 than the nonpolar solute. The lowest value of γ∞ 13 reveals the stronger interaction between D2EHIBA and polar solute. The activity coefficients at infinite dilution of all solutes decreased as temperature increased. The high value of activity coefficients at infinite dilution for higher homologue indicates low solubility in D2EHIBA. Figures 1−5 depict the linear relationship between ln γ∞ 13 and 1/T (K) for 30 solutes in D2EHIBA. The activity coefficients at infinite dilution for each solute in D2EHIBA were computed at T = 298.15 K using experimental values. These values have been fitted by simple linear regression as ln γ13∞ = a +

b (T /K)

(8)

The values of slope, intercept, correlation coefficient, and natural logarithm of activity coefficients at infinite dilution at 298.15 K (ln γ∞ 13, 298.15 K) and the partial molar excess enthalpies (HE,∞ 1 ) for each solute are given in Table 4. The partial molar excess enthalpies represent the enthalpy change D



Article

Figure 1. Plots of ln δ∞ 13 for n-alkanes vs 1/T: ■, n-pentane; ●, nhexane; ▲, n-heptane; ▼, n-octane; ⧫, n-nonane; ◀, n-decane; ▶, nundecane.

Figure 4. Plots of ln δ∞ 13 for benzene, toluene, ethylbenzene, npropylbenzene, n-butylbenzene, 2-methylpentane, and 2,2,4-trimethylpentane vs 1/T: ■, benzene; ●, toluene; ▲, ethylbenzene; ▼, npropylbenzene; ⧫, n-butylbenzene; ◀, 2-methylpentane; ▶, 2,2,4trimethylpentane.

Figure 2. Plots of ln δ∞ 13 for solutes with the same number of carbon atoms vs 1/T: ■, n-hexane; ●, 1-hexene; ▲, benzene; ▼, cyclohexane.

Figure 5. Plots of ln δ∞ 13 for p-xylene, m-xylene, ethyl acetate, 3hexanone, 2-heptanone, dichloromethane, trichloromethane, and tetrachloromethane vs 1/T: ■, p-xylene; ●, m-xylene; ▲, ethyl acetate; ▼, 3-hexanone; ⧫, 2-heptanone; ◀, dichloromethane; ▶, trichloromethane; ⎔, tetrachloromethane.

elsewhere33 for N-substituted amides. The steep increase in magnitude was observed for n-octane. It may be contributed by the size of alkyl chains of solute, and disubstituents incorporated with the N,N′-diamide moiety are the same. ∞ The plots of ln γ13 versus the carbon number of a homologous series of solutes (n-alkanes, 1-alkenes, alkylbenzenes, and ketones) at 353.15 K are depicted in Figure 6. It is observed that for all classes of solutes the ln γ∞ 13 values increase with an increase in carbon number. This indicates the decreased solubility or interaction of more hydrophobic solutes (increase in carbon number) with the D2EHIBA. The selectivity values at infinite dilution indicate suitability of a solvent for separating mixtures of solute i and j. The selectivity values at 323.15, 343.15, and 363.15 K (S∞ ij ) for different separation mixture (solute i/solute j) are computed from the ratio of the γ∞ 13 values through the following eq 9

Figure 3. Plots of ln δ∞ 13 for 1-alkenes, acetone, acetonitrile, and formaldehyde vs 1/T: ■, 1-hexene; ●, 1-heptene; ▲, 1-octene; ▼, 1decene; ⧫, acetone; ◀, acetonitrile; ▶, formaldehyde.

for the transfer of one mole of solute from the (infinitely diluted) ideal solution to the real one. The HE,∞ is positive 1 which indicates a tendency toward more ideal behavior at increasing temperatures. The general trend in ΔΗΕ,∞ for these 1 N,N″-disubstituted amides is similar to the one reported

∞ = S12

E

γi∞ γj∞

(9) DOI: 10.1021/acs.jced.8b00635 J. Chem. Eng. Data XXXX, XXX, XXX−XXX


Article

E,∞ Table 4. Activity Coefficients (γ∞ 13,298.15 K,0.1 MPa) and Partial Molar Excess Enthalpies at Infinite Dilution (H1 ) Using Linear Dependence Equation 8 Values of HE,∞ Obtained from Equation 8 and Standard Deviation 2σ 1

solutes

a ∞ γ13,298.15 K

n-pentane n-hexane n-heptane n-octane n-nonane n-decane n-undecane cyclohexane 1-hexene 1-heptene 1-octene 1-decene benzene toluene ethylbenzene n-propylbenzene n-butylbenzene p-xylene m-xylene dichloromethane trichloromethane tetrachloromethane acetone 3-hexanone 2-heptanone acetonitrile formaldehyde ethyl acetate 2,2,4-trimethylpentane 2-methylpentane

1.433 3.553 7.665 30.449 30.602 51.274 56.339 5.246 3.167 9.658 16.974 42.987 4.624 12.113 27.612 37.813 42.050 29.287 28.434 1.167 2.488 4.401 1.903 20.754 30.041 2.677 0.072 2.599 8.926 2.071

b

HE,∞ /kJ mol−1 1

a −7.0 −6.7 −5.5 −8.9 −2.9 −4.1 −0.5 −6.8 −6.5 −9.1 −7.1 −3.6 −6.3 −7.8 −7.8 −5.5 −3.0 −7.9 −7.4 −7.9 −8.4 −8.5 −8.4 −8.1 −6.6 −6.5 −5.7 −6.4 −7.2 −6.9

18.269 19.674 18.653 30.353 15.517 19.898 11.185 20.833 19.088 28.307 24.492 18.263 19.505 25.643 27.371 22.880 16.810 28.168 26.789 20.028 23.182 24.766 22.606 27.607 24.818 18.530 7.819 18.268 23.301 19.061

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

b 0.1 0.1 0.2 0.1 0.1 0.3 0.1 0.1 0.1 0.0 0.3 0.3 0.1 0.4 0.3 0.3 0.1 0.3 0.3 0.2 0.3 0.3 0.3 0.2 0.1 0.3 0.1 0.3 0.3 0.2

2197 2366 2243 3650 1866 2397 1347 2505 2295 3404 2945 2196 2346 3084 3292 2752 2021 3388 3222 2408 2788 2978 2719 3320 2985 2228 940 2197 2802 2292

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

45 22 67 37 43 11 48 29 54 17 14 82 32 14 11 94 53 13 99 65 95 99 99 60 34 99 39 89 95 77

2σ

R

0.0316 0.0132 0.0465 0.0262 0.0384 0.0733 0.0333 0.0205 0.0376 0.0119 0.0940 0.0571 0.0226 0.0651 0.0735 0.0655 0.0368 0.0874 0.0696 0.0456 0.0633 0.0726 0.0694 0.0418 0.0238 0.0697 0.0548 0.0772 0.0622 0.0539

0.9991 0.9998 0.9982 0.9998 0.9982 0.9961 0.9975 0.9997 0.9989 0.9999 0.9958 0.9982 0.9996 0.9994 0.9979 0.9976 0.9986 0.9972 0.9981 0.9951 0.9977 0.9975 0.9973 0.9994 0.9997 0.9959 0.9965 0.9949 0.9977 0.9977

solutes determined in this work. bThe value for the partial molar excess enthalpy ÄÅ ∞ É Ñ E, ∞ ÅÅ ∂ln γ13 ÑÑÑ = H1 . at infinite dilution (HE,∞ ÅÅ ∂(1 / T ) ÑÑ 1 ) was obtained from the slope of a straight line derived from equation Å R ÅÇ ÑÖ Computed using the linear dependence of ln γ13∞ = a +

a

b for (T / K )

Table 5. Selectivity, S∞ ij , at Infinite Dilution at T = (323.15, 343.15, and 363.15) K and Pressure p = 0.1 MPa separation mixture

323.15 K

343.15 K

363.15 K

cyclohexane/n-hexane benzene/n-hexane 1-hexene/n-hexane benzene/n-heptane 1-heptene/n-heptane 1-octene/n-octane ethylbenzene/n-octane 1-decene/n-decane n-butylbenzene/n-decane

1.444 1.332 0.923 0.583 0.920 0.629 0.947 0.924 1.004

1.372 1.298 0.925 0.590 0.773 0.805 1.122 0.917 0.957

1.334 1.350 0.925 0.568 0.618 0.875 1.161 0.908 1.023

hexane compounds by extractive distillation and solvent extraction.

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Figure 6. Plots of ln δ∞ 13 versus carbon number of n-alkanes, 1-alkenes, alkylbenzenes, and ketones at 353.15 K: ■, n-alkanes; ●, 1-alkenes; ▲, alkylbenzenes; ▼, ketones.

CONCLUSIONS Inverse gas−liquid chromatography offered a reliable and rapid method for determining activity coefficients at infinite dilution of solutes in D2EHIBA. The magnitude of the activity coefficient at infinite dilution of a homologous series of solutes in D2EHIBA investigated in this study increased with increasing −CH2− group. The magnitude of the activity coefficient of a solute depends upon the structure of solute and

and the values are given in Table 5. The selectivity value is dependent on the interaction between solute and D2EHIBA. The values are smaller than two. The S∞ ij values greater than one show the possibility of using D2EHIBA as a separating media for separating cyclohexane/n-hexane and benzene/nF



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structure of alkyl substituents incorporated with the amide moiety. The values of partial excess enthalpies at infinite dilution for same solutes were computed, and their magnitude depend upon the size of the solute and alkyl groups incorporated with the amide moiety.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jced.8b00635. 1 H NMR spectra (Table S1 and Figure S1) and 13C NMR spectra (Table S2 and Figure S2) for synthesis of D2EHIBA and computed vapor pressure, molar volume, and virial coefficients of solutes at column temperature T = (323.15 to 373.15) K (Table S3) (PDF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone (O): +914427480098. Fax (O): +914427480065. ORCID

K. Panneerselvam: 0000-0003-0273-8052 Notes

The authors declare no competing financial interest.

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