Thermophysical study of binary mixtures of 1-butyl-3-methylimidazolium nitrate ionic liquid + alcohols at different temperatures

https://doi.org/10.1016/j.jct.2019.04.010Get rights and content

Highlights

  • Densities and viscosities of IL + 2-alkanol mixtures were measured.

  • Partial molar volumes and thermal expansibility for mixtures were calculated.

  • All data of binary mixtures are new and reported for first time.

Abstract

New experimental data of density and viscosity for the binary mixtures of 1-butyl-3-methylimidazolium nitrate ([Bmim][NO3]) with + 2-propanol, 2-butanol and 2-pentanol are reported over the entire range of mole fraction at T = (293.15–323.15) K. To elucidate possible intermolecular interactions between the chemical species present in solutions, the excess molar volume, VmE thermal expansion coefficient, α excess thermal expansion coefficient, αE the isothermal coefficient of excess molar enthalpy, HmE/PT,x partial molar volume, Vi¯ and deviation in viscosity, Δη were calculated. The excess molar volume of the binary mixture is negative over the entire mole fraction range and becomes more negative with increase in the temperature. Deviation in the viscosity is negative over the whole range of composition and decreases with increasing temperature. The obtained excess molar volume and deviation in viscosity were fitted to the Redlich–Kister polynomial equation. The experimental results have been discussed regarding molecular interactions and the formation of complex between unlike molecules. Influences of temperature and carbon chain length of alcohols were discussed.

Introduction

Ionic liquids (ILs), as green solvents, have attracted amazing interest and their potential applications have prompted a large amount of research and investment. The possibility of different combinations of ions leads to the production of ionic liquids with different features and applications in recent years. As a result, the knowledge of pure ionic liquids properties and their solutions shows great importance in many technological applications. Due to their properties, ILs have been used as potential solvents in many processes such as nanotechnology, electrolytic cells, and heat transfer fluids. The most important properties of ILs that have aroused interest in the application of these compounds are their negligible vapor pressure and high chemical and thermal stability [1]. The knowledge of the thermophysical properties of pure ILs and their solutions such as density and viscosity and the excess parameters derived from them are fundamental in the chemical process industry, especially those involving chemical separations and mass flow. The [Bmim][NO3] is a halogen-free IL, relatively hydrolysis-stable compound and more environment–friendly. Furthermore, nitrate-based ionic liquids are successfully utilized as an interesting medium for dissolution and stabilization of metal salts and could be an interesting alternative for industrial application because they avoid the liberation of toxic and corrosive HF into the environment [2]. In this paper, liquid densities and viscosities of pure 1-butyl-3-methylimidazolium nitrate ([Bmim][NO3]) and its binaries with 2-propanol, 2-butanol and 2-pentanol were measured at seven temperatures (293.15–323.15 K) within the entire composition range. To our knowledge, there are no data reported for its binaries with mentioned alcohols.

Section snippets

Compounds

The ionic liquid [Bmim][NO3] (purity ≥ 0.98) was purchased from the Chemistry and Chemical Engineering Research Center in Iran. Since the physical properties of ionic liquids are sensitive to impurities and water content, The IL was dried and degassed for 24 h at T = 343.15 K under vacuum and was kept in a bottle under Argon gas to separate it from the volatile byproducts or water, and subsequently put in a purified argon atmosphere. The water content of IL estimated by Karl Fischer titration

Densities and excess molar volumes

The experimental values of densities for binary mixtures at various temperatures are listed in Table 3. Binary densities and viscosities decrease as a function of temperature and increase with increasing alcohols chain length. The volumetric properties are closely related with the volume change of substance, such as density, partial molar volume, excess molar volume, and expansibility. Mentioned properties provide significant information for engineering design and optimization. The excess molar

Concluding remarks

Experimental density and viscosity of pure [Bmim][NO3] and its binaries with 2-propanol, 2-butanol and 2-pentanol were measured in the temperature range of 293.15–323.15 K. The excess molar volume and deviation in viscosity show negative behavior from the ideal solution. Excess molar volume becomes more negative with increasing temperature that can be attributed to the fact that increasing temperature expands the volume of the mixture, so more spaces between IL molecules will be available for

Acknowledgements

The author thanks the Islamic Azad University (Omidiyeh Branch) and Malayer University for providing the facilities to carry out this work.

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