High-Pressure Densities and Derived Thermodynamic Properties of Imidazolium-Based Ionic Liquids

Gardas, Ramesh L.; Freire, Mara G.; Carvalho, Pedro J.; Marrucho, Isabel M.; Fonseca, I.M.A.; Ferreira, A.G.M.; Coutinho, João A. P.

doi:10.1021/je060247x

Cited by 390 publications

(328 citation statements)

References 29 publications

Supporting

Mentioning

283

Contrasting

Order By: Relevance

“…As for the anion influence on the relative interaction strength, a general trend can be established between the cation-anion interaction and the anion molar volumes: the former decreases as the molar volume increases. 16,54 The relevance of these results to the understanding of the measured mutual solubilities is discussed below.…”

Section: Resultsmentioning

confidence: 92%

See 1 more Smart Citation

Mutual Solubilities of Water and Hydrophobic Ionic Liquids

et al. 2007

Self Cite

View full text Add to dashboard Cite

The ionic nature of ionic liquids (ILs) results in a unique combination of intrinsic properties that produces increasing interest in the research of these fluids as environmentally friendly "neoteric" solvents. One of the main research fields is their exploitation as solvents for liquid-liquid extractions, but although ILs cannot vaporize leading to air pollution, they present non-negligible miscibility with water that may be the cause of some environmental aquatic risks. It is thus important to know the mutual solubilities between ILs and water before their industrial applications. In this work, the mutual solubilities of hydrophobic yet hygroscopic imidazolium-, pyridinium-, pyrrolidinium-, and piperidinium-based ILs in combination with the anions bis-(trifluoromethylsulfonyl)imide, hexafluorophosphate, and tricyanomethane with water were measured between 288.15 and 318.15 K. The effect of the ILs structural combinations, as well as the influence of several factors, namely cation side alkyl chain length, the number of cation substitutions, the cation family, and the anion identity in these mutual solubilities are analyzed and discussed. The hydrophobicity of the anions increases in the order [C(CN) 3 ] < [PF 6 ] < [Tf 2 N] while the hydrophobicity of the cations increases from [C n mim] < [C n mpy] e [C n mpyr] < [C n mpip] and with the alkyl chain length increase. From experimental measurements of the temperature dependence of ionic liquid solubilities in water, the thermodynamic molar functions of solution, such as Gibbs energy, enthalpy, and entropy at infinite dilution were determined, showing that the solubility of these ILs in water is entropically driven and that the anion solvation at the IL-rich phase controls their solubilities in water. The COSMO-RS, a predictive method based on unimolecular quantum chemistry calculations, was also evaluated for the description of the water-IL binary systems studied, where it showed to be capable of providing an acceptable qualitative agreement with the experimental data.

show abstract

Section: Resultsmentioning

confidence: 92%

“…[14][15][16] Water may also act as a cosolvent, for example, increasing the mutual solubilities between alcohols and ILs, or as an antisolvent, reducing the solubility of gases in ILs. [17][18][19][20] The presence of water can also affect the rates and selectivity of reactions involving or carried in ILs.…”

Section: Introductionmentioning

confidence: 99%

Mutual Solubilities of Water and Hydrophobic Ionic Liquids

et al. 2007

Self Cite

View full text Add to dashboard Cite

show abstract

“…28 The reagents [C n mim]-[Br] (n ) 2 to 8) and [Li][Tf 2 N] were acquired at IoLiTec with purities of >99% and >98%, respectively. In order to reduce the water content and volatile compounds to negligible values, the ILs individual samples were dried under constant agitation at vacuum (0.1 Pa) and at 353 K, for a minimum of 48 h. After that careful procedure, the ILs purities were checked by 1 H, 13 C, and 19 F NMR spectroscopy being >99% for all ILs. The bromide content was quantified by ion chromatography and was inferior to 100 × 10 -6 in mass fraction for all samples.…”

Section: Methodsmentioning

confidence: 99%

“…[6][7][8][9][10] Another factor that makes the knowledge of mutual solubility with water of importance is the way how the presence of water in the ionic liquids can dramatically affect their physical properties such as viscosities, densities, and surface tensions. [11][12][13] Water may also acts as a cosolvent increasing the mutual solubilities between alcohols and ILs 11,14,15 or as an antisolvent reducing the solubility of other compounds, for example, gases and nonpolar compounds, in ionic liquids. 16,17 Furthermore, the presence of water also affects the rates and selectivity of reactions involving or carried out in ILs.…”

Section: Introductionmentioning

confidence: 99%

Mutual Solubilities of Water and the [C_nmim][Tf₂N] Hydrophobic Ionic Liquids

et al. 2008

Self Cite

View full text Add to dashboard Cite

Ionic liquids (ILs) have recently garnered increased attention because of their potential environmental benefits as "green" replacements over conventional volatile organic solvents. While ILs cannot significantly volatilize and contribute to air pollution, even the most hydrophobic ones present some miscibility with water posing environmental risks to the aquatic ecosystems. Thus, the knowledge of ILs toxicity and their water solubility must be assessed before an accurate judgment of their environmental benefits and prior to their industrial applications. In this work, the mutual solubilities for [C 2 -C 8 mim][Tf 2 N] (n-alkyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)imide) and water between 288.15 and 318.15 K at atmospheric pressure were measured. Although these are among the most hydrophobic ionic liquids known, the solubility of water in these compounds is surprisingly large, ranging from 0.17 to 0.36 in mole fraction, while the solubility of these ILs in water is much lower ranging from 3.2 × 10 -5 to 1.1 × 10 -3 in mole fraction, in the temperature and pressure conditions studied. From the experimental data, the molar thermodynamic functions of solution and solvation such as Gibbs energy, enthalpy, and entropy at infinite dilution were estimated, showing that the solubility of these ILs in water is entropically driven. The predictive capability of COSMO-RS, a model based on unimolecular quantum chemistry calculations, was evaluated for the description of the binary systems investigated providing an acceptable agreement between the model predictions and the experimental data both with the temperature dependence and with the ILs structural variations.

show abstract

“…Ammonium [67], phosphonium [68] and guanidinium [69] based ILs were also studied. It was observed that the increase of alkyl chain in 1-alkyl-3-methylimidazolium provokes a correspondent decrease on density values as described by Esperança et al [68] and Gardas [70] et al Both independent studies reported a constant augment of the molar volume of the salt per each two -CH 2 -groups (34.4 cm 3 .mol -1 and 33.88 cm 3 .mol -1 , respectively). This progressive augment of molar volume leads to the decrease of density.…”

Section: Relationship Between Structure and Densitymentioning

confidence: 64%