Volumetric and Acoustic Properties of Aqueous Solutions of

Article pubs.acs.org/jced

Volumetric and Acoustic Properties of Aqueous Solutions of Trifluoromethanesulfonate-Based Ionic Liquids at Several Temperatures Ernesto Vercher, Pablo J. Miguel, Francisco J. Llopis, A. Vicent Orchillés, and Antoni Martínez-Andreu* Departamento de Ingeniería Química, Escuela Técnica Superior de Ingeniería, Universitat de València, 46100 Burjassot, Valencia, Spain ABSTRACT: In this work, densities and sound velocities of three ionic liquids, 3-butyl-1-ethylimidazolium trifluoromethanesulfonate, 3-butyl-1methylimidazolium trifluoromethanesulfonate, and 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate, and their binary mixtures with water have been obtained at p = (101 ± 2) kPa and T = (278.15 to 338.15) K, covering the whole range of concentration. The isentropic compressibility and molar isentropic compression of pure components and mixtures have been calculated using the Newton−Laplace equation. Moreover, the excess molar volume and excess molar isentropic compression of mixtures have been then determined, and they have been fitted to temperature and composition by an extended Redlich− Kister equation. Optimal fitting parameters have been reported.

■

INTRODUCTION Ionic liquids (ILs) are salts having melting points below 100 °C, because its crystallization is prevented by its asymmetrical structure. ILs are made of a voluminous cation, such as quaternary ammonium, tetraalkylphosphonium, imidazolium, pyrrolidinium, pyridinium, and so forth, and an anion such as chloride, bromide, tetrafluoroborate, hexafluorophosphate, trifluoromethanesulfonate, alkyl sulfate, dicyanamide, and so forth. By modifying the anions, the cations, or their substituents, physical and chemical properties of ILs can be changed.1 Moreover, ILs present very interesting properties: they have a vapor pressure of practically zero, present electrical conductivity, and are excellent solvents so much for protic or aprotic polar substances as for nonpolar ones.2 Because of that, ILs are been used replacing volatile organic solvents in many industrial operations and as entrainers for liquid−liquid extraction3 and extractive distillation.4 In the last few years, many industrial applications have been reported, as catalysts for organic and organometallic synthesis,5,6 electrically conductive liquids in electrochemistry, thermofluids, lubricants, plasticizers, and so forth.2 ILs based in the trifluoromethanesulfonate anion have been proposed as entrainers for extractive distillation of some azeotropic aqueous mixtures.7−9 To clarify the nature of interactions between ILs and solvents as well as to design any technological processes, detailed knowledge on the physical, thermodynamic, and transport properties of ILs is required.10 However, the number of studies reported in the literature on physical properties of aqueous mixtures of ILs is limited, despite their great practical importance. © 2012 American Chemical Society

In the present work, the volumetric and acoustical properties of aqueous solutions of three ILs containing the trifluoromethanesulfonate ([triflate]) anion, 3-butyl-1-ethylimidazolium trifluoromethanesulfonate ([beim][triflate], CAS Registry No. 145022-48-6), 3-butyl-1-methylimidazolium trifluoromethanesulfonate ([bmim][triflate], CAS Registry No. 174899-66-2), and 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ([bmpyr][triflate], CAS Registry No. 367522-96-1) are reported, covering the entire range of concentrations, at temperatures from (278.15 to 338.15) K and a pressure of (101 ± 2) kPa. From these, values of the excess molar volume and excess molar isentropic compression have been calculated and fitted to polynomial equations. To our best knowledge, [emim][triflate] is the only [triflate]based IL of which the density11−13 and speed of sound12 of its aqueous solutions have been reported at several temperatures. Densities of [bmim][triflate] + water system have been reported by Ge et al.14 and Garcia-Miaja et al.13 However, these two papers present serious disagreements in the reported values of the excess molar volumes calculated from density measurements, so it seems advisable to study this system again. The density of the remainder aqueous systems and the speed of sound of all of the IL + water systems reported in this work have not been previously studied.

■

EXPERIMENTAL SECTION Materials. The ILs used in this work were [beim][triflate], [bmim][triflate], and [bmpyr][triflate]. Before use, they were Received: January 30, 2012 Accepted: June 20, 2012 Published: June 28, 2012 1953

dx.doi.org/10.1021/je300134c | J. Chem. Eng. Data 2012, 57, 1953−1963

Journal of Chemical & Engineering Data

Article

Apparatus and Procedure. The IL + water binary mixtures samples were prepared by weighing on a Mettler XP205 Delta Range analytical balance, which has a precision of 1·10−5 g, following the procedure reported in a previous work.12 Taking into account the mass of each component placed into the vial and the balance accuracy, the uncertainty in mole fractions of all of the samples was estimated to be in any case less than 0.00002. A digital vibrating-tube densimeter and speed of sound analyzer (Anton Paar DSA 5000) was used to measure the density, ρ, and the speed of sound, u, of pure components and binary mixtures. The apparatus maintains the temperature of the samples with an accuracy of 0.001 K. According to the supplier specifications, it was calibrated at 298.15 K with bidistilled water and dry air. Standard uncertainties of measurements were estimated to be less than 0.003 K for temperature, 0.007 kg·m−3 for density, and 0.05 m·s−1 for speed of sound.

kept at 0.2 kPa for 24 h to reduce its water mass fraction below 0.05 %. The water used in binary systems was supplied by Merck, chromatography grade (residue on evaporating < 5 g·m−3), and it was used as purchased. In Table 1, the chemical specifications of the used materials are reported. Table 1. Specifications of Chemical Samples mass fraction purity

chemical name

source

water [beim] [triflate]a [bmim] [triflate]b [bmpyr] [triflate]c

Merck Solvent Innovation Solvent Innovation IoLiTec

d > 0.98 > 0.98 > 0.99

purification method none vacuum desiccation vacuum desiccation vacuum desiccation

final water mass fraction

analysis method

< 0.0005

KFe

< 0.0005

KFe

< 0.0005

KFe

a [beim][triflate] = 3-butyl-1-ethylimidazolium trifluoromethanesulfonate. b[bmim][triflate] = 3-butyl-1-methylimidazolium trifluoromethanesulfonate. c[bmpyr][triflate] = 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate. dConductivity at 298.15 K: σ ≤ 1 μS·cm−1. eKF = Karl Fischer titration.

■

RESULTS AND DISCUSSION Molar volume, Vm, is defined as

Table 2. Density ρ, Molar Volume Vm, Speed of Sound u, Isentropic Compressibility κS, Molar Isentropic Compression KS,m, Isobaric Molar Heat Capacity Cp, and Isobaric Thermal Expansivity αp of Pure Water, [beim][triflate], [bmim][triflate], and [bmpyr][triflate] at Several Temperaturesa T K

ρ kg·m

106 Vm −3

m ·mol 3

−1

κS

u m·s

−1

TPa

−1

1015 KS,m

Cp

αp

m ·mol−1·Pa−1

J·mol−1·K−1

kK−1

8.843 8.386 8.083 7.890 7.780 7.741 7.763

75.93b 75.60b 75.38b 75.27b 75.24b 75.27b 75.36b

0.0160c 0.1509c 0.2572c 0.3457c 0.4225c 0.4910c 0.5539c

91.721 96.146 100.652 105.326 110.190 115.263 120.540

469.58d 475.71d 481.84d 487.96d 494.09d 500.22d 506.34d

0.629 0.622 0.618 0.616 0.617 0.620 0.626

84.482 88.361 92.378 96.542 100.877 105.381

420.95e 426.65e 432.36e 438.07e 443.78e 449.49e

0.615 0.611 0.608 0.608 0.609 0.613

79.194 83.120 86.984 90.908 94.961 99.154 103.479

431.84d 434.85d 437.67d 440.30d 442.77d 445.09d 447.27d

0.605 0.592 0.583 0.577 0.575 0.577 0.582

3

Water 278.15 288.15 298.15 308.15 318.15 328.15 338.15

999.99 999.12 997.06 994.05 990.22 985.70 980.56

18.016 18.032 18.069 18.124 18.194 18.277 18.373

1427.35 1466.98 1497.34 1520.26 1536.76 1547.68 1553.61

278.15 288.15 298.15 308.15 318.15 328.15 338.15

1278.02 1269.97 1262.21 1254.44 1246.71 1239.01 1231.35

236.554 238.052 239.517 241.000 242.494 244.002 245.518

1420.57 1396.28 1373.07 1350.57 1328.61 1307.12 1286.13

288.15 298.15 308.15 318.15 328.15 338.15

1304.56 1296.67 1288.78 1280.95 1273.16 1265.44

220.987 222.330 223.692 225.060 226.436 227.819

1416.02 1393.01 1370.73 1349.04 1327.81 1307.05

278.15 288.15 298.15 308.15 318.15 328.15 338.15

1267.23 1259.74 1252.26 1245.09 1237.94 1230.81 1223.73

229.895 231.263 232.643 233.983 235.335 236.698 238.068

1513.53 1486.14 1461.43 1437.77 1414.89 1392.66 1371.14

490.84 465.09 447.34 435.27 427.62 423.54 422.51 [beim][triflate] 387.74 403.89 420.23 437.04 454.40 472.38 490.96 [bmim][triflate] 382.29 397.43 412.97 428.96 445.50 462.57 [bmpyr][triflate] 344.48 359.42 373.89 388.53 403.51 418.91 434.66

a Standard uncertainties u are u(T) < 0.003 K, u(ρ) = 7·10−3 kg·m−3, u(u) = 0.05 m·s−1, and the combined standard uncertainties Uc are Uc(Vm) < 7·10−9 m3·mol−1, Uc(κS) < 0.05 TPa−1, Uc(KS,m) < 5·10−18 m3·mol−1·Pa−1, and Uc(αp) = 0.002 kK−1. bFrom ref 21. cFrom ref 15. dFrom ref 22. e Derived from refs 13, 23, and 24.

1954



Article

Table 3. Density ρ, Molar Volume Vm, Excess Molar Volume VmE, Speed of Sound u, Isentropic Compressibility κS, Molar Isentropic Compression KS,m, and Excess Molar Isentropic Compression KS,mE for the Binary System [beim][triflate] (1) + Water (2) at T = (278.15 to 338.15) Ka ρ

106 Vm −3

−1

106 VmE

m ·mol

m ·mol

0.00000 0.04992 0.10010 0.14982 0.19984 0.30128 0.40123 0.49597 0.60165 0.70071 0.85508 0.90059 1.00000

999.99 1120.13 1171.15 1199.88 1218.01 1239.57 1251.73 1259.25 1265.19 1269.28 1274.04 1275.29 1278.02

18.016 28.753 39.684 50.515 61.436 83.635 105.524 126.283 149.437 171.144 204.955 214.898 236.554

0.000 −0.171 −0.209 −0.244 −0.252 −0.222 −0.176 −0.121 −0.062 −0.003 0.070 0.068 0.000

0.00000 0.04992 0.10010 0.14982 0.19984 0.30128 0.40123 0.49597 0.60165 0.70071 0.85508 0.90059 1.00000

999.12 1114.86 1164.38 1192.37 1210.13 1231.45 1243.63 1251.19 1257.22 1261.36 1266.20 1267.39 1269.97

18.032 28.889 39.914 50.833 61.836 84.186 106.212 127.096 150.385 172.218 206.224 216.237 238.052

0.000 −0.125 −0.142 −0.163 −0.164 −0.133 −0.099 −0.059 −0.021 0.017 0.056 0.057 0.000

0.00000 0.04992 0.10010 0.14982 0.19984 0.30128 0.40123 0.49597 0.60165 0.70071 0.85508 0.90059 1.00000

997.06 1109.08 1157.27 1184.63 1202.11 1223.27 1235.48 1243.13 1249.23 1253.44 1258.37 1259.57 1262.21

18.069 29.040 40.160 51.165 62.249 84.749 106.912 127.921 151.347 173.307 207.507 217.580 239.517

0.000 −0.083 −0.077 −0.083 −0.074 −0.038 −0.009 0.021 0.044 0.068 0.082 0.077 0.000

0.00000 0.04992 0.10010 0.14982 0.19984 0.30128 0.40123 0.49597 0.60165 0.70071 0.85508 0.90059 1.00000

994.05 1102.81 1149.85 1176.70 1193.95 1215.04 1227.32 1235.04 1241.24 1245.51 1250.54 1251.76 1254.44

18.124 29.205 40.419 51.510 62.674 85.323 107.623 128.758 152.321 174.410 208.806 218.938 241.000

0.000 −0.045 −0.016 −0.007 0.011 0.051 0.074 0.094 0.104 0.115 0.104 0.094 0.000

3

κS

u

−1

kg·m

x1

3

m·s

−1

T = 278.15 K 1427.35 1523.96 1521.29 1514.71 1505.62 1484.58 1467.68 1455.38 1444.88 1436.19 1427.95 1424.75 1420.57 T = 288.15 K 1466.98 1527.08 1513.55 1500.21 1487.08 1462.69 1444.71 1431.99 1421.05 1412.43 1403.70 1400.65 1396.28 T = 298.15 K 1497.34 1526.48 1503.04 1484.06 1467.74 1440.78 1421.98 1409.02 1397.88 1389.35 1380.49 1377.53 1373.07 T = 308.15 K 1520.26 1522.46 1490.16 1466.44 1447.61 1418.65 1399.31 1386.26 1375.06 1366.65 1357.84 1355.01 1350.57

1955

TPa

1015 KS,m −1

−1

1015 KS,mE −1

m ·mol ·Pa 3

m ·mol−1·Pa−1 3

490.84 384.40 368.95 363.25 362.17 366.04 370.87 374.92 378.60 381.96 384.94 386.29 387.74

8.843 11.053 14.641 18.349 22.251 30.613 39.136 47.346 56.577 65.371 78.895 83.013 91.721

0.000 −2.400 −3.242 −3.810 −4.139 −4.229 −3.938 −3.480 −2.859 −2.113 −1.102 −0.667 0.000

465.09 384.64 374.90 372.64 373.68 379.56 385.26 389.76 393.89 397.40 400.82 402.19 403.89

8.386 11.112 14.964 18.942 23.107 31.954 40.919 49.537 59.235 68.439 82.659 86.968 96.146

0.000 −2.046 −2.822 −3.334 −3.628 −3.720 −3.482 −3.095 −2.550 −1.906 −1.004 −0.616 0.000

447.34 386.95 382.49 383.28 386.15 393.81 400.29 405.18 409.66 413.31 416.99 418.38 420.23

8.083 11.237 15.361 19.610 24.037 33.374 42.796 51.831 62.000 71.629 86.529 91.032 100.652

0.000 −1.792 −2.498 −2.955 −3.214 −3.296 −3.090 −2.755 −2.268 −1.699 −0.901 −0.550 0.000

435.27 391.21 391.65 395.19 399.68 408.94 416.12 421.34 426.09 429.87 433.72 435.11 437.04

7.890 11.425 15.830 20.356 25.049 34.892 44.784 54.250 64.902 74.973 90.563 95.261 105.326

0.000 −1.601 −2.239 −2.644 −2.870 −2.935 −2.750 −2.457 −2.018 −1.507 −0.803 −0.489 0.000



Article

Table 3. continued ρ

106 Vm

106 VmE

u

κS

1015 KS,m

1015 KS,mE

x1

kg·m−3

m3·mol−1

m3·mol−1

m·s−1

TPa−1

m3·mol−1·Pa−1

m3·mol−1·Pa−1

0.00000 0.04992 0.10010 0.14982 0.19984 0.30128 0.40123 0.49597 0.60165 0.70071 0.85508 0.90059 1.00000

990.22 1096.10 1142.14 1168.57 1185.67 1206.74 1219.13 1226.96 1233.26 1237.61 1242.74 1243.97 1246.71

18.194 29.384 40.691 51.868 63.112 85.910 108.346 129.607 153.307 175.523 210.117 220.308 242.494

0.000 −0.007 0.044 0.068 0.094 0.138 0.155 0.166 0.163 0.161 0.128 0.111 0.000

427.62 397.40 402.38 408.42 414.35 425.03 432.79 438.29 443.29 447.11 451.04 452.43 454.40

7.780 11.677 16.373 21.184 26.151 36.514 46.891 56.805 67.960 78.477 94.772 99.675 110.190

0.000 −1.448 −2.021 −2.375 −2.569 −2.613 −2.445 −2.184 −1.780 −1.330 −0.712 −0.428 0.000

0.00000 0.04992 0.10010 0.14982 0.19984 0.30128 0.40123 0.49597 0.60165 0.70071 0.85508 0.90059 1.00000

985.70 1088.96 1134.15 1160.26 1177.26 1198.39 1210.91 1218.87 1225.30 1229.73 1234.98 1236.23 1239.01

18.277 29.576 40.978 52.240 63.563 86.508 109.081 130.467 154.302 176.648 211.437 221.688 244.002

0.000 0.031 0.104 0.143 0.177 0.224 0.235 0.236 0.218 0.203 0.146 0.125 0.000

423.54 405.48 414.67 423.00 430.28 442.14 450.40 456.09 461.19 465.08 469.00 470.42 472.38

7.741 11.992 16.992 22.097 27.350 38.249 49.130 59.504 71.162 82.156 99.163 104.286 115.263

0.000 −1.320 −1.829 −2.133 −2.291 −2.315 −2.157 −1.926 −1.569 −1.159 −0.635 −0.369 0.000

0.00000 0.04992 0.10010 0.14982 0.19984 0.30128 0.40123 0.49597 0.60165 0.70071 0.85508 0.90059 1.00000

980.56 1081.43 1125.92 1151.76 1168.74 1189.99 1202.68 1210.79 1217.37 1221.89 1227.27 1228.53 1231.35

18.373 29.782 41.278 52.625 64.026 87.119 109.827 131.337 155.308 177.782 212.765 223.077 245.518

0.000 0.070 0.166 0.219 0.261 0.311 0.316 0.307 0.273 0.247 0.164 0.139 0.000

422.51 415.40 428.50 438.93 447.50 460.30 468.92 474.72 479.86 483.78 487.60 488.96 490.96

7.763 12.372 17.687 23.099 28.652 40.101 51.500 62.348 74.527 86.008 103.745 109.076 120.540

0.000 −1.205 −1.651 −1.904 −2.020 −2.025 −1.877 −1.674 −1.358 −0.988 −0.557 −0.326 0.000

T = 318.15 K 1536.76 1515.17 1475.10 1447.51 1426.70 1396.32 1376.70 1363.66 1352.47 1344.32 1335.68 1332.96 1328.61 T = 328.15 K 1547.68 1504.91 1458.18 1427.43 1405.04 1373.79 1354.08 1341.21 1330.27 1322.30 1313.97 1311.32 1307.12 T = 338.15 K 1553.61 1491.99 1439.70 1406.44 1382.75 1351.16 1331.61 1319.01 1308.37 1300.65 1292.70 1290.24 1286.13

Standard uncertainties u are u(T) < 0.003 K, u(ρ) = 7·10−3 kg·m−3, u(u) = 0.05 m·s−1, and the combined standard uncertainties Uc are Uc(x1) < 2·10−5, Uc(Vm) < 7·10−9 m3·mol−1, Uc(VmE) < 1·10−8 m3·mol−1, Uc(κS) < 0.05 TPa−1, Uc(KS,m) < 5·10−18 m3·mol−1·Pa−1, and Uc(KS,mE) < 7·10−18 m3·mol−1·Pa−1. a

Vm =

Mm ρ

(x1M1o

Molar isentropic compression, KS,m, is defined from the isentropic compressibility as

(1)

⎛ ∂V ⎞ Vm2 KS ,m = −⎜ m ⎟ = Vm·κS = M m ·u2 ⎝ ∂p ⎠S

x2M2o)

with Mm = + being the molar mass of the mixture, Moi that of pure component i, and xi its mole fraction. Isentropic compressibility, κS, is defined as 1 ⎛ ∂V ⎞ 1 ⎛ ∂ρ ⎞ κS = − ⎜ m ⎟ = ⎜ ⎟ Vm ⎝ ∂p ⎠ ρ ⎝ ∂p ⎠ S S

The combined standard uncertainties are less than 7·10−9 m ·mol−1 for molar volume, 0.05 TPa−1 for the isentropic compressibility, and 5·10−18 m3·mol−1·Pa−1 for the molar isentropic compression. Volumetric Properties of Pure Liquids. In Table 2 we have reported density ρ and sound velocity u of pure components at T = (278.15 to 338.15) K. In this table, molar volume Vm, isentropic compressibility κS, and molar 3

(2)

and is given by the Newton−Laplace equation κS =

Vm 1 = 2 ρ·u M m ·u2

(4)

(3) 1956



Article

Table 4. Density ρ, Molar Volume Vm, Excess Molar Volume VmE, Speed of Sound u, Isentropic Compressibility κS, Molar Isentropic Compression KS,m, and Excess Molar Isentropic Compression KS,mE for the Binary System [bmim][triflate] (1) + Water (2) at T = (288.15 to 338.15) Ka ρ

106 Vm −3

−1

106 VmE

m ·mol

m ·mol

0.00000 0.05002 0.09974 0.14991 0.30127 0.39941 0.49729 0.59991 0.69882 0.89532 1.00000

999.12 1122.78 1178.77 1211.09 1257.47 1272.13 1281.71 1289.22 1294.59 1302.01 1304.56

18.032 28.086 38.152 48.330 79.081 99.019 118.920 139.740 159.810 199.690 220.987

0.000 −0.097 −0.122 −0.126 −0.096 −0.075 −0.039 −0.046 −0.050 −0.052 0.000

0.00000 0.05002 0.09974 0.14991 0.30127 0.39941 0.49729 0.59991 0.69882 0.89532 1.00000

997.06 1116.95 1171.65 1203.38 1249.32 1263.98 1273.59 1281.16 1286.57 1294.08 1296.67

18.069 28.233 38.383 48.640 79.597 99.659 119.678 140.619 160.806 200.914 222.330

0.000 −0.053 −0.058 −0.049 −0.010 0.006 0.032 0.013 −0.004 −0.034 0.000

0.00000 0.05002 0.09974 0.14991 0.30127 0.39941 0.49729 0.59991 0.69882 0.89532 1.00000

994.05 1110.67 1164.25 1195.48 1241.10 1255.79 1265.46 1273.10 1278.56 1286.15 1288.78

18.124 28.393 38.627 48.962 80.124 100.308 120.447 141.509 161.813 202.152 223.692

0.000 −0.013 0.001 0.021 0.068 0.078 0.096 0.064 0.034 −0.021 0.000

0.00000 0.05002 0.09974 0.14991 0.30127 0.39941 0.49729 0.59991 0.69882 0.89532 1.00000

990.22 1103.96 1156.58 1187.40 1232.82 1247.58 1257.33 1265.05 1270.58 1278.27 1280.95

18.194 28.565 38.884 49.295 80.662 100.968 121.226 142.410 162.829 203.398 225.060

0.000 0.024 0.058 0.090 0.146 0.150 0.159 0.115 0.074 −0.007 0.000

0.00000 0.05002 0.09974 0.14991 0.30127 0.39941 0.49729 0.59991

985.70 1096.85 1148.65 1179.14 1224.48 1239.35 1249.21 1257.03

18.277 28.750 39.152 49.640 81.212 101.639 122.014 143.318

0.000 0.061 0.114 0.158 0.222 0.221 0.221 0.165

3

κS

u

−1

kg·m

x1

3

m·s

−1

T = 288.15 K 1466.98 1539.45 1524.84 1510.43 1474.64 1459.03 1447.64 1438.01 1431.57 1420.49 1416.02 T = 298.15 K 1497.34 1538.23 1514.34 1494.79 1453.80 1437.31 1425.50 1415.65 1408.80 1397.71 1393.01 T = 308.15 K 1520.26 1533.54 1501.62 1477.87 1432.73 1415.58 1403.54 1393.57 1386.55 1375.51 1370.73 T = 318.15 K 1536.76 1525.78 1486.94 1459.75 1411.43 1393.85 1381.69 1371.71 1364.70 1353.78 1349.04 T = 328.15 K 1547.68 1515.23 1470.56 1440.52 1389.85 1372.06 1359.91 1350.07 1957

TPa

1015 KS,m −1

−1

1015 KS,mE −1

m ·mol ·Pa 3


465.09 375.81 364.86 361.93 365.70 369.27 372.30 375.10 376.92 380.64 382.29

8.386 10.555 13.920 17.492 28.920 36.564 44.274 52.417 60.235 76.009 84.482

0.000 −2.004 −2.654 −3.040 −3.264 −3.053 −2.709 −2.254 −1.825 −0.690 0.000

447.34 378.38 372.18 371.91 378.72 382.97 386.40 389.48 391.62 395.55 397.43

8.083 10.683 14.286 18.090 30.145 38.166 46.244 54.769 62.975 79.472 88.361

0.000 −1.723 −2.304 −2.644 −2.848 −2.676 −2.386 −1.999 −1.618 −0.636 0.000

435.27 382.85 380.92 382.99 392.52 397.39 401.15 404.46 406.82 410.94 412.97

7.890 10.870 14.714 18.752 31.451 39.861 48.317 57.236 65.829 83.073 92.378

0.000 −1.503 −2.021 −2.320 −2.499 −2.354 −2.110 −1.777 −1.445 −0.587 0.000

427.62 389.10 391.06 395.23 407.18 412.57 416.61 420.11 422.59 426.86 428.96

7.780 11.115 15.206 19.483 32.844 41.657 50.504 59.828 68.810 86.822 96.542

0.000 −1.326 −1.785 −2.044 −2.192 −2.068 −1.859 −1.572 −1.288 −0.535 0.000

423.54 397.10 402.58 408.69 422.78 428.61 432.86 436.46

7.741 11.417 15.762 20.287 34.335 43.563 52.815 62.552

0.000 −1.177 −1.581 −1.799 −1.913 −1.804 −1.625 −1.383



Article


106 Vm

106 VmE

u

κS

1015 KS,m

1015 KS,mE

x1

kg·m−3

m3·mol−1

m3·mol−1

m·s−1

TPa−1

m3·mol−1·Pa−1

m3·mol−1·Pa−1

0.69882 0.89532 1.00000

1262.64 1270.44 1273.16

163.853 204.651 226.436

0.111 0.005 0.000

439.00 443.35 445.50

71.932 90.731 100.877

−1.145 −0.488 0.000

0.00000 0.05002 0.09974 0.14991 0.30127 0.39941 0.49729 0.59991 0.69882 0.89532 1.00000

980.56 1089.38 1140.47 1170.71 1216.08 1231.09 1241.08 1249.02 1254.72 1262.66 1265.44

18.373 28.947 39.433 49.997 81.773 102.321 122.813 144.238 164.887 205.913 227.819

0.000 0.098 0.170 0.226 0.300 0.293 0.285 0.217 0.150 0.019 0.000

422.51 406.75 415.49 423.46 439.37 445.44 449.90 453.51 456.32 460.66 462.57

7.763 11.774 16.384 21.172 35.928 45.578 55.253 65.413 75.241 94.856 105.381

0.000 −1.046 −1.396 −1.569 −1.644 −1.557 −1.397 −1.199 −0.964 −0.389 0.000

T = 328.15 K 1343.16 1332.45 1327.81 T = 338.15 K 1553.61 1502.26 1452.70 1420.26 1368.06 1350.40 1338.27 1328.69 1321.58 1311.19 1307.05


isentropic compression KS,m calculated from experimental density and speed of sound values are also reported. As far as the [bmim][triflate] is concerned, measurements could not be made at T = 278.15 K because that IL is solid at this temperature. As expected, density decreases and molar volume increases when the temperature increases for all of the components. The speed of sound of water varies with the temperature in an anomalous way. It increases with temperature, although, according to literature,15 this happens only until 347 K since then it decreases. Therefore, the isentropic compressibility and the molar isentropic compression for water decrease as temperature increases, reaching minimum values at T = (337 and 329) K, respectively. On the contrary, the speed of sound of the ILs decreases when the temperature increases. Therefore, the isentropic compressibility and the molar isentropic compression for the ILs increase with temperature. Comparing the properties of [beim][triflate] and [bmim][triflate] with those reported for the [emim][triflate] by Vercher et al.,12 it can be observed that both the density and speed of sound decrease when the alkyl substituents size increases, whereas the isentropic compressibility and the molar isentropic compression obviously increase. For [beim][triflate], our measured values agree within 0.07 % with the only values found in the literature reported by Vercher et al.16 at 298.15 K. For [bmim][triflate] our density data agree with those of Jacquemin et al.,17 Garcia-Miaja et al.,13 Zech et al.,18 and Klomfar et al.19 within 0.06 %, and our speed of sound values agree with those of Garcia-Miaja et al.13 within 0.07 %. For [bmpyr][triflate], only Gaciño et al.20 have reported density data, which are in agreement with our data within 0.006 %. To calculate the excess properties of mixtures we need to know the isobaric thermal expansivity αp of pure components. Values of the isobaric thermal expansivity of water have been taken from Kell.15 For the ILs, we have correlated the variation of density with temperature to third-order polynomials, and by using the expression

αp =

1 ⎛ ∂Vm ⎞ 1 ⎛ ∂ρ ⎞ ⎜ ⎟ =− ⎜ ⎟ Vm ⎝ ∂T ⎠ p ρ ⎝ ∂T ⎠ p

(5)

the isobaric thermal expansivity αp of the ILs at each temperature was obtained. The combined standard uncertainty for this parameter was estimated to be less than 0.002 kK−1. For [bmpyr][triflate], our isobaric thermal expansivity values and those reported by Gaciño et al.20 agree within 0.5 %. The isobaric molar heat capacity Cp of pure components is also needed to calculate the excess properties. A correlation proposed in the Daubert and Danner data compilation21 has been used to estimate the isobaric molar heat capacity of water at each temperature. The method proposed by Valderrama et al.22 has been used to obtain Cp values for [beim][triflate] and [bmpyr][triflate], whereas for [bmim][triflate], Cp values have been obtained with a fitting equation from experimental data of Diedrichs and Gmehling,23 Garcia-Miaja et al.,13 and Paulechka et al.24 In Table 2, the isobaric thermal expansivity αp and the isobaric molar heat capacity Cp values of pure components at each temperature have been reported. Volumetric Properties of Liquid Mixtures. The experimental data for the density ρ and speed of sound u for the [beim][triflate] (1) + water (2), [bmim][triflate] (1) + water (2), and [bmpyr][triflate] (1) + water (2) binary mixtures, as well as the isentropic compressibility κS and the molar isentropic compression KS,m, are given at several temperatures in Tables 3 to 5, respectively. As can be seen from these tables, the density always decreases when the temperature T increases and increases with the IL mole fraction, x1. The speed of sound of IL (1) + water (2) binary system at lower temperatures increases abruptly when x1 increases, starting from a value uo2 at x1 = 0, reaches a maximum value umax at x1 ≈ 0.05 to 0.10, and then slowly decreases until uo1 at x1 = 1. As temperature increases, uo2 (x1 = 0) increases, uo1 (x1 = 1) decreases, and the maximum falls at smaller x1 values. For the [beim][triflate] + water and [bmim][triflate] + water systems, the maximum has disappeared at T = 318.15 K, and u always decreases when x1 increases, a behavior similar to that observed for the 1958



Article

Table 5. Density ρ, Molar Volume Vm, Excess Molar Volume VmE, Speed of Sound u, Isentropic Compressibility κS, Molar Isentropic Compression KS,m, and Excess Molar Isentropic Compression KS,mE for the Binary System [bmpyr][triflate] (1) + Water (2) at T = (278.15 to 338.15) Ka ρ

106 Vm −3

−1

106 VmE

m ·mol

m ·mol

0.00000 0.04996 0.10003 0.15066 0.19995 0.29963 0.39861 0.49817 0.59961 0.69926 0.80169 0.89932 1.00000

999.99 1113.86 1163.55 1190.82 1208.34 1229.14 1240.96 1248.70 1254.27 1258.35 1261.86 1264.45 1267.23

18.016 28.433 38.980 49.709 60.137 81.283 102.308 123.466 145.023 166.198 187.919 208.638 229.895

0.000 −0.138 −0.202 −0.203 −0.219 −0.195 −0.145 −0.085 −0.025 0.033 0.050 0.079 0.000

0.00000 0.04996 0.10003 0.15066 0.19995 0.29963 0.39861 0.49817 0.59961 0.69926 0.80169 0.89932 1.00000

999.12 1108.53 1156.83 1183.59 1200.79 1221.49 1233.35 1241.17 1246.83 1251.01 1254.33 1256.90 1259.74

18.032 28.570 39.207 50.013 60.515 81.793 102.939 124.214 145.888 167.172 189.047 209.891 231.263

0.000 −0.088 −0.129 −0.122 −0.131 −0.110 −0.071 −0.028 0.012 0.045 0.077 0.099 0.000

0.00000 0.04996 0.10003 0.15066 0.19995 0.29963 0.39861 0.49817 0.59961 0.69926 0.80169 0.89932 1.00000

997.06 1102.75 1149.85 1176.19 1193.14 1213.77 1225.71 1233.63 1239.37 1243.63 1247.06 1249.64 1252.26

18.069 28.719 39.444 50.328 60.903 82.313 103.582 124.974 146.766 168.165 190.150 211.112 232.643

0.000 −0.045 −0.065 −0.049 −0.050 −0.031 −0.003 0.024 0.046 0.060 0.065 0.074 0.000

0.00000 0.04996 0.10003 0.15066 0.19995 0.29963 0.39861 0.49817 0.59961 0.69926 0.80169 0.89932 1.00000

994.05 1096.56 1142.62 1168.56 1185.37 1206.00 1218.04 1226.07 1231.92 1236.25 1239.76 1242.39 1245.09

18.124 28.882 39.694 50.656 61.302 82.843 104.234 125.745 147.653 169.168 191.269 212.344 233.983

0.000 −0.005 −0.001 0.029 0.035 0.058 0.081 0.099 0.107 0.109 0.098 0.095 0.000

3

κS

u

−1

kg·m

x1

3

m·s

−1

T = 278.15 K 1427.35 1595.92 1607.62 1602.88 1594.23 1574.07 1557.04 1543.69 1533.23 1525.34 1519.63 1513.98 1513.53 T = 288.15 K 1466.98 1594.66 1596.20 1586.00 1574.36 1551.59 1533.74 1519.95 1509.25 1501.05 1494.52 1488.86 1486.14 T = 298.15 K 1497.34 1590.37 1582.61 1567.82 1553.75 1528.95 1510.57 1496.58 1485.75 1477.53 1470.66 1465.01 1461.43 T = 308.15 K 1520.26 1583.04 1567.04 1548.46 1532.41 1506.16 1487.44 1473.42 1462.64 1454.45 1447.42 1441.96 1437.77

1959

TPa

1015 KS,m −1

−1

1015 KS,mE −1

m ·mol ·Pa 3


490.84 352.49 332.54 326.85 325.62 328.36 332.39 336.06 339.15 341.56 343.17 345.03 344.48

8.843 10.022 12.962 16.247 19.582 26.690 34.006 41.492 49.185 56.767 64.489 71.987 79.194

0.000 −2.771 −3.626 −4.067 −4.292 −4.254 −3.860 −3.277 −2.581 −1.848 −1.146 −0.328 0.000

465.09 354.75 339.28 335.89 335.99 340.06 344.68 348.75 352.10 354.77 356.93 358.91 359.42

8.386 10.135 13.302 16.799 20.332 27.815 35.481 43.319 51.368 59.308 67.477 75.333 83.120

0.000 −2.343 −3.141 −3.562 −3.785 −3.799 −3.494 −3.014 −2.432 −1.807 −1.142 −0.429 0.000

447.34 358.53 347.23 345.89 347.17 352.43 357.55 361.92 365.52 368.33 370.76 372.85 373.89

8.083 10.297 13.696 17.408 21.144 29.010 37.035 45.231 53.645 61.940 70.500 78.713 86.984

0.000 −2.020 −2.755 −3.148 −3.361 −3.397 −3.152 −2.744 −2.241 −1.700 −1.099 −0.463 0.000

435.27 363.90 356.40 356.90 359.25 365.52 371.07 375.69 379.44 382.38 385.01 387.11 388.53

7.890 10.510 14.147 18.079 22.023 30.281 38.678 47.241 56.025 64.686 73.640 82.201 90.908

0.000 −1.768 −2.441 −2.803 −3.002 −3.050 −2.845 −2.492 −2.052 −1.574 −1.021 −0.462 0.000



Article


106 Vm

106 VmE

u

κS

1015 KS,m

1015 KS,mE

x1

kg·m−3

m3·mol−1

m3·mol−1

m·s−1

TPa−1

m3·mol−1·Pa−1

m3·mol−1·Pa−1

0.00000 0.04996 0.10003 0.15066 0.19995 0.29963 0.39861 0.49817 0.59961 0.69926 0.80169 0.89932 1.00000

990.22 1089.97 1135.15 1160.74 1177.49 1198.16 1210.34 1218.51 1224.48 1228.90 1232.49 1235.16 1237.94

18.194 29.056 39.955 50.997 61.713 83.385 104.897 126.525 148.551 170.180 192.397 213.587 235.335

0.000 0.034 0.059 0.105 0.117 0.143 0.161 0.169 0.165 0.154 0.128 0.115 0.000

427.62 370.82 366.81 369.02 372.28 379.44 385.36 390.15 394.00 397.01 399.75 401.85 403.51

7.780 10.775 14.656 18.819 22.974 31.640 40.423 49.363 58.529 67.564 76.911 85.829 94.961

0.000 −1.565 −2.179 −2.509 −2.693 −2.744 −2.569 −2.261 −1.873 −1.449 −0.944 −0.450 0.000

0.00000 0.04996 0.10003 0.15066 0.19995 0.29963 0.39861 0.49817 0.59961 0.69926 0.80169 0.89932 1.00000

985.70 1083.01 1127.45 1152.76 1169.50 1190.27 1202.62 1210.95 1217.05 1221.57 1225.24 1227.97 1230.81

18.277 29.243 40.228 51.350 62.134 83.938 105.570 127.315 149.458 171.202 193.535 214.838 236.698

0.000 0.069 0.118 0.179 0.197 0.227 0.239 0.237 0.220 0.196 0.157 0.132 0.000

423.54 379.28 378.51 382.29 386.35 394.28 400.45 405.35 409.22 412.25 415.04 417.11 418.91

7.741 11.091 15.227 19.631 24.006 33.095 42.275 51.607 61.161 70.577 80.325 89.611 99.154

0.000 −1.397 −1.954 −2.247 −2.415 −2.461 −2.310 −2.037 −1.698 −1.325 −0.863 −0.424 0.000

0.00000 0.04996 0.10003 0.15066 0.19995 0.29963 0.39861 0.49817 0.59961 0.69926 0.80169 0.89932 1.00000

980.56 1075.72 1119.53 1144.53 1161.26 1182.30 1194.89 1203.39 1209.64 1214.26 1218.03 1220.81 1223.73

18.373 29.441 40.513 51.719 62.575 84.504 106.253 128.114 150.374 172.232 194.681 216.097 238.068

0.000 0.099 0.170 0.252 0.279 0.308 0.312 0.300 0.272 0.236 0.183 0.149 0.000

422.51 389.25 391.48 396.73 401.51 410.02 416.25 421.27 425.11 428.09 430.83 432.92 434.66

7.763 11.460 15.860 20.519 25.124 34.648 44.227 53.970 63.925 73.731 83.875 93.553 103.479

0.000 −1.257 −1.756 −2.006 −2.152 −2.190 −2.067 −1.814 −1.514 −1.185 −0.773 −0.368 0.000

T = 318.15 K 1536.76 1572.93 1549.72 1527.95 1510.38 1483.09 1464.25 1450.35 1439.72 1431.66 1424.66 1419.41 1414.89 T = 328.15 K 1547.68 1560.29 1530.79 1506.39 1487.68 1459.74 1441.00 1427.32 1416.99 1409.17 1402.31 1397.27 1392.66 T = 338.15 K 1553.61 1545.39 1510.53 1484.01 1464.50 1436.27 1417.95 1404.49 1394.51 1387.00 1380.44 1375.54 1371.14


[emim][triflate] + water system.12 Conversely, for the [bmpyr][triflate] + water system the maximum remains even at the highest temperature, T = 338.15 K. The anomalous behavior of the speed of sound of aqueous mixtures with x1 and T has repercussions on the isentropic compressibility κS, which has an opposite behavior to the speed of sound. It starts from a value κoS,2 at x1 = 0, reaches a minimum value κS,min at x1 ≈ 0.05 to 0.10, and then slowly increases until κoS,1 at x1 = 1. As temperature increases, κoS,2 (x1 = 0) decreases, and κoS,1 (x1 = 1) increases; the minimum drops at smaller x1 values. On the other hand, the molar isentropic compression always increases when x1 or T increases, and for this reason, we have preferred in the next section to calculate the excess molar isentropic

compression instead of the excess isentropic compressibility, since the KS,m behavior is more regular than that of κS. Excess Volumetric Properties of Liquid Mixtures. An excess thermodynamic property QE is defined as the difference between the actual value of the property, Q, and that corresponding for an ideal mixture at the same thermodynamic state, Qid: Q E = Q − Q id

(6)

where, in this case, Q can be Vm, κS, or KS,m. The ideal-mixture molar volume is defined as Vmid = x1·V1o + x 2·V 2o 1960

(7)



Article

where xi is the mole fraction of component i and V°i is the molar volume of pure component i at the mixture temperature and pressure. As far as the ideal isentropic compressibility κSid and the ideal molar isentropic compression KS,mid are concerned, Douhéret et al.25 stated they have to be calculated using the expressions of Benson and Kiyohara26 id

κS =

ϕ1κSo,1

+

ϕ2κSo,2

KS,m =

o x1KS,1

−

+

106 σ Zi,0

⎡ ϕ V o(α o )2 ϕ2V 2o(αpo,2)2 p ,1 1 1 + T⎢ + ⎢⎣ C po,1 C po,2

Vmid(αpid,m)2 ⎤ ⎥ − Cpid,m ⎥⎦ id

Table 6. Coefficients of the Fitting Equation for Excess Molar Volumes (106 VmE/m3·mol−1) and the Standard Deviations (σ) of the IL (1) + Water (2) Mixtures

(8)

o x 2KS,2

o 2 ⎡ x (E o )2 ) x 2(Ep,2 1 p,1 ⎢ +T + o o ⎢⎣ Cp,1 Cp,2

id 2 ⎤ (Ep,m ) ⎥ id Cp,m ⎥⎦

(9)

(10)

Epid,m = x1·Epo,1 + x 2·Epo,2

(11)

Cpid,m = x1·C po,1 + x 2·C po,2

(12)

Z Z Z Z

Z Z Z Z

0 1 2 3

Z Z Z Z

= = = =

A, A, A, A,

i i i i

= = = =

0 1 2 3

Z Z Z Z

= = = =

A, A, A, A,

i i i i

= = = =

0 1 2 3

[beim][triflate] (1) + Water (2) −0.6264 28.745 −5.3231 1.1441 −29.506 71.420 −0.6350 15.618 66.902 1.6124 −22.726 98.162 [bmim][triflate] (1) + Water (2) −0.57275 27.4480 −30.2626 0.48006 −20.0461 2.03473 −1.57308 26.9505 −65.8961 0.82470 −23.0940 64.0423 [bmpyr][triflate] (1) + Water (2) −0.44757 21.3940 59.4213 1.21621 −34.6267 124.7687 −0.55520 22.0792 −2.6037 1.41583 −28.0892 176.4514

0.0098

0.0068

0.0100

= = = =

A, i A, i A, i B, i

= = = =

0 1 2 1

= = = =

A, i A, i A, i B, i

= = = =

0 1 2 1

3

10 Zi,1

6

10 Zi,2

[beim][triflate] (1) + Water (2) −14.6779 159.850 −558.913 −1.3910 14.6396 1.9133 3.2865 −69.3308 508.908 0.88864 −2.0792 27.3681 [bmim][triflate] (1) + Water (2) −12.7522 137.435 −431.943 −1.7740 −17.4805 328.994 0.86435 0.025429 7.2437 [bmpyr][triflate] (1) + Water (2) −13.7461 114.254 −235.243 1.4261 −102.017 1038.47 6.2534 −166.303 1390.39 0.93847 −2.2373 20.4368


0.0376

0.0265

0.0291

in which N is the number of experimental data points, and m and n the degrees of polynomials in eq 13. The Akaike's Information Criterion29 was used to select the m and n values. The experimental values of VmE and KS,mE against the IL mole fraction x1 for each binary system as well as the curves obtained with the fitting parameters are shown in Figures 1 and 2, respectively. For the three IL + water systems studied, the excess molar volume VmE has a characteristic behavior. As seen in Figure 1, VmE is negative for low values of x1 and positive for high values of x1 at the lowest temperature. The higher temperature, the higher VmE, and the smaller the value of x1 in which VmE = 0. For temperatures higher than 318.15 K, VmE always remains positive, and it goes on increasing with temperature. The [emim][triflate] + water system11,12 and other IL + water systems present a similar behavior. The increase of VmE with the temperature for the systems reported in this work is a characteristic fact of all of the IL + water systems. In an exhaustive literature review in which 41 IL + water systems were consulted, only for one of them, the

n

(13)

in which all of the coefficients Zi (Z = A, B) for each system have been expressed as a second-order polynomial on T, (14)

In this way, the number of coefficients is strongly reduced.12 The least-squares method was used to estimate the parameters. In Tables 6 and 7, these parameter values are given, as well as the standard deviations calculated with the expression: ⎡ ∑ p (Q E − Q E )2 ⎤1/2 exptl, i calcd, i ⎥ i=1 σ=⎢ ⎢⎣ N − 3(m + n + 1) ⎥⎦

= = = =

Z = A, i = 0 Z = A, i = 1 Z = B, i = 1

m

Zi = Z i0 + Z i1(T − 273.15) + Z i2(T − 273.15)2

i i i i

Zi,0

∑i = 0 Ai (2x1 − 1)i 1 + ∑ j = 1 Bj (2x1 − 1) j

A, A, A, A,

m3·mol−1

10 Zi,2

1015 σ

The combined standard uncertainty for the ideal properties of a mixture is the same as that for the actual properties. In Tables 3 to 5, we have also reported excess molar volumes and excess molar isentropic compressions for the three binary systems. The excess properties, QE, for each system were correlated with the IL mole fraction using a modified27 Redlich−Kister28 equation Q E = x1(1 − x1)

= = = =

10 Zi,1

6

Table 7. Coefficients of the Fitting Equation for Excess Molar Isentropic Compression (1015 KS,mE/m3·mol−1·Pa−1) and the Standard Deviations (σ) of the IL (1) + Water (2) Mixtures

where ϕi (= xiVoi /Vmid) is the volume fraction of component i, whereas κoS,i, KoS,i, αop,i, Eop,i (= Vio·αop,i), and Cop,i are the isentropic compressibility, the molar isentropic compression, the isobaric thermal expansivity, the molar isobaric expansion, and the molar isobaric heat capacity, respectively, of pure component i at the mixture temperature and pressure. Furthermore, αp,mid, Ep,mid, and Cp,mid are the isobaric thermal expansivity, the molar isobaric expansion, and the molar isobaric heat capacity, respectively, of the ideal mixture which can be defined by25 αpid,m = ϕ1·αpo,1 + ϕ2 ·αpo,2

Z Z Z Z

3

(15) 1961



Article

Figure 1. Excess molar volume VmE for the IL (1) + water (2) binary systems at different temperatures: ●, 278.15 K; □, 288.15 K; ▲, 298.15 K; ○, 308.15 K; ■, 318.15 K; △, 328.15 K; ▼, 338.15 K. The solid lines represent the corresponding correlation by a modified Redlich−Kister equation (eq 13). IL: (a) [beim][triflate]; (b) [bmim][triflate]; (c) [bmpyr][triflate].

Figure 2. Excess molar isentropic compression KS,mE for the IL (1) + water (2) binary systems at different temperatures: ●, 278.15 K; □, 288.15 K; ▲, 298.15 K; ○, 308.15 K; ■, 318.15 K; △, 328.15 K; ▼, 338.15 K. The solid lines represent the corresponding correlation by a modified Redlich−Kister equation (eq 13). IL: (a) [beim][triflate]; (b) [bmim][triflate]; (c) [bmpyr][triflate].

pyrrolidinium octanoate + water system,30 the molar volume VmE has been reported to decrease when the temperature increases. The VmE data for the [bmim][triflate] + water system reported in the present work agree with those reported by Garcia-Miaja et al.13 within the experimental error. As it can be seen in Figure 2, the excess molar isentropic compression KS,mE for the IL + water system is negative for all of temperatures and compositions considered, and increases, that is, becomes less negative, with temperature. The fitting curves are symmetric enough and present a minimum at an IL mole fraction of x1 ≈ 0.20 to 0.30.

excess molar isentropic compressions KS,mE of mixtures have been obtained. The excess properties of each system were fitted to a modified Redlich−Kister equation, in which all of the parameters were expressed as a second-order polynomial on temperature. For all of the systems, the excess molar volume increases with temperature, this fact being a constant in the behavior of all of the IL + water systems. At lower temperatures, the excess molar volume goes from negative to positive values as the mole fraction of IL increases. At higher temperatures VmE remains always positive. On the other hand, KS,mE increases also when temperature increases, although it remains always negative.

■

CONCLUSIONS Experimental values of the density and the speed of sound of aqueous mixtures of [beim][triflate], [bmim][triflate], and [bmpyr][triflate] in the whole range of concentrations have been determined at T = (278.15 to 338.15) K and atmospheric pressure. From these quantities, excess molar volumes VmE and

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Fax: +34 963 544 898. 1962



Article

Funding

(18) Zech, O.; Stoppa, A.; Buchner, R.; Kunz, W. The conductivity of imidazolium-based ionic liquids from (238 to 468) K. B. Variation of anion. J. Chem. Eng. Data 2010, 55, 1774−1778. (19) Klomfar, J.; Souckova, M.; Patek, J. Temperature dependence measurements of the density at 0.1 MPa for 1-alkyl-3-methylimidazolium-based ionic liquids with the trifluoromethanesulfonate and tetrafluoroborate anion. J. Chem. Eng. Data 2010, 55, 4054−4057. (20) Gaciño, F. M.; Regueira, T.; Lugo, L.; Comuñas, M. J. P.; Fernández, J. Influence of molecular structure on densities and viscosities of several ionic liquids. J. Chem. Eng. Data 2011, 56, 4984− 4999. (21) Daubert, T. E.; Danner, R. P.; Sibul, H. M.; Stebbins, C. C. Physical and Thermodynamic Properties of Pure Chemicals: Data Compilation. DIPPR/AIChE; Taylor & Francis: Washington, DC, 1998. (22) Valderrama, J. O.; Toro, A.; Rojas, R. E. Prediction of the heat capacity of ionic liquids using the mass connectivity index and a group contribution method. J. Chem. Thermodyn. 2011, 43, 1068−1073. (23) Diedrichs, A.; Gmehling, J. Measurement of heat capacities of ionic liquids by differential scanning calorimetry. Fluid Phase Equilib. 2006, 244, 68−77. (24) Paulechka, Y. U.; Kabo, A. G.; Blokhin, A. V.; Kabo, G. J.; Shevelyova, M. P. Heat capacity of ionic liquids: Experimental determination and correlations with molar volume. J. Chem. Eng. Data 2010, 55, 2719−2724. (25) Douhéret, G.; Davis, M. I.; Reis, J. C. R.; Blandamer, M. J. Isentropic compressibilitiesExperimental origin and the quest for their rigorous estimation in thermodynamically ideal liquid mixtures. ChemPhysChem 2001, 2, 148−161. (26) Benson, G. C.; Kiyohara, O. Evaluation of excess isentropic compressibilities and isochoric heat capacities. J. Chem. Thermodyn. 1979, 11, 1061−1064. (27) Heintz, A.; Klasen, D.; Lehmann, J. K.; Wertz, C. Excess molar volumes and liquid−liquid equilibria of the ionic liquid 1-methyl-3octyl-imidazolium tetrafluoroborate mixed with butan-1-ol and pentan1-ol. J. Solution Chem. 2005, 34, 1135−1144. (28) Redlich, O.; Kister, A. T. Algebraic representation of thermodynamic properties and the classification of solutions. Ind. Eng. Chem. 1948, 40, 345−348. (29) Akaike, H. A new look at the statistical model identification. IEEE Trans. Automatic Control 1974, 19, 716−723. (30) Anouti, M.; Vigeant, A.; Jacquemin, J.; Brigouleix, C.; Lemordant, D. Volumetric properties, viscosity and refractive index of the protic ionic liquid, pyrrolidinium octanoate, in molecular solvents. J. Chem. Thermodyn. 2010, 42, 834−845.

This research was supported by the Ministerio de Ciencia e Innovación of the Spain Government and FEDER funds of the European Union, through Project No. CTQ2010-18848/PPQ. Notes

The authors declare no competing financial interest.

■

REFERENCES

(1) Brennecke, J. F.; Maginn, E. J. Ionic liquids: innovative fluids for chemical processing. AIChE J. 2001, 47, 2384−2389. (2) Heintz, A. Recent developments in thermodynamics and thermophysics of non-aqueous mixtures containing ionic liquids. A review. J. Chem. Thermodyn. 2005, 37, 525−535. (3) Huddleston, J. G.; Willauer, H. D.; Swatloski, R. P.; Visser, A. E.; Rogers, R. D. Room temperature ionic liquids as novel media for “clean” liquid-liquid extraction. Chem. Commun. 1998, 1765−1766. (4) Pereiro, A. B.; Araújo, J. M. M.; Esperança, J. M. S. S.; Marrucho, I. M.; Rebelo, L. P. N. Ionic liquids in separations of azeotropic systemsA review. J. Chem. Thermodyn. 2012, 46, 2−28. (5) Wasserscheid, P.; Keim, W. Ionic liquidsNew “solutions” for transition metals catalysis. Angew. Chem., Int. Ed. 2000, 39, 3772− 3789. (6) Dupont, J.; de Souza, R. F.; Suarez, P. A. Z. Ionic liquid (molten salt) phase organometallic catalysis. Chem. Rev. 2002, 102, 3667−3691. (7) Orchillés, A. V.; Miguel, P. J.; Vercher, E.; Martínez-Andreu, A. Isobaric vapor-liquid equilibria for 1-propanol + water + 1-ethyl-3methylimidazolium trifluoromethanesulfonate at 100 kPa. J. Chem. Eng. Data 2008, 53, 2426−2431. (8) Orchillés, A. V.; Miguel, P. J.; Vercher, E.; Martínez-Andreu, A. Using 1-ethyl-3-methylimidazolium trifluoromethanesulfonate as an entrainer for the extractive distillation of ethanol + water mixtures. J. Chem. Eng. Data 2010, 55, 1669−1674. (9) Orchillés, A. V.; Miguel, P. J.; González-Alfaro, V.; Vercher, E.; Martínez-Andreu, A. Isobaric vapor−liquid equilibria of 1-propanol + water + trifluoromethanesulfonate-based ionic liquid ternary systems at 100 kPa. J. Chem. Eng. Data 2011, 56, 4454−4460. (10) Huddleston, J. G.; Visser, A. E.; Reichert, W. M.; Willauer, H. D.; Broker, G. A.; Rogers, R. D. Characterization and comparison of hydrophilic and hydrophobic room temperature ionic liquids incorporating the imidazolium cation. Green Chem. 2001, 3, 156−164. (11) Rodríguez, H.; Brennecke, J. F. Temperature and composition dependence of the density and viscosity of binary mixtures of water + ionic liquid. J. Chem. Eng. Data 2006, 51, 2145−2155. (12) Vercher, E.; Orchillés, A. V.; Miguel, P. J.; Martínez-Andreu, A. Volumetric and ultrasonic studies of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid with methanol, ethanol, 1propanol, and water at several temperatures. J. Chem. Eng. Data 2007, 52, 1468−1482. (13) Garcia-Miaja, G.; Troncoso, J.; Romaní, L. Excess enthalpy, density, and heat capacity for binary systems of alkylimidazolium-based ionic liquids + water. J. Chem. Thermodyn. 2009, 41, 161−166. (14) Ge, M. L.; Zhao, R. S.; Yi, Y. F.; Zhang, Q.; Wang, L. S. Densities and viscosities of 1-butyl-3-methylimidazolium trifluoromethanesulfonate + H2O binary mixtures at T = (303.15 to 343.15) K. J. Chem. Eng. Data 2008, 53, 2408−2411. (15) Kell, G. S. Density, thermal expansivity, and compressibility of liquid water from 0° to 150 °C: correlations and tables for atmospheric pressure and saturation reviewed and expressed on 1968 temperature scale. J. Chem. Eng. Data 1975, 20, 97−105. (16) Vercher, E.; Llopis, F. J.; González-Alfaro, V.; Miguel, P. J.; Martínez-Andreu, A. Refractive indices and deviations in refractive indices of trifluoromethanesulfonate-based ionic liquids in water. J. Chem. Eng. Data 2011, 56, 4499−4504. (17) Jacquemin, J.; Ge, R.; Nancarrow, P.; Rooney, D. W.; CostaGomes, M. F.; Pádua, A. A. H.; Hardacre, C. Prediction of ionic liquid properties. I. Volumetric properties as a function of temperature at 0.1 MPa. J. Chem. Eng. Data 2008, 53, 716−726. 1963


Volumetric and Acoustic Properties of Aqueous Solutions of

Recommend Documents