Ionic liquids molar volumes

In 1999 Blanchard et al. reported a good solubility of carbon dioxide in l-butyl-3-methylimidazolium hexafluorophosphate at high pressures, while the ionic liquid did not dissolve in carbon dioxide. Therefore, supercritical carbon dioxide is suited to extract organic solutes from ionic liquids, and also continuous flow homogeneous catalysis in ionic liquids carbon dioxide systems is possible. First spectroscopic studies show that the anion dominates the interactions with carbon dioxide by Lewis acid-base interactions. However, the strength of carbon dioxide anion interactions did not correlate with carbon dioxide solubility. Thus, strong anion-carbon dioxide interactions were excluded as major cause for the carbon dioxide solubility in ionic liquids. Instead, a correlation of carbon dioxide solubility and the ionic liquid molar volume was observed. Additionally, a significant volume decrease of dissolved carbon dioxide was... 

Marcus Y (2015) Ionic and molar volumes of room temperature ionic liquids. J Mol Liq 209 289-293... 

Reaction conditions aUcenerCOrEL = 1 1 1, T = 100 °C, 0.2 wt% Rh metal loading, silica 100 p = 10 bar for guanidinium and norbos-Cs, p = 5 bar for sulfoxantphos ionic liquid used for impregnation [BMIM][PF6] a) molar ligand to metal ratio b) ratio of ionic liquid volume to support pore volume c) mol aldehyde per mol rhodium per hour d) ratio between linear and branched aldehyde e) support loaded with ionic liquid only. 

Table 1.3 Molar Volume, V, at 298.15 K of Several Ionic Liquids...

Zafarani-Moattar, M.T. and Shekaari, H. Volumetric and speed of sound of ionic liquid, l-butyl-3-methylimidazolium hexafluorophosphate with acetonitrile and methanol at T = (298.15 to 318.15) K, /. Chem., Eng. Data, 50,1694,2005. Wang, J. et al.. Excess molar volumes and excess logarithm viscosities for binary mixtures of the ionic liquid l-butyl-3-methylimidazolium hexafluorophosphate with some organic solvents, /. Solution Chem., 34, 585, 2005. 

Heintz, A. et al.. Excess molar volumes and liquid-liquid equilibria of the ionic liquid l-methyl-3-octyl-imidazolium tetrafluoroborate mixed with butan-l-ol and pentan-l-ol, /. Solution Chem., 34,1135, 2005. 

Figure 2.10 Dependence of the cohesion of salts of weakly polarizable cations and anions, assessed by Tg value, on the ambient temperature molar volume hence on interionic spacing [(r -i- r) V ]. A broad minimum in the ionic liquid cohesive energy is seen at a molar volume of 250 crrPnmr, which corresponds to an interionic separation of about 0.6nm, assuming face-centered cubic pacidng of anions about cations. The lowest Tg in the plot should probably be excluded from consideration because of the non-ideal Walden behavior for this IL (MOMNMgE BF ) [15]). The line through the points is a guide to the eye. The data for open triangles are from Sun, Forsyth, and MacFatlane [42].

Bhujrajh P, Deenadayalu N. Liquid densities and excess molar volumes for binary systems (ionic liquids plus methanol or water) at 298.15, 303.15 and 313.15K, and at atmospheric pressure. J. Solut. Chem. 2007. 36, 631-642. 

Heintz A, Klasen D, Lehmann J K. Excess molar volumes and viscosities of binary mixtures of methanol and the ionic liquid 4-methyl-N-butylpyridinium tetrafluoroborate at 25, 40, and 50 °C. J. Solution Chem. 2002. 31, 467-476. 

Zaitsau et al. [44] measured the vapor pressure of a series of [C mim NTf2] ionic liquids using the integral effusion Knudsen method and correlated the A H with the molar volumes and the surface tensions of the compounds. What is clear from this study is that the values for A H are approximately half that used in Rebelo s initial estimate and further indicated that the Eotvos-Guggenheim correlations which are suitable for molecular solvents do not apply for ionic liquids. 

A number of models which can estimate density at atmospheric pressure have recently been reported. For example, Rebelo et al. [63, 64] defined the effective molar volumes of ions at 298.15 K and used the assumption of ideal behavior for the determination of the molar volume of ionic liquids. Yang et al. [65] used a theory based on the interstice model which correlated the density and the surface tension of the ionic liquid. Group contribution models have been reported by Kim et al. [66, 67] for the calculation of the density and C02 gas solubility for 1-alkyl-3-methylimidazolium based ionic liquids as a function of the temperature and C02 gas pressure with reasonable accuracy over a 50 K temperature range however, the... 

Table 3 Impact of water impurities on the calculated molar volume of ionic liquids...

Recently Jacquemin et al. [61,71] extended the concept proposed by Rebelo et al. In this method the effective molar volume of an ionic liquid and hence density can be determined by assuming that the volumes of the ions behave as an ideal mixture. This strategy was used to calculate the effective molar volumes of a wide range of ions using a large set of previously reported data as a function of the temperature difference at 0.1 MPa and a reference temperature of 298.15 K using the following equation ... 

Fig. 5 Predicted vs experimental molar volumes for a range of ionic liquids at varying temperature and pressure using the group contribution method proposed by Jacquemin et al. [72]...

One important solute is water, which is completely miscible in imidazolium salts with short alkyl side chains and hydrophilic anions such as d, but is only partially miscible with ionic liquids with longer side chains and less hydrophilic anions. Extraction into an aqueous phase is important for product recovery from an ionic liquid medium. Hanke and Lynden-BeU [143] used simulation to investigate thermodynamic properties and local structure in mixtures of water with [MMIM]Q and [MMIM][PF6] liquids. They found that the excess energy of solvation was negative for the chloride and positive for the [PF ]" liquid, as shown in Fig. 4.2-12. There is a similar difference in the molar volumes of mixing shown in Fig. 4.2-13. This is consistent with the perception of the [PFe]" anion as being more hydrophobic than the chloride anion. 

Marcus Y (2012a) The standard partial molar volumes of ions in solution. Part 5. Ionic volumes in water at 125-200 °C. J. Phys. Chem. B 117 http //dx.doi/10.1021/jp212518t Marcus Y (2012b) Are ionic Stokes radii of any use J. Solution Chem in the press Marcus Y, Hefter G (1999) On the pressure and electric field dependencies of the relative permittivity of liquids. J Sol Chem 28 575-591 Marcus Y, Hefter G (2006) Ion pairing. Chem Rev 106 4585-4621... 

J. Kumelan, D. Tuma, G. Maurer, Partial molar volumes of selected gases in some ionic liquids. Fluid Phase Equilibria, 275, 132-144 (2009). 

Borodin O (2009) Relation between heat of vaporization, ion transport, molar volume, and cation and anion binding energy for ionic liquids. J Phys Chem B 113 12353... 

For (12), it is assumed that the volume of the micellar phase is proportional to the tenside concentration and that the partial molar volume v remains constant. It is also assumed that the ionic mobility of the micellar phase does not change on taking up a solute (Mmc = constant). In contrast to high-performance liquid chromatography (HPLC), substances which have an infinitely high kp value, that is, which are completely dissolved in the micellar phase, can be detected. In this case, the sample molecule migrates with the mobility of the micelle. 

The molar conductivity Am of the liquid salt is obtained from the specific conductivity k and the molar volume Vm (Eq. Id) of the salt that is available from density measurements. The modified Walden rule is applied for comparing ILs. The deviation from the Walden rule represented by a is interpreted in terms of ionic-ity. A small ionicity is caused by strong ion-ion interaction. 

Hanke and Lynden-Bell carried out another study of water dissolved in hydrophilic [Cimim][Cl] and hydrophobic [CimimJlPFg] in which isochoric-isothermal MD simulations were run at 127°C on mixtures containing water mole fractions of 0.05, 25, 50, 75, and 99.5%. They computed excess volumes, enthalpies, and internal energies of mixing and compared the results between the two ionic liquids and found that the excess properties between the two systems differed qualitatively, as might be expected. Unfortunately, no experimental data was available for these systems against which to compare their results. The authors pointed out, however, that the magnitude of computed quantities such as excess molar volumes were consistent with those for other ionic liquid systems for which data was available. 

Various physical properties of ionic liquids, as viscosity and molar concentration, are directly dependent on the sum of the ionic volumes of cation and anion.l l In this light, it is interesting to consider the effect of the choice of the ionic liquid. The size of the nanoparticles frequently increases with increasing molecular volume (or size) of the (weakly) coordinating anion (BF4-, PFe" and Tf2N ), e.g., for Ag nanoparticles from 2.5 to 27 nm and for W nanoparticles from 1.5 to 30 nm. ... 

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