Measurement and modeling the excess molar properties of binary mixtures of {[C6mim][BF4] + 3-amino-1-propanol} and {[C6mim][BF4] + isobutanol}: Application of Prigogine–Flory–Patterson theory

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Abstract

In this work, densities, ρ, and viscosities, η, of pure 1-hexyl-3-methylimidazoliumtetrafluoro borate {[C6mim][BF4]}, 3-amino-1-propanol (AP), and isobutanol, along with their binary mixtures of {x1[C6mim][BF4] + x2AP} and {x1[C6mim][BF4] + x2isobutanol} were measured over entire composition range at ambient pressure (81.5 kPa) and in the temperature range of (303.15 to 338.15) K. The excess molar volume, VmE, thermal expansion coefficient, α, and its excess value, αE, isothermal coefficient of excess molar enthalpy, (HmE/p)T,x, and viscosity deviation, Δη, for both of the mixtures were calculated from the experimental values of densities and viscosities. The values of VmE for binary mixture of {x1[C6mim][BF4] + x2AP} shows a S-shaped dependence on composition with positive values in the [C6mim][BF4] rich-region and negative values at the opposite extreme, and increase with increasing temperature. This quantity is negative for binary mixture of {x1[C6mim][BF4] + x2isobutanol} in the entire composition range and increases with increasing temperature. Viscosity deviations, Δη, are negative over the entire composition range and decrease with increasing temperature for both of the mixtures. These data were correlated by Treszczanowiczb–Benson and Redlich–Kister equations, and the fitting parameters and standard deviations were determined. The Prigogine–Flory–Patterson theory has been used to correlate the excess molar volumes of the mixtures.

Highlights

► Densities and viscosities of binary mixtures of {x1[C6mim][BF4] + x2AP} and {x1[C6mim] [BF4] + x2isobutanol} were measured at different compositions and temperatures. ► The excess molar functions were calculated from these experimental data. ► The obtained excess molar volumes were correlated with PFP theory.

Introduction

Ionic liquids (ILs) are ionic solvents with negligible vapor pressure which distinguishes them from molecular solvents [1], [2]. They are important solvents for their high thermal stability, high ionic conductivity, and high solvating capacity for both polar and non polar compounds. They have known for their no volatility and no flammability. They have been accepted as “green solvents” due to their recyclability. All these characteristics make ILs to be suitable compounds in making various instruments such as sensors, fuel cells, batteries, capacitors, and as solvent in analysis, synthesis, catalytic reactions, and separation processes. Therefore, study of physiochemical properties of ILs and their mixtures has been an important subject in recent years [3], [4], [5]. Also, the interactions that exist between ILs with polar and non-polar solvents have been studied via excess thermodynamic properties by some investigators [6], [7], [8], [9], [10].

In the present work, density, ρ, and viscosity, η, of pure components [C6mim][BF4], AP, isobutanol, and their binary mixtures of {x1[C6mim][BF4] + x2AP} and {x1[C6mim][BF4] + x2isobutanol} were measured over entire composition range and in the temperature range of (303.15 to 343.15) K. These quantities were used to calculate the excess molar volumes, VmE, and the viscosity deviations, Δη, and the results were correlated with the Treszczanowicz–Benson equation [11] for VmE and Redlich–Kister [12] equation for the other quantities. The obtained VmE values were also correlated by Prigogine–Flory–Patterson (PFP) model [13].

Section snippets

Chemicals

The materials were purchased from Merck Company with purities in mass fraction >99.8% for [C6mim][BF4] and >99% for AP and isobutanol, and have been used without further purification. The purities of the components were verified by measuring the densities and viscosities, which were in good agreement with the values reported in the literature [9], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], as are listed in table 1. The water mass fraction of the IL was determined by Karl

Volumetric properties of mixtures

The densities of pure components [C6mim][BF4], AP, and isobutanol were measured in the temperature range of (303.15 to 338.15) K with an interval of 5 K and the obtained results are listed in table 1. The densities of binary mixtures of {x1[C6mim][BF4] + x2AP} and {x1[C6mim] [BF4] + x2isobutanol} were measured over the entire concentration range from temperature (303.15 to 338.15) K. The excess molar volumes of the binary mixtures were calculated from the measured densities using the following

Conclusions

Densities of binary mixtures of {x1[C6mim][BF4] + x2AP} and {x1[C6mim][BF4] + x2isobutanol} were measured over entire composition range in the temperature range of (303.15 to 338.15) K. Data of the excess molar volumes, VmE, thermal expansion coefficients, α, and their excess values, αE, and isothermal coefficient of excess molar enthalpy (HmE/p)T,x for both of binary mixtures were calculated from the experimental densities data. The value of VmE for binary mixture of {x1[C6mim][BF4] + x2AP} shows a

Acknowledgement

The Research Council of Bu-Ali Sina University for financial support of the work should be appreciated.

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