Carlos Lafuente

Thermophysic comparative study of two isomeric pyridinium-based ionic liquids.

A comprehensive thermophysical study of isomeric room-temperature ionic liquids n-butyl-3-methyl-pyridinium tetrafluoroborate and n-butyl-4-methyl-pyridinium tetrafluoroborate has been performed. This paper reports various experimental data including density, speed of sound, refractive index, surface tension, isobaric molar heat capacity, and kinematic viscosity. From the experimental results, coefficients of thermal expansion, dynamic viscosities and molar refractions of the studied ionic liquids have been determined. Results have been analyzed paying special attention to the different features of the isomers and their structural differences. Several theories and empirical relations have been applied in order to predict physical properties of ionic liquids. A good agreement between experimental and calculated data has been found. Furthermore, a study about the versatility and application of the different relationships has been carried out finding that in general density and coefficients of thermal expansion can be estimated with relatively good accuracy.

Physicochemical properties of green solvents derived from biomass

Several thermophysical properties (density, refractive index, speed of sound, surface tension, dynamic viscosity, static permittivity and vapour pressure) of five compounds classified as green solvents derived from biomass (furfural, furfuryl alcohol, levulinic acid, ethyl levulinate, butyl levulinate) have been obtained from 278.15 K to 338.15 K. A comparative study has been carried out and information regarding molecular interactions and structure has been obtained.

Anion influence on thermophysical properties of ionic liquids: 1-butylpyridinium tetrafluoroborate and 1-butylpyridinium triflate.

The thermophysical properties of two pyridinium-based ionic liquids, 1-butylpyridinium tetrafluoroborate and 1-butylpyridinium triflate, have been measured. Thus, densities, refractive indices, speeds of sound, viscosities, surface tensions, isobaric molar heat capacities, and thermal properties have been experimentally determined over a wide range of temperatures. The comparison of the properties of the two ionic liquids has allowed us to analyze in detail the anion influence. Moreover, useful derived properties have been calculated from the results. On the other hand, the influence of the lack of a substituent in the cation has been evaluated when properties of 1-butylpyridinium tetrafluoroborate have been contrasted to those of 1-butyl-n-methylpyridinium tetrafluoroborate, (n = 2, 3, or 4). The study has been carried out paying special attention to interactions between ions in order to elucidate the desired relationship between properties and structural characteristics of ionic liquids.

On the viscosity of pyridinium based ionic liquids: an experimental and computational study.

A study on the viscosity of eight pyridinium based ionic liquids is reported for wide pressure and temperature ranges. Measurements were performed using an electromagnetic moving piston viscometer. Experimental data were fitted to a Tait-like equation demonstrating good correlations, which was used to calculate pressure/viscosity and temperature/viscosity coefficients. The effect of the involved anions and cation on the ionic liquid viscosity was analyzed from a molecular viewpoint using hole theory, quantum chemistry calculations using density functional theory, and classical molecular dynamics simulations. The analysis of the experimental and computational results shows the complex effects controlling viscosity of studied fluids, including strength of ionic pairs, molecular sizes, and mobility and effects rising from the availability and cavity sizes distributions in pyridinium-based ionic liquids.

Physicochemical Characterization of n-Butyl-3-methylpyridinium Dicyanamide Ionic Liquid

The room temperature ionic liquid n-butyl-3-methylpyridinium dicyanamide has been characterized. Physicochemical properties such as density, speed of sound, refractive index, surface tension, and kinematic viscosity of the studied liquid have been experimentally measured in a wide range of temperatures. From results, coefficients of thermal expansion, molar refractions, dynamic viscosities and entropies and enthalpies of surface formation per unit surface area at the studied temperatures have been derived. We have analyzed the achieved results for evaluating the effect of the anionic structure in these properties, getting interesting results which lead us to a better understanding of the behavior of the ions in the fluids. Moreover, thermal properties of several pyridinium-based ionic liquids have been investigated. Finally, from both dynamic viscosity values and glass transition temperature of the studied liquids, a detailed analysis of the behavior in fragility terms has been performed.

Excess thermodynamic properties of isomeric butanols with 2-methyl-tetrahydrofuran

Abstract Excess molar volumes, VmE, excess isentropic compressibilities, gkSE, of 1-butanol, 2-butanol, 2-methyl-1-propanol or 2-methyl-2-propanol with 2-methyl-tetrahydrofuran have been determined at the temperatures 298.15 K and 313.15 K. Excess molar enthalpies, HmE, for these mixtures are given at 298.15 K. The results obtained here are compared with those of 1-butanol or 2-butanol with tetrahydrofuran.

Thermophysical study of 1-butyl-2-methylpyridinium tetrafluoroborate ionic liquid.

A thermophysical study of 1-butyl-2-methylpyridinium tetrafluoroborate in a wide range of temperatures has been performed. Thus, density, speed of sound, refractive index, kinematic viscosity, surface tension, and thermal properties have been measured, whereas coefficients of thermal expansion, molar refractions, dynamic viscosities, and entropies and enthalpies of surface formation per unit surface area at the studied temperatures have been calculated. Experimental results have been compared with those obtained for 1-butyl-3-methylpyridinium tetrafluoroborate and 1-butyl-4-methylpyridinium tetrafluoroborate to analyze the effect of the positional isomeric cationic structure on properties. A systematic characterization leads to understand the behavior of such compounds, being a fundamental step to develop their potential as new solvents.

Refractive indices and molar refractions for isomeric chlorobutanes with isomeric butanols

Experimental refractive indices and molar refractions for the binary mixtures of each of the isomers of chlorobutane with each of the isomers of butanol are given at 298.15 K. From these data the refractive index deviations were calculated. The experimental refractive index results were compared with those predicted by several mixing rules: Lorentz–Lorenz, Gladstone–Dale, Arago–Biot, Wiener and Heller.

Excess volumes and excess viscosities of binary mixtures of cyclohexane+picoline

Abstract The densities and viscosities of binary mixtures of cyclohexane + picoline have been measured at 298.15 and 313.15 K over the whole composition range. From these, excess volumes VE, excess viscosities ηE and excess energies of activation for viscous flow G∗E have been calculated. VE is positive and both ηE and G∗E are negative. These results are consistent with the self-association of picolines and the non-polar character of cyclohexane, which produces the dissociation of the picolines.

Thermodynamic and transport properties of binary mixtures containing 1,3-dioxolane

This paper reports density and viscosity measurements for the binary mixtures of cyclopentane or cyclohexane or benzene with 1,3-dioxolane at 283.15, 298.15, and 313.15 K. From the experimental data, excess volumes and excess viscosities were calculated and the results were fitted to a Redlich–Kister-type equation. The results are discussed in terms of molecular interactions. The Prigogine–Flory–Patterson and Blomfield–Dewan theories were used to analyze the results at 298.15 K.