Volumetric and transport properties of N-Butyl-N-methylpyrrolidinium bis(Trifluoromethanesulfonyl)imide–methanol binary mixtures

Abstract

Densities, viscosities, and ionic conductivities were measured for the binary mixtures containing the ionic liquid Nbutyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide and methanol over the entire range of compositions at the temperature varying from 253.15 to 318.15 K. The densities and viscosities decrease monotonously with temperature and the content of ionic liquids (ILs). Furthermore, excess isobaric expansion coefficient has been calculated from the experimental densities. The dependence of temperature on the viscosity has been fitted to the Arrhenius law with high precision. The dependence of temperature on the ionic conductivity has also been gauged by both of the Arrhenius and Vogel-Tamman-Fulcher (VTF) equations. In fact, the shape of the curves shows that the temperature dependence of the conductivity does not follow a simple Arrhenius law, but a better fitting of experimental results is achieved using the VTF model. Additionally, the effects of ILs concentration on the viscosity and the conductivity have been examined using the Walden rule, which shows that the variation of conductivity is inversely proportional to viscosity. Excess molar volumes and viscosity deviations for all mixtures are evaluated and well fitted to the Redlich-Kister polynomial expansions. Physicochemical properties show two clearly distinguished behaviors corresponding to ILsrich and methanol-rich regions, with distinct transport and volumetric properties. The obtained results are discussed in terms of dipolar interactions and hydrogen bonding establishment between ions of ILs and the methanol molecules.

Ionic Conductivities of Binary Mixtures Containing Pyridinium-Based Ionic Liquids and Alkanols

“…As these plots show, the ionic conductivity increases when the temperature rises in all the systems, because temperature produces an increment of the mobility of the ions. 11,13 It is also remarkable that ionic conductivities of the mixtures are higher than pure compounds values. 11,14 All the experimental curves have the same shape and can be divided in two parts which are separated by the maximum of the graph: at high ionic liquid concentrations, ionic conductivities are small because the viscosity of the mixture is too large, when small quantities of the organic solvent are added, the viscosity decreases and the mobility of charge carriers rises, consequently ionic conductivity continuously increases until it reaches its maximum.…”

“…10 However, the experimental measurements of the ionic conductivity of liquid mixtures containing ILs are scarce in the literature. Zarrougui et al 11 presented a study of volumetric and transport properties of N-butyl-N-methylpyrrolidinium bis trifluoromethanesulfonyl imide with methanol in the temperature range 253.15 K to 318.15 K. Toumi et al 12 studied the ionic conductivity as a function of temperature for the liquid mixture triethylamine plus KCl aqueous solution. Zhang et al 13 measured the ionic conductivity of solutions of pyridinium based ionic liquids with methanol, ethanol, acetonitrile, and propylene carbonate.…”

State of Hydrophobic and Hydrophilic Ionic Liquids in Aqueous Solutions: Are the Ions Fully Dissociated?

“…The authors assumed a complete dissociation of the IL into ions to explain the anomalous behavior. In the study by Zarrougui et al, 19 the authors reported viscosities and ionic conductivities of IL− methanol mixtures and noted that the viscosity of the mixture increases marginally up to an IL concentration of 1. increases dramatically for concentrations exceeding this limit.…”

“…The authors assumed a complete dissociation of the IL into ions to explain the anomalous behavior. In the study by Zarrougui et al, the authors reported viscosities and ionic conductivities of IL–methanol mixtures and noted that the viscosity of the mixture increases marginally up to an IL concentration of 1.5 M but increases dramatically for concentrations exceeding this limit. Similarly, the ionic conductivity shows an increase to 1.1 M IL concentration, beyond which the conductivity decreases.…”

Measurement and Correlation of the Electrical Conductivity of the Ionic Liquid [BMIM][TFSI] in Binary Organic Solvents

“…Ionic liquid is usually mixed with organic solvents to reduce viscosity and improve electrical conductivity. − For example, Rilo et al dissolved 1-alkyl-3-methyl imidazolium tetrafluoroborate ([C n MIM]­[BF 4 ], n = 2, 4, 6, 8) in ethanol and found the electrical conductivity of the solution was significantly improved compared to the pure IL. Zarrougui et al measured the electrical conductivity of N -butyl- N -methylpyrrolidinium bis­(trifluoro-methanesulfonyl) imide ([Pyr 14 ]­[TFSI]) + methanol mixture, and they found there was a maximum value of electrical conductivity for the solution. Similarly, dissolved ionic liquid in mixed organic solvents can also improve the performance of the electrolyte.…”