Physicochemical Properties of Binary Mixtures of the Protic Ionic Liquid Bis(2-hydroxyethyl)methylammonium Formate with Methanol, Ethanol, and 1Propanol

J Solution Chem (2011) 40: 818–831DOI 10.1007/s10953-011-9680-8

Physicochemical Properties of Binary Mixturesof the Protic Ionic LiquidBis(2-hydroxyethyl)methylammonium Formatewith Methanol, Ethanol, and 1-Propanol

Kiki A. Kurnia · M.I. Abdul Mutalib · T. Murugesan ·B. Ariwahjoedi

Received: 18 August 2010 / Accepted: 16 October 2010 / Published online: 9 April 2011© Springer Science+Business Media, LLC 2011

Abstract Densities and viscosities were determined for binary mixtures containing the pro-tic ionic liquid bis(2-hydroxyethyl)methylammonium formate [BHEMF] with methanol,ethanol, and 1-propanol at four different temperatures (293.15, 303.15, 313.15, and323.15 K) and atmospheric pressure. Excess molar volume and viscosity deviations forthe binary system were calculated. The calculated results were fitted to a Redlich-Kisterequation to obtain the coefficients and estimate the standard deviations between the ex-perimental and calculated quantities. The negative values of excess volume molar for thesemixtures indicate that ion-dipole interactions and packing between ionic liquids and alcoholsare present. The values of viscosity deviation are also negative over the whole compositionrange, and their values become less negative as the temperature increases.

Keywords Protic ionic liquids · Density · Viscosity · Excess molar volumes · Viscositydeviation

1 Introduction

Ionic liquids are organic salts that are liquids at temperatures below 373.15 K [1]. Ionicliquids can be classified into two broad categories: aprotic ionic liquids and protic ionicliquids [2]. Protic ionic liquids are formed by simple proton transfer from a Brönsted acidto a Brönsted base. PILs are finding place in many chemical processes and electrochemicalapplication [2–13]. Hydroxyl ammonium ionic liquids are relatively new protic ionic liquidswith potential application in gas scrubbing. In previous studies, great attention has been paidto hydroxyl ammonium ionic liquids as solvents for SO2 and CO2 removal [13–16]. In our

K.A. Kurnia (�) · M.I.A. Mutalib · T. MurugesanDepartment of Chemical Engineering, Universiti Teknologi PETRONAS, Tronoh 31750, Malaysiae-mail: [email protected]

B. AriwahjoediDepartment of Fundamental and Applied Science, Universiti Teknologi PETRONAS, Tronoh 31750,Malaysia

J Solution Chem (2011) 40: 818–831 819

Fig. 1 Structure ofbis(2-hydroxyethyl)methylammoniumformate [BHEMF]

laboratory, hydroxyl ammonium ionic liquids have been mixed with an organic solvent toboost its absorption capacity for CO2. The main advantage of binary mixtures of hydroxylammonium ionic liquids with organic solvents is lower solution viscosity, which leads tolower energy requirements for absorption processes of CO2. In actual use, the physico-chemical properties of hydroxyl ammonium ionic liquids with organic solvent mixtures areextremely important. Especially, the density and viscosity data are significant from the prac-tical and theoretical viewpoint. Although applications of protic ionic liquids are well known,a detailed knowledge of the thermodynamic behavior of mixtures of protic ionic liquids withorganic solvents has not received a particularly large share of the literature on ionic liquidsstudies [17–28] and is still limited [29–31].

This paper is a continuation of a systematic program on the physicochemical propertiesof solutions containing hydroxyl ammonium ionic liquids. In the present work, the densityand viscosity of binary mixtures of the ionic liquid bis(2-hydroxyethyl)methylammoniumformate [BHEMF] with methanol, ethanol, and 1-propanol were determined over the wholeconcentration range at (293.15, 303.15, 313.15, and 323.15) K and atmospheric pressure.Meanwhile, the excess molar volume and viscosity deviation were calculated from the ex-perimental data.

2 Experimental

2.1 Materials

Bis(2-hydroxylethyl)methylammonium formate [BHEMF] was synthesized in our labora-tory according to standard methods developed and reported in the literature [32, 33]. Thestructure of [BHEMF] is shown in Fig. 1. The synthesized [BHEMF] was characterizedusing two techniques, 1H NMR and elemental analysis. 1H NMR spectra were measuredon a JEOL JNM-ECA400 spectrometer, using DMSO as solvent with TMS as the inter-nal standard. Elemental analyses were measured using a CHNS-932 (LECO Instruments)elemental analyzer. [BHEMF]: 1H-NMR (400 MHz, DMSO) δ = 8.35 ppm (s, 1H, HC–COO−), 6.63 ppm (broad, 4H, –NH and –OH), 3.64 ppm (t, 6H, –CH2–N), 2.91 ppm (t, 6H,–O–CH2), 2.56 ppm (m, 3H, H3C-N). Analysis % found (% calculated): C, 43.7 (43.6); H,9.1 (9.2); and N, 8.4 (8.5).

The water content was determined using a coulometric Karl Fischer titrator, DL 39 (Met-tler Toledo) using the Hydranal coulomat AG reagent (Riedel-de Haen). It was found that thewater content of [BHEMF] was 132 ppm. Methanol (high-performance liquid chromatog-raphy (HPLC) grade, w = 0.999), ethanol (analytical grade, w = 0.997), and 1-propanol(HPLC grade, w = 0.995) were purchased from Merck (Merck Sdn. Bhd., Malaysia). Allalcohols were dried with molecular sieves type 4 Å, (supplied by Aldrich). The impuritiesof these alcohols were determined by their water content and were found to be less than4 × 10−5 mass fraction. All chemicals were kept in bottles with PTFE septa, under vacuum,until further use.

820 J Solution Chem (2011) 40: 818–831

Table 1 Comparison of density (ρ) and viscosity (η) with literature values for the pure components atT = 298.15 K

Chemical ρ/g·cm−3 η/mPa·sThis work Lit. This work Lit.

[BHEMF] 1.17990 N/A 491.4 N/A

Methanol 0.7865 0.78664 [38] 0.5768 0.577 [38]

0.78664 [40] 0.543 [40]

Ethanol 0.7855 0.78517 [38] 1.0961 1.09 [38]

0.78522 [40] 1.085 [40]

0.7855 [39] 1.082 [39]

0.7890 [41] 1.0569 [41]

1-Propanol 0.7994 0.79952 [38] 1.9468 1.94 [38]

0.79940 [40] 1.951 [40]

0.7996 [39] 2.017 [39]

0.8036 [41] 2.1178 [41]

2.2 Apparatus and Procedures

Binary mixtures were prepared in glass vials with PTFE septa. Samples were taken fromthe vial with a syringe through the septum. The samples were prepared in an inert atmo-sphere glove box, using an analytical balance (Mettler Toledo, model AS120S, ±0.01 mg).The uncertainty of the composition on a mole fraction basis was 0.0001. The viscosity anddensity of the binary mixtures were measured simultaneously at temperatures from (293.15to 353.15) K using a rotational automated Anton Paar Stabinger Viscometer SVM3000.The reproducibility of the viscosity and density measurements are 0.35% and ±5 × 10−4

g·cm−3, respectively. The accuracy of the temperature measurement is ±0.02 K. The vis-cometer was calibrated using standard calibration fluid provided by the supplier followedby Millipore quality water and also some imidazolium ionic liquids with known viscosity[34–36]. All the measurements were done in triplicate and the average value is consideredfor further study, with the standard deviation of the measurements found to be lower than0.0004 g·cm−3. The experimental densities and viscosities of the pure chemicals comparedwith the available literature values are given in Table 1. From Table 1, it can be seen thatvalues for alcohols agree well with those reported in the literature. No previous data wasreported for [BHEMF] for comparison.

3 Results and Discussion

The experimental density and viscosity data for the binary systems [BHEMF](1) +methanol(2), or ethanol(2), or 1-propanol(2) at different T = (293.15,303.15,313.15, and323.15) K, and atmospheric pressure, are reported in Tables 2 and 3, respectively. Figures 2and 3 show the variation of density and viscosity, respectively, with the ionic liquid molarfraction, for the binary systems studied, at 293.15 K. The densities of the binary mixtureswere found to be lowest for the pure alcohol and to increase monotonically with increas-ing mole fraction of ionic liquid. The same trend was also observed for the viscosities ofthe binary mixtures. It is also observed from Tables 2 and 3 that both density and viscositydecrease with increasing temperature.

J Solution Chem (2011) 40: 818–831 821

Table 2 Experimental densities (ρ) of the binary mixtures [BHEMF](1) + alcohols(2)

x1 ρ/g·cm−3

293.15 K 303.15 K 313.15 K 323.15 K

{[BHEMF](1) + Methanol(2)}

0.0000 0.7912 0.7818 0.7723 0.7651

0.0524 0.8622 0.8533 0.8444 0.8374

0.1066 0.9187 0.9104 0.9020 0.8952

0.2075 0.9943 0.9866 0.9789 0.9720

0.3137 1.0477 1.0403 1.0331 1.0259

0.4061 1.0811 1.0740 1.0670 1.0596

0.5016 1.1077 1.1007 1.0939 1.0864

0.6339 1.1359 1.1292 1.1227 1.1150

0.7031 1.1479 1.1413 1.1348 1.1271

0.8195 1.1646 1.1581 1.1518 1.1439

0.9184 1.1759 1.1694 1.1630 1.1549

0.9620 1.1800 1.1734 1.1670 1.1587

1.0000 1.1833 1.1765 1.1699 1.1613

[BHEMF](1) + Ethanol(2)

0.0000 0.7893 0.7807 0.7725 0.7636

0.0643 0.8527 0.8444 0.8367 0.8281

0.1074 0.8881 0.8800 0.8725 0.8641

0.2133 0.9578 0.9500 0.9428 0.9346

0.3117 1.0071 0.9996 0.9925 0.9843

0.4170 1.0494 1.0420 1.0351 1.0268

0.5197 1.0832 1.0760 1.0691 1.0608

0.6178 1.1103 1.1032 1.0965 1.0881

0.7224 1.1346 1.1276 1.1209 1.1125

0.8275 1.1551 1.1482 1.1415 1.1330

0.9161 1.1701 1.1632 1.1566 1.1480

0.9500 1.1755 1.1687 1.1620 1.1534

1.0000 1.1833 1.1765 1.1699 1.1613

[BHEMF](1) + 1-Propanol(2)

0.0000 0.8032 0.7955 0.7876 0.7787

0.0561 0.8451 0.8376 0.8299 0.8213

0.1033 0.8767 0.8692 0.8617 0.8532

0.1976 0.9314 0.9241 0.9168 0.9084

0.3071 0.9845 0.9773 0.9702 0.9619

0.4049 1.0249 1.0178 1.0108 1.0025

0.5231 1.0669 1.0599 1.0530 1.0447

0.6246 1.0978 1.0909 1.0841 1.0757

0.7259 1.1246 1.1178 1.1110 1.1026

0.8079 1.1439 1.1370 1.1303 1.1218

0.9055 1.1646 1.1577 1.1511 1.1425

0.9558 1.1747 1.1678 1.1612 1.1526

1.0000 1.1833 1.1765 1.1699 1.1613

822 J Solution Chem (2011) 40: 818–831

Table 3 Experimental viscosities (η) of the binary mixtures [BHEMF](1) + alcohols(2)

x1 η/(mPa·s)

293.15 K 303.15 K 313.15 K 323.15 K

[BHEMF](1) + Methanol(2)

0.0000 0.6075 0.5535 0.5010 0.4601

0.0524 26.466 15.386 6.8225 4.6670

0.1066 52.082 24.582 13.122 8.9899

0.2075 103.06 49.041 26.157 17.870

0.3137 158.58 77.701 40.819 27.893

0.4061 207.61 101.96 54.121 37.051

0.5016 259.59 126.25 68.643 47.079

0.6339 339.04 163.03 91.649 62.818

0.7031 388.30 187.25 106.13 72.504

0.8195 494.56 243.28 136.36 92.044

0.9184 618.78 307.14 167.43 111.10

0.9620 667.17 330.26 179.61 118.90

1.0000 708.50 350.02 190.04 124.55

[BHEMF](1) + Ethanol(2)

0.0000 1.1802 1.0191 0.8424 0.7081

0.0643 32.410 17.439 8.4449 5.7993

0.1074 52.863 25.094 13.486 9.2541

0.2133 106.67 51.032 27.253 18.626

0.3117 159.33 78.197 41.191 28.123

0.4170 218.88 107.60 57.403 39.176

0.5197 281.64 137.16 74.929 51.059

0.6178 348.15 168.57 93.843 63.731

0.7224 434.62 211.69 118.33 79.693

0.8275 534.39 263.63 145.73 97.161

0.9161 630.30 312.26 169.99 112.21

0.9500 665.02 328.92 178.78 117.55

1.0000 708.50 350.02 190.04 124.55

[BHEMF](1) + 1-Propanol(2)

0.0000 2.1412 1.7880 1.3907 1.0977

0.0561 29.647 17.050 8.0824 5.5585

0.1033 51.953 25.073 13.550 9.3071

0.1976 99.807 47.756 25.737 17.595

0.3071 159.43 78.440 41.480 28.284

0.4049 216.75 106.85 57.049 38.830

0.5231 293.89 143.54 78.477 53.204

0.6246 369.52 179.84 99.709 67.209

0.7259 455.08 222.62 123.57 82.659

0.8079 531.24 261.84 144.29 95.858

0.9055 626.95 310.40 169.02 111.37

0.9558 671.35 331.94 180.42 118.72

1.0000 708.50 350.02 190.04 124.55

J Solution Chem (2011) 40: 818–831 823

Fig. 2 Density, ρ, of[BHEMF](1) + alcohol(2) binarymixtures at 293.15 K. Symbols:�, methanol; �, ethanol;�, 1-propanol

Fig. 3 Viscosity, η, of[BHEMF](1) + alcohol(2) binarymixtures at 293.15 K. Symbols:�, methanol; �, ethanol; �,1-propanol

The excess molar volume, V Em , and viscosity deviation, �η, were calculated by the fol-

lowing equations:

V Em =

N∑

i=1

xiMi(ρ−1 − ρ−1

i ) (1)

�η = η −N∑

i=1

xiηi (2)

where ρ and ρi are densities of the mixture and the density of pure components, respec-tively; Mi is the molar mass of the pure components; xi represents the mole fraction of thecomponent i; and η and ηi are the dynamic viscosity of the mixture and pure components,

824 J Solution Chem (2011) 40: 818–831

respectively. Values of the excess molar volume and viscosity deviation for [BHEMF](1) +methanol(2), or ethanol(2), or 1-propanol(2) are given in Tables 4 and 5, respectively.

The binary deviations at several temperatures were fitted to a Redlich-Kister [37] typeequation:

�Qij = xixj

N∑

p=0

Ap(xi − xj )p (3)

where �Qij is the excess property, xi and xj are the mole fractions of components i and j

respectively, Ap is the polynomial coefficient and N is the degree of the polynomial expan-sion, which was optimized using the F -test. These coefficients are summarized in Table 6,along with the corresponding standard deviations,

σ =√∑nDAT

Z (Zexp − Zcal)2

nDAT(4)

where nDAT is the number of experimental points, and Zexp and Zcal are experimental andcalculated data values, respectively.

The values of V Em as well as its Redlich-Kister fits are plotted in Figs. 4–6 for the con-

centration dependence of the excess molar deviation. The graphs of V Em indicate that all

mixtures of [BHEMF](1) + alcohol(2) exhibit negative deviations from ideality over theentire composition range. The negative excess molar volumes indicate that a tighter pack-ing and/or attractive interaction occurred when the ionic liquids and alcohol were mixed.The same behavior was also observed for binary mixtures of imidazolium ionic liquids andalcohols [38–40]. Graphs show also the unsymmetrical behavior of the changes in the ex-cess molar volumes with composition for these systems. The values of V E

m become morenegative in going from 1-propanol to methanol. The excess molar volume in these mixturesdecreases as the chain length of the alcohol decreases. It is known that in a series of alco-hols, the dielectric constants increase with decreasing carbon chain length. Therefore, thestrength of ion-dipole interactions between the [BHEMF] and the alcohols is in agreementwith the observed increasing order.

At higher temperatures, the minimum of V Em shifts to lower values for all three systems.

The high negative deviations from ideality, observed for these systems, was a result of strongintermolecular interactions between the ionic liquids and alcohols. In these binary mixtures,the observed V E

m values may be explained by four opposing contributions: (1) weakening ofthe interaction between the cation and the anion of ionic liquids during addition of alcohol;(2) contraction of the ionic liquids due to specific interactions with the alcohol; (3) sizedifference, and (4) expansion due to steric repulsion between the alkyl chain of an alcohol,i.e., 1-propanol, and that of [BHEMF], from van der Waals interactions between the alkanechains [38–40].

The values of �η, as well as its Redlich-Kister fits, are plotted in Figs. 7–9 for the con-centration dependence of the viscosity deviation. These graphs indicate that the viscositydeviations are negative over the whole composition range. The extent of the viscosity devi-ation is reduced as temperature increases and this behavior is similar for all systems. Theviscosity deviation is particularly significant in solutions with dilute alcohol content due tothe high differences in the viscosity of the two pure compounds. The viscosity deviation at293.15 K is greater than at 303.15 K or 318.15 K or 323.15 K due to the larger reduction inthe viscosity of the pure ionic liquid at higher temperature. The same type of behavior wasalso observed for the binary mixtures of imidazolium ionic liquids with alcohols [38–40].

J Solution Chem (2011) 40: 818–831 825

Table 4 Excess molar volume, V Em, of the binary mixtures [BHEMF](1) + alcohols(2)

x1 V Em/(cm3·mol−1)

293.15 K 303.15 K 313.15 K 323.15 K

[BHEMF](1) + Methanol(2)

0.0000 0.0000 0.0000 0.0000 0.0000

0.0524 −0.4379 −0.4718 −0.5093 −0.5473

0.1066 −0.7395 −0.7983 −0.8626 −0.9284

0.2075 −1.0511 −1.1338 −1.2237 −1.3161

0.3137 −1.1367 −1.2255 −1.3215 −1.4203

0.4061 −1.0924 −1.1793 −1.2730 −1.3696

0.5016 −0.9883 −1.0718 −1.1613 −1.2542

0.6339 −0.8078 −0.8878 −0.9729 −1.0623

0.7031 −0.7060 −0.7840 −0.8666 −0.9539

0.8195 −0.5086 −0.5773 −0.6495 −0.7266

0.9184 −0.2752 −0.3214 −0.3696 −0.4211

0.9620 −0.1371 −0.1662 −0.1960 −0.2278

1.0000 0.0000 0.0000 0.0000 0.0000

[BHEMF](1) + Ethanol(2)

0.0000 0.0000 0.0000 0.0000 0.0000

0.0643 −0.5744 −0.6114 −0.6580 −0.7142

0.1074 −0.8091 −0.8615 −0.9271 −1.0061

0.2133 −1.0618 −1.1314 −1.2176 −1.3204

0.3117 −1.0748 −1.1454 −1.2322 −1.3352

0.4170 −1.0020 −1.0672 −1.1471 −1.2417

0.5197 −0.9016 −0.9591 −1.0298 −1.1136

0.6178 −0.7798 −0.8286 −0.8887 −0.9602

0.7224 −0.6022 −0.6395 −0.6852 −0.7395

0.8275 −0.3661 −0.3891 −0.4167 −0.4489

0.9161 −0.1508 −0.1609 −0.1724 −0.1853

0.9500 −0.0786 −0.0842 −0.0903 −0.0969

1.0000 0.0000 0.0000 0.0000 0.0000

[BHEMF](1) + 1-Propanol(2)

0.0000 0.0000 0.0000 0.0000 0.0000

0.0561 −0.3673 −0.3920 −0.4257 −0.4685

0.1033 −0.5735 −0.6117 −0.6639 −0.7300

0.1976 −0.8002 −0.8526 −0.9239 −1.0139

0.3071 −0.8907 −0.9483 −1.0255 −1.1223

0.4049 −0.8972 −0.9552 −1.0314 −1.1259

0.5231 −0.8466 −0.9015 −0.9722 −1.0587

0.6246 −0.7446 −0.7931 −0.8547 −0.9293

0.7259 −0.5760 −0.6133 −0.6604 −0.7174

0.8079 −0.3947 −0.4197 −0.4515 −0.4902

0.9055 −0.1633 −0.1729 −0.1856 −0.2012

0.9558 −0.0643 −0.0679 −0.0728 −0.0789

1.0000 0.0000 0.0000 0.0000 0.0000

826 J Solution Chem (2011) 40: 818–831

Table 5 Viscosity deviation, �η, of the binary mixtures [BHEMF] (1) + alcohols (2)

x1 �η/mPa·s293.15 K 303.15 K 313.15 K 323.15 K

[BHEMF](1) + Methanol(2)

0.0000 0 0 0 0

0.0524 −11.2066 −3.4660 −3.6027 −2.2906

0.1066 −23.9721 −13.2173 −7.5797 −4.6958

0.2075 −44.4456 −24.0338 −13.6772 −8.3417

0.3137 −64.0702 −32.4696 −19.1349 −11.4906

0.4061 −80.4898 −40.5170 −23.3557 −13.8054

0.5016 −96.0906 −49.5897 −26.9299 −15.6248

0.6339 −110.3212 −59.0640 −29.0068 −16.3082

0.7031 −110.0375 −59.0184 −27.6443 −15.2082

0.8195 −86.1857 −43.6696 −19.4769 −10.1128

0.9184 −31.9715 −14.3692 −7.1453 −3.3272

0.9620 −14.3966 −6.4704 −3.2175 −0.9347

1.0000 0 0 0 0

[BHEMF](1) + Ethanol(2)

0.0000 0 0 0 0

0.0643 −14.2693 −6.0301 −4.5677 −2.8752

0.1074 −24.2849 −13.4087 −7.6768 −4.7551

0.2133 −45.4070 −24.4396 −13.9510 −8.5020

0.3117 −62.3261 −31.6062 −18.6248 −11.1878

0.4170 −77.2580 −38.9577 −22.3362 −13.1764

0.5197 −87.1145 −45.2281 −24.2337 −14.0068

0.6178 −90.0234 −48.0622 −23.8878 −13.4892

0.7224 −77.5446 −41.4554 −19.1946 −10.4838

0.8275 −52.0812 −26.1814 −11.6713 −6.0248

0.9161 −18.8279 −8.4661 −4.1683 −1.9479

0.9500 −8.1021 −3.6432 −1.7937 −0.8050

1.0000 0 0 0 0

[BHEMF](1) + 1-Propanol(2)

0.0000 0 0 0 0

0.0561 −12.1270 −4.2761 −3.8931 −2.4660

0.1033 −23.1685 −12.6947 −7.3321 −4.5458

0.1976 −41.8897 −22.8328 −12.9255 −7.8939

0.3071 −59.6329 −30.2892 −17.8441 −10.7267

0.4049 −71.3731 −35.9216 −20.7189 −12.2496

0.5231 −77.7532 −40.4141 −21.5982 −12.4743

0.6246 −73.8058 −39.4538 −19.5102 −10.9972

0.7259 −59.7826 −31.9346 −14.7574 −8.0494

0.8079 −41.5456 −21.2726 −9.5043 −4.9740

0.9055 −14.7787 −6.7015 −3.1876 −1.5133

0.9558 −5.9115 −2.6806 −1.2750 −0.3751

1.0000 0 0 0 0

J Solution Chem (2011) 40: 818–831 827

Table 6 Fitting parameters, Ap , of the Redlich-Kister equation, Eq. 3 with standard deviation, σ (Eq. 4) forbinary mixtures at T = (293.15,303.15,313.15, and 323.15) K

T/K A0 A1 A2 A3 A4 σ

[BHEMF](1) + Methanol(2)V E

m/cm3·mol−1 293.15 −3.9649 2.4595 −2.6302 0.3557 −0.2665 0.003303.15 −4.3006 2.5409 −2.9834 0.2593 −0.3851 0.002313.15 −4.6604 2.6358 −3.3618 0.1765 −0.5082 0.002323.15 −5.0335 2.7213 −3.7715 0.0811 −0.6202 0.002

�η/mPa·s 293.15 −381.0 −338.3 −266.9 282.4 444.3 1.78303.15 −196.0 −193.9 −188.8 194.1 336.9 0.94313.15 −107.5 −66.9 −30.0 74.0 80.5 0.22323.15 −62.3 −32.7 −12.8 48.7 50.7 0.09

[BHEMF](1) + Ethanol(2)V E

m/cm3·mol−1 293.15 −3.6901 2.0837 −2.5966 3.1174 −0.0086 0.002303.15 −3.9265 2.2418 −2.7682 3.2805 −0.0125 0.001313.15 −4.2169 2.4318 −2.9810 3.5113 −0.0187 0.002323.15 −4.5611 2.6523 −3.2379 3.8129 −0.0243 0.002

�η/mPa·s 293.15 −342.7 −169.6 −25.8 239.3 238.2 1.72303.15 −176.7 −102.0 −44.4 159.5 184.9 0.62313.15 −96.4 −24.0 20.5 56.2 33.7 0.12323.15 −56.0 −7.8 16.6 31.9 15.4 0.07

[BHEMF](1) + 1-Propanol(2)V E

m/cm3·mol−1 293.15 −3.4480 1.1969 −0.9442 2.3074 −0.1197 0.001303.15 −3.6715 1.2690 −1.0036 2.4865 −0.1317 0.002313.15 −3.9603 1.3878 −1.1069 2.7060 −0.1463 0.003323.15 −4.3143 1.5525 −1.2542 2.9674 −0.1612 0.002

�η/mPa·s 293.15 −308.9 −56.6 82.2 143.9 94.2 1.75303.15 −158.6 −39.4 7.9 98.5 114.5 0.92313.15 −86.8 3.9 38.7 30.6 6.4 0.28323.15 −50.3 7.2 23.3 17.9 4.3 0.06

Fig. 4 Excess molar volumes,Eq. 3, for the system[BHEMF](1) + methanol(2) as afunction of mole fraction, x1, atseveral temperatures. Symbols:�, T = 293.15 K; �,T = 303.15 K; �, T = 313.15 K;�, T = 323.15 K. The dashedlines were calculated using Eq. 3

828 J Solution Chem (2011) 40: 818–831

Fig. 5 Excess molar volumes,V E

m, for the system [BHEMF](1)+ ethanol(2) as a function ofmole fraction, x1, at severaltemperatures. Symbols: �,T = 293.15 K; �, T = 303.15 K;�, T = 313.15 K; �,T = 323.15 K. The dashed lineswere calculated using Eq. 3

Fig. 6 Excess molarvolumes,V E

m , for the system[BHEMF](1) + 1-propanol(2) asa function of mole fraction, x1, atseveral temperatures. Symbols:�, T = 293.15 K; �,T = 303.15 K; �, T = 313.15 K;�, T = 323.15 K. The dashedlines were calculated using Eq. 3

Fig. 7 Viscosity deviation, �η,for the system [BHEMF](1) +methanol(2) as a function ofmole fraction, x1, at severaltemperatures. Symbols: �,T = 293.15 K; �, T = 303.15 K;�, T = 313.15 K; �,T = 323.15 K. The dashed lineswere calculated using Eq. 3

J Solution Chem (2011) 40: 818–831 829

Fig. 8 Viscosity deviation, �η,for the system [BHEMF](1) +ethanol(2) as a function of molefraction, x1, at severaltemperatures. Symbols: �,T = 293.15 K; �, T = 303.15 K;�, T = 313.15 K; �,T = 323.15 K. The dashed lineswere calculated using Eq. 3

Fig. 9 Viscosity deviation, �η,for the system [BHEMF](1) +1-propanol(2) as a function ofmole fraction, x1, at severaltemperatures. Symbols: �,T = 293.15 K; �, T = 303.15 K;�, T = 313.15 K; �,T = 323.15 K. The dashed lineswere calculated using Eq. 3

4 Conclusions

This paper reports experimental data for the densities and viscosities of the binary systemsof bis(2-hydroxyethyl)methylammonium formate [BHEMF] with methanol, ethanol, and 1-propanol at (293.15, 303.15, 313.15, and 323.15) K. The densities and viscosities increasewith increasing mole fraction of the ionic liquid and decrease with increasing temperature.Excess molar volumes, V E

m , and viscosity deviations, �η, of these binary mixtures were cal-culated from experimental density and viscosity data. The negative excess molar volumesfor these mixtures indicate that ion–dipole interactions and packing between ionic liquidsand alcohols are present. The excess molar volume in these mixtures decreases as the chainlength of alcohol decreases. At higher temperatures, the minimum of the excess molar vol-ume shifts to the lower values for all three systems. The �η values are also negative over thewhole composition range. The extent of the viscosity deviation decreases as the temperatureincreases and this behavior is similar for all systems.

830 J Solution Chem (2011) 40: 818–831

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