(377m) Volumetric, Acoustic and Viscometric Properties of Binary Mixture of (n-butylammonium methanoate + 1-butanol) at Different Temperatures

Ionic liquids (ILs) are salt melts comprised solely of ions and exhibit very low melting points compared to classical molten salts. The term “IL” is commonly used when the melting point is equal to, lower than 100 °C, while “RTIL” specifically refers to ILs with melting points lower than, or equal to room temperature (RT). Nowadays, there are many studies on the physico-chemical analyses of binary mixture of ILs [1]. In this work, experimental data of density, speed of sound and viscosity for binary mixture of {n-butylammonium methanoate + 1-butanol} have been determined as a function of composition at T = (293.15 - 313.15) K. The results were used to calculate the excess molar volume, V^E, deviation in isentropic compressibility, Δk_S , deviation in viscosity, Δη, and excess Gibbs free energy of activation of viscous flow, ΔG^*E, and correlated to the Redlich-Kister polynomial equation. Ionic liquids were synthesized by the method of acid-base neutralization reaction using n-butylamine and methanoic acid [2]. N-butylamine (Merck, purity > 99.0%) and methanoic acid (Merck, purity > 98.0) were used without further purification. Ionic Liquids were characterized by using ¹H-NMR, ¹³C-NMR and FTIR spectroscopy techniques and Karl-Fisher titration. The purity of IL synthesized was 0.997 and the water content was at 0.3%.

The binary mixtures were prepared by weighing the pure components using an electronic balance manufactured by Shimadzu (Model AUY220). The densities and speed of sound of pure components and their solutions were measured using a commercial density and speed of sound analyzer manufactured by Anton Paar (DSA 5000). The viscosities were measuring using a Stabinger viscometer manufactured by Anton Paar (SVM 3000/G2). The analysis of ¹H-NMR and ¹³C-NMR were obtained in an Avance III 600 HD Bruker spectrometer operating at 600 MHz for protons and 150 MHz for carbon. The IR spectra were obtained in Fourier transform infrared spectroscopy Nicolet with attenuated total reflectance (FTIR-ATR) (Model 6700).

For all systems studied, the values of excess molar volumes, deviation in isentropic compressibility and deviation in viscosity were negative over the entire composition range. The values of excess Gibbs energy of activation for viscous flow were positive over the entire composition range. The results obtained were discussed in terms of intermolecular interactions, particularly hydrogen-bonding interactions between like and unlike molecules.

References

[1] Bittencourt, S. S.; Hoga, H. E.; Torres R. B.; D´Angelo, J. V. H. Thermodynamic and spectroscopic properties of binary mixtures of n-butylammonium butanoate ionic liquid with alcohols at T = (293.15 - 313.15) K. The Journal of Chemical Thermodynamics, v. 105, p. 238-252, 2017.

[2] Neto, J. C. A.; Cabral, A. S.; Oliveira; L. R. D.; Torres, R. B. Morandim-Giannetti, A. A., Synthesis and characterization of new low-cost ILs based on butylammonium cation and application to lignocellulose hydrolysis, Carbohydrate Polymers, v. 143, p. 279-287, 2016.