Achievement of a Homogeneous Phase in Ternary Ionic Liquid

Mar 3, 2010 - Maritime and Materials Engineering, Delft UniVersity of Technology, ... system consisting of 1-hexyl-3-methylimidazolium tetrafluo- robo...
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Ind. Eng. Chem. Res. 2010, 49, 3474–3478

Achievement of a Homogeneous Phase in Ternary Ionic Liquid/Carbon Dioxide/ Organic Systems Maaike C. Kroon,† Louw J. Florusse,† Eliane Ku¨hne,† Geert-Jan Witkamp,† and Cor J. Peters*,†,‡ Section Process Equipment Department of Process & Energy Faculty of Mechanical, Maritime and Materials Engineering, Delft UniVersity of Technology, Leeghwaterstraat 44, 2628 CA Delft, Netherlands, and The Petroleum Institute, Chemical Engineering Department, P.O. Box 2533, Abu Dhabi, U.A.E.

A few years ago, it was found that carbon dioxide (CO2) is able to induce in ternary ionic liquid (IL) + organic systems, a “two-phase (L + V)-three-phase (L1 + L2 + V)-two-phase (L1 + L2)” transition by pressure increase. In the two liquid phase region (L1 + L2), one of the phases did not contain any IL. Therefore, the organic compound could be separated from the IL at increased CO2 pressure without any IL contamination. However, the occurrence of a homogeneous phase by further pressure increase, a so-called L1 + L2 f L transition, in the same systems was never observed before. Here, we demonstrate that in addition a third phase transition is possible upon further CO2 pressure increase, where the two liquid phases (L1 + L2) can be forced to form one homogeneous liquid phase (L). This phenomenon has promising implications for reactions and separations in systems using ILs. As an example, we present the phase behavior of the ternary system consisting of 1-hexyl-3-methylimidazolium tetrafluoroborate ([hmim+][BF4-]) + CO2 + 2-propanol, which was measured using the Cailletet apparatus. This equipment allows measurements of phase equilibria with high accuracy: the uncertainties in temperature, pressure, and mole fraction are 0.02 K, 0.0025 MPa, and 0.005 (-), respectively.6 Results are presented in Table 1 and graphically depicted in Figure 1. Figure 1 shows the phase diagram of the ternary [hmim+][BF4-]) + CO2 + 2-propanol system at CO2 mole fractions ranging from 10.01 to 60.23 mol %, while the mixing ratio of 2-propanol:[hmim+][BF4-] is kept constant at 20:1. At low CO2 mole fractions (until 30.03 mol %), a two-phase L + V region and a one-phase region L are present. As the CO2 mole fraction increases (between 39.97 mol % and 55.18 mol %), two two-phase regions L1 + L2 and two three-phase regions L1 + L2 + V appear at low and high temperature. Further CO2 mole fraction increase results in the two two-phase L1 + L2 regions to approach each other, narrowing the temperature window for occurrence of a homogeneous one-phase region L. At a fraction of 55.96 mol %, the homogeneous phase is completely surrounded by the two-phase L1 + L2 region. The homogeneous phase shifts rapidly to higher pressures upon further increase of the CO2 mole fraction. A closer look at the phase diagram at a CO2 fraction of 55.96 mol % in Figure 1 shows that one can encounter three different phase transitions upon increasing pressure: (i) L + V f L1 + L2 + V, (ii) L1 + L2 + V f L1 + L2, and (iii) L1 + L2 f L. This miscibility behavior with increasing pressure is schematically shown in Figure 2. The first two transitions have been noticed before and were then called lower critical end point * To whom correspondence should be addressed. Tel.: +31-152782660. Fax: +31-15-2786975. E-mail: [email protected]; [email protected]. † Delft University of Technology. ‡ The Petroleum Institute.

(LCEP) and K-point.1-5 The third transition from a biphasic into a homogeneous liquid phase was overlooked in these earlier studies.1-5 Although this phase behavior was found earlier for ternary CO2 + organic systems,7-9 this is the first time that the occurrence of a L1 + L2 f L transition was observed in a ternary system with an IL involved. It should be noticed that the L1 + L2 f L transition can only be found in a small range of CO2 mole fractions (around 55.96 mol %). At lower or higher concentrations, the L1 + L2 f L transition is absent. Earlier research on ternary IL + CO2 + organic systems only found the existence of a homogeneous phase of the nature L + V f L, as seen at the lower CO2 mole fractions.10 At higher CO2 concentrations, the homogeneous phase of the nature L1 + L2 f L shifts to very high pressures, leaving this phase transition undiscovered in previous studies. Another major observation is that none of the three phase transitions involve criticality. This means that the previously used nomenclature for the L + V f L1 + L2 + V transition (LCEP) and for the L1 + L2 + V f L1 + L2 transition (Kpoint) is incorrect.11 The proof of noncriticality simply follows from the Gibbs phase rule: F)2+N-π-R

(1)

where F is the number of degrees of freedom, N is the number of components, π is the number of phases present at equilibrium, and R represents the extra restrictions on the system. As pointed out elsewhere,12,13 there are two additional restrictions (R ) 2) in the case of criticality. If the first two phase transitions were critical, then the number of degrees of freedom would be one (F ) 2 + 3 2 - 2 ) 1). However, the measured phase transitions have two degrees of freedom i.e., one has to choose two variables (e.g., composition and temperature) to fix the third variable

10.1021/ie901405p  2010 American Chemical Society Published on Web 03/03/2010

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Figure 1. Phase behavior of the ternary [hmim+][BF4-] + CO2 + 2-propanol (ratio 2-propanol:[hmim+][BF4-] ) 20:1).

Figure 2. Schematic of [hmim+][BF4-] + CO2 + 2-propanol phase behavior at a CO2 concentration of 55.96 mol %.

(e.g., pressure). Therefore, the L + V f L1 + L2 + V transition and the L1 + L2 + V f L1 + L2 transition measured in this work cannot be critical end points, i.e., the previously used nomenclature is thus incorrect. This does not mean that ternary ionic liquid + CO2 + organic systems cannot show lower critical end point lines and/or tricritical points at other ionic liquid:methanol ratios. If the newly discovered phase transition (L1 + L2 f L) were a critical end point, then the number of degrees of freedom would be two (F ) 2 + 3 -1 - 2 ) 2). However, the measured phase transition has three degrees of freedom. Only choosing two variables (e.g., composition and pressure) is not enough to fix the third variable (e.g., temperature).

Instead, as can be seen from the phase diagram at a CO2 fraction of 55.96%, even if composition and pressure have been chosen, there are still two temperatures possible. Therefore, the L1 + L2 f L transition cannot be critical either. The newly discovered L1 + L2 f L transition gives rise to a new way of chemical processing, where the CO2 is not only used as a transporting agent for reactants and products in the reaction step and/or as extracting agent for removal of the organic from the IL phase in the separation step.14-16 Instead, CO2 could also be used in a reaction step to enhance the formation of a homogeneous phase. In this homogeneous liquid phase L, the reactions can be carried out at high rates without any mass transfer limitations. Subsequently, the product can still be recovered in the two liquid phase region L1 + L2 from the liquid phase that does not contain any IL. The transition between the homogeneous region and the biphasic region can simply be achieved by a small change in pressure. Finally, the results show that the phase behavior of IL + CO2 + organic mixtures is complex. If one would like to carry out a reaction in an IL + CO2 system, then one can expect the formation of additional phases and/or merging of different phases during reaction. This is the result of changing phase behavior with changing concentration of the organic during reaction.

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Table 1. Phase Behavior of the Ternary [hmim+][BF4-] + CO2 + 2-Propanol Systema xCO2/-

T/K

P/MPa

equilibrium

T/K

P/MPa

0.1001

253.56 258.49 263.51 268.58 273.49 278.57 283.50 284.94 288.50 253.73 258.58 263.48 268.48 273.55 278.56 283.55 288.80 253.52 258.54 263.49 268.49 273.49 278.56 283.54 288.54 253.59 258.56 263.60 268.48 273.46 274.33 274.45 273.15 273.68 274.25 274.48 274.70 253.66 258.48 263.50 268.44 272.74 273.41 274.36 275.20 275.46 275.89 272.73 273.49 274.35 253.35 258.47 263.55 268.49 273.42 275.90 277.48 278.07 278.56 279.07 279.48 280.36 281.08 281.69 277.52 278.07 278.37 279.07 279.48 280.37 281.07 281.74 275.89 276.00

0.562 0.632 0.707 0.787 0.872 0.957 1.047 1.072 1.137 1.052 1.187 1.327 1.482 1.647 1.812 1.992 2.172 1.442 1.637 1.842 2.062 2.297 2.542 2.802 3.072 1.702 1.932 2.197 2.467 2.757 2.812 2.817 9.102 6.747 4.347 3.447 2.713 1.822 2.062 2.342 2.657 2.907 2.967 3.032 3.087 3.102 3.137 12.652 9.927 7.527 1.816 2.091 2.381 2.691 3.021 3.201 3.311 3.366 3.396 3.441 3.461 3.531 3.586 3.631 10.396 9.326 8.981 7.676 7.061 5.776 4.856 4.201 2.922 2.951

L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 LV f L L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 LV f L LV f L L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 LV f L LV f L LV f L L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2 f L L1L2 f L L1L2 f L L1L2 f L LV f L1L2V L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2 f L L1L2 f L L1L2 f L L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L LV f L1L2V LV f L1L2V

293.44 298.64 303.47 308.43 313.38 318.55 323.40 328.50

1.232 1.332 1.427 1.522 1.627 1.732 1.832 1.932

LV LV LV LV LV LV LV LV

293.53 298.46 303.49 308.46 313.65 318.44 323.47 328.47 293.49 298.50 303.49 308.46 313.50 318.50 323.45 328.48 275.17 276.53 277.24 278.49 279.26 278.57 283.58 288.49 293.64 298.43 303.58 308.50 275.23 275.45 275.97 275.22 275.46 275.95 277.05 278.48 283.54 288.51 293.47 298.43 303.50 277.48 278.07 278.54 279.07 279.48 280.36 281.07 281.72 282.25 283.46 288.48 293.53 298.46 303.44 308.44 313.59 318.49 323.45 328.58 333.60 338.57 343.61 348.75

2.362 2.552 2.747 2.942 3.147 3.342 3.537 3.732 3.347 3.637 3.927 4.222 4.522 4.817 5.107 5.402 2.583 2.340 2.203 1.986 1.788 3.082 3.412 3.752 4.122 4.472 4.867 5.247 5.252 4.777 3.597 3.003 3.023 3.077 3.217 3.317 3.702 4.067 4.467 4.882 5.322 3.196 3.256 3.306 3.356 3.401 3.491 3.556 3.571 3.681 3.771 4.176 4.606 5.036 5.491 5.956 6.446 6.921 7.401 7.891 8.371 8.841 9.301 9.756

LV f L LV f L LV f L LV f L LV f L LV f L LV f L LV f L LV f L LV f L LV f L LV f L LV f L LV f L LV f L LV f L LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L LV f L LV f L LV f L LV f L LV f L LV f L L1L2 f L L1L2 f L L1L2 f L LV f L1L2V LV f L1L2V LV f L1L2V LV f L LV f L LV f L LV f L LV f L LV f L LV f L LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L LV f L LV f L LV f L LV f L LV f L LV f L LV f L LV f L LV f L LV f L LV f L LV f L LV f L LV f L

0.2004

0.3003

0.3997

0.4508

0.5005

equilibrium f f f f f f f f

L L L L L L L L

T/K

P/MPa

equilibrium

333.51 338.69 343.54 348.73 353.74 358.57 363.63 368.64

2.037 2.137 2.237 2.337 2.437 2.532 2.632 2.732

LV LV LV LV LV LV LV LV

f f f f f f f f

L L L L L L L L

333.55 338.59 343.53 348.43 353.68 358.59 363.65 368.62 333.48 338.67 343.42 348.50 353.53 358.70 363.65 368.59 313.55 318.45 323.47 328.48 333.58 338.48 343.55 348.49 353.66 358.46 363.65 368.65 308.45 313.45 318.44 323.39 328.51 333.48 338.48 343.51 348.55 353.39 358.73 363.65

3.932 4.127 4.317 4.487 4.672 4.862 5.032 5.197 5.692 5.987 6.262 6.532 6.792 7.067 7.312 7.552 5.647 6.027 6.422 6.817 7.207 7.577 7.952 8.312 8.677 9.007 9.347 9.672 5.747 6.197 6.662 7.107 7.562 8.012 8.467 8.947 9.322 9.717 10.147 10.537

LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV

f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f

L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L

353.68 358.58 359.54 360.28 361.08 361.97 363.69 365.11 366.55 368.19 370.10 361.08 361.98 363.69 365.10 366.55 361.08 361.98 363.69 365.10 366.56 368.19 370.10

10.186 10.591 10.666 10.726 10.781 10.846 10.951 11.056 11.151 11.256 11.381 10.836 11.046 11.571 11.936 12.366 10.771 10.821 10.911 10.986 11.061 11.136 11.216

LV f L LV f L LV f L LV f L L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L LV f L1L2V LV f L1L2V LV f L1L2 V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V

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Table 1. Continued xCO2/-

T/K

P/MPa

equilibrium

T/K

P/MPa

0.5209

253.66 258.55 263.50 268.45 273.48 278.47 279.76 281.01 282.17 283.53 285.15 286.00 278.51 279.75 281.00 282.17 283.45 285.16 278.47 279.76 281.01 253.48 258.57 263.49 268.42 273.44 278.44 281.12 283.44 284.77 286.00 287.31 288.45 289.78 291.08 291.77 293.48 295.95 298.43 283.43 284.82 285.96 287.31 289.80 291.07 291.77 293.48 295.95 298.42 253.45 258.56 263.40 268.55 273.53 274.85 275.52 276.18 278.45 279.91 281.12 283.46 285.99 288.52 290.95 293.46 295.97 298.43 299.02 283.46 286.03 288.51 290.95 293.49 295.96

1.859 2.119 2.414 2.729 3.074 3.439 3.539 3.644 3.729 3.844 3.979 4.059 12.609 10.784 9.119 7.774 6.474 5.019 3.315 3.449 3.559 1.861 2.136 2.431 2.751 3.101 3.476 3.696 3.891 3.991 4.091 4.206 4.306 4.431 4.541 4.606 4.756 4.986 5.231 12.146 10.971 9.986 9.046 7.696 7.096 6.816 6.241 5.686 5.321 1.856 2.141 2.426 2.756 3.111 3.201 3.256 3.306 3.481 3.576 3.691 3.886 4.116 4.311 4.531 4.766 5.016 5.226 5.291 12.236 10.086 8.446 7.231 6.331 5.766

L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L LV f L1L2V LV f L1L2V LV f L1L2V L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L

282.17 283.53 285.16 286.00 286.52 288.53 293.50 298.48 303.46 308.42 313.46 318.42 323.46 328.44 333.54 338.56 342.78 343.57 346.08 348.56 350.97 278.51 281.09 283.49 284.78 285.98 287.32 288.47 289.78 291.07 291.77 293.48 295.95 298.42 299.48 303.42 308.43 313.51 318.41 322.03 323.44 326.01 328.51 330.96 333.52 335.99 338.54 341.05 343.51 276.18 278.55 279.93 281.00 283.46 285.99 288.51 290.93 293.47 295.97 298.45 299.02 303.50 308.57 313.58 318.41 322.03 323.57 325.94 328.52 331.03 333.53 336.06 338.49 341.03

3.664 3.804 3.954 4.039 4.094 4.264 4.699 5.159 5.624 6.114 6.614 7.114 7.624 8.129 8.649 9.129 9.539 9.614 9.829 10.039 10.249 3.331 3.586 3.801 3.926 4.041 4.171 4.276 4.391 4.521 4.581 4.741 4.971 5.221 5.331 5.716 6.216 6.736 7.246 7.621 7.766 8.031 8.291 8.541 8.796 9.041 9.281 9.526 9.756 3.072 3.336 3.476 3.621 3.806 4.051 4.276 4.501 4.741 4.991 5.201 5.281 5.726 6.231 6.756 7.246 7.646 7.781 8.031 8.301 8.546 8.801 9.056 9.281 9.541

0.5410

0.5518

equilibrium LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f L1L2V L1L2V L1L2V L1L2V L1L2V LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f LV f L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V

L1L2V L1L2V L1L2V L1L2V L L L L L L L L L L L L f L1L2 f L1L2 f L1L2 f L1L2 f L1L2 L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L L L L L f L1L2 f L1L2 f L1L2 f L1L2 f L1L2 f L1L2 f L1L2 f L1L2 f L1L2 f L1L2 L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L L L L f L1L2 f L1L2 f L1L2 f L1L2 f L1L2 f L1L2 f L1L2 f L1L2 f L1L2

T/K

P/MPa

equilibrium

352.38 356.06 358.56 363.62 368.70 342.78 343.52 346.06 348.55 350.98 352.37 342.78 343.54 346.07 348.56 350.98 352.38 356.05 358.56 363.59 368.67 348.57 353.61 358.59 363.69 368.69 323.44 325.99 328.49 330.94 333.52 335.98 338.56 322.03 323.44 326.01 328.50 330.94 333.52 335.98 338.54 341.05 343.51 348.55 353.61 358.57 363.68 368.67

10.364 10.669 10.884 11.244 11.589 9.599 9.784 10.499 11.209 11.844 12.299 9.519 9.594 9.799 9.984 10.159 10.259 10.494 10.659 10.940 11.185 10.216 10.651 11.071 11.466 11.841 7.991 8.591 9.341 9.921 10.621 11.246 11.926 7.611 7.756 8.011 8.251 8.486 8.731 8.951 9.186 9.411 9.606 10.001 10.341 10.681 10.966 11.206

L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V

353.56 358.57 363.67 368.67 322.01 323.51 325.95 328.51 331.00 333.56 336.05 338.50 322.02 323.54 325.94 328.51 331.03 333.54 336.06 338.49 341.02 343.50 348.57 353.52 358.61

10.656 11.081 11.456 11.826 7.771 8.086 8.686 9.281 9.921 10.571 11.221 11.916 7.626 7.771 8.006 8.256 8.496 8.736 8.966 9.171 9.396 9.611 10.006 10.356 10.681

L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V

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Table 1. Continued xCO2/-

0.5596

0.6023

a

T/K

P/MPa

equilibrium

T/K

P/MPa

equilibrium

T/K

P/MPa

equilibrium

298.46 299.02 275.52 253.48 258.51 263.47 268.45 273.48 278.53 283.47 288.56 290.98 293.52 295.97 298.43 303.47 308.44 313.47 318.42 323.51 325.93 328.46 333.47 281.48 281.54 287.64 289.26 292.79 295.22 297.14 299.16 300.94 304.83 310.52 313.42 314.20 315.46 317.37 317.99 319.76 322.04

5.481 5.336 2.987 1.866 2.141 2.441 2.766 3.116 3.501 3.896 4.351 4.546 4.791 5.006 5.246 5.746 6.251 6.766 7.291 7.811 8.061 8.336 8.841 3.850 3.855 4.380 4.525 4.870 5.095 5.295 5.465 5.655 6.045 6.645 6.970 7.030 7.185 7.395 7.455 7.635 7.890

L1L2 f L L1L2 f L LV f L1L2V L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2

343.52 348.58

9.781 10.241

L1L2V f L1L2 L1L2V f L1L2

363.64 368.64

10.971 11.211

LV f L1L2V LV f L1L2V

338.56 343.54 348.55 353.55 358.60 363.64 368.76 290.98 293.52 295.97 298.43 303.47 308.43 313.51 318.41 323.51 325.92 278.53 283.47 288.55 322.41 323.09 324.82 328.05 329.67 331.21 334.48 339.28 344.66 348.18 353.04 357.61 363.09 366.69 281.52 289.27 295.23 297.06

9.346 9.826 10.291 10.741 11.146 11.556 11.926 11.786 10.701 9.921 9.386 8.896 8.996 9.486 10.251 11.261 11.796 3.302 3.782 4.252 7.915 8.010 8.195 8.535 8.705 8.885 9.215 9.740 10.270 10.610 11.045 11.445 11.890 12.165 3.638 4.352 4.932 5.107

L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L L1L2 f L LV f L1L2V LV f L1L2V LV f L1L2V L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 L1L2V f L1L2 LV f L1L2V LV f L1L2V LV f L1L2V LV f L1L2V

290.98 293.54 295.97 298.43 303.46 308.43 313.46 318.42 323.50 325.92 328.44 333.47 338.55 343.54 348.55 353.54 358.56 363.63 368.75

4.467 4.722 4.956 5.196 5.696 6.196 6.706 7.206 7.726 7.971 8.211 8.671 9.141 9.556 9.946 10.301 10.616 10.891 11.131

LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV

f f f f f f f f f f f f f f f f f f f

L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V

299.16 300.94 304.82 310.52 313.42 317.99 322.40 323.10 329.67 334.48 339.25 344.68 348.19 353.03 357.62 363.07 366.70

5.317 5.497 5.887 6.472 6.772 7.242 7.687 7.762 8.407 8.867 9.292 9.692 10.017 10.367 10.667 10.977 11.162

LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV LV

f f f f f f f f f f f f f f f f f

L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V L1L2V

The mole fraction of [hmim+][BF4-] in 2-propanol is kept constant at 4.72% (ratio 2-propanol:[hmim+][BF4-] ) 20:1).

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ReceiVed for reView September 8, 2009 ReVised manuscript receiVed February 7, 2010 Accepted February 17, 2010 IE901405P