Abstract
The effects of temperature and composition on the density and viscosity of pure benzothiophene and ionic liquid (IL), and those of the binary mixtures containing the IL 1-butyl-1-methylpyrrolidynium tricyanomethanide ([BMPYR][TCM] + benzothiophene), are reported at six temperatures (308.15, 318.15, 328.15, 338.15, 348.15 and 358.15) K and ambient pressure. The temperature dependences of the density and viscosity were represented by an empirical second-order polynomial and by the Vogel–Fucher–Tammann equation, respectively. The density and viscosity variations with compositions were described by polynomials. Excess molar volumes and viscosity deviations were calculated and correlated by Redlich–Kister polynomial expansions. The surface tensions of benzothiophene, pure IL and binary mixtures of ([BMPYR][TCM] + benzothiophene) were measured at atmospheric pressure at four temperatures (308.15, 318.15, 328.15 and 338.15) K. The surface tension deviations were calculated and correlated by a Redlich–Kister polynomial expansion. The temperature dependence of the interfacial tension was used to evaluate the surface entropy, the surface enthalpy, the critical temperature, the surface energy and the parachor for pure IL. These measurements have been provided to complete information of the influence of temperature and composition on physicochemical properties for the selected IL, which was chosen as a possible new entrainer in the separation of sulfur compounds from fuels. A qualitative analysis on these quantities in terms of molecular interactions is reported. The obtained results indicate that IL interactions with benzothiophene are strongly dependent on packing effects and hydrogen bonding of this IL with the polar solvent.Electronic supplementary materialThe online version of this article (doi:10.1007/s10953-014-0257-1) contains supplementary material, which is available to authorized users.
Highlights
New international regulations require the removal of low level sulfur compounds such as thiophene, benzothiophene, methyldibenzothiophenes, 4,6-dibenzothiophenethiols, thioethers, and disulfides from fuels
We report an experimental investigation of the density, viscosity and surface tension for the pure ionic liquid (IL), [BMPYR][TCM], and benzothiophene, as well as of binary mixtures containing ([BMPYR][TCM] ? benzothiophene) as a function of temperature and composition at ambient pressure
Negative deviations in the range of measured mole fraction were observed for the excess molar volumes, VmE, and positive deviations were observed for both the excess dynamic viscosity, Dg, and surface tension deviation, Dr The results show that addition of benzothiophene increases the density but decreases the viscosity and surface tension of the mixture, which results in a loss of structural order at the interface and in the bulk of the IL
Summary
New international regulations require the removal of low level sulfur compounds such as thiophene, benzothiophene, methyldibenzothiophenes, 4,6-dibenzothiophenethiols, thioethers, and disulfides from fuels. It is a challenge to design ILs that incorporate progressively larger extraction selectivity, while maintaining viscosity, density and surface tension convenient for a new technology. We have just reported experimental ternary LLE data for three ILs, which we expected to show high selectivity for the extraction of thiophene: 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate, [BMPYR][CF3SO3], 1-butyl-1-methylpyrrolidinium tricyanomethanide, [BMPYR][TCM], and 1-hexyl-3-methylimidazolium tetracyanoborate, [HMIM][TCB] [14]. Very good results for the extraction of sulfur compounds from model mixtures of real fuels were obtained with tricyanomethanide-based, [TCM]-, ILs [7]. The current work represents a continuation of our systematic study on desulfurization of fuels and physicochemical properties of ILs. We report an experimental investigation of the density, viscosity and surface tension for the pure IL, [BMPYR][TCM], and benzothiophene, as well as of binary mixtures containing The data obtained were analyzed to determine the effect of temperature on fundamental physicochemical and thermodynamic properties
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