Physicochemical Characterization of Two Protic Hydroxyethylammonium Carboxylate Ionic Liquids in Water and Their Mixture

Journal article (2022)

Authors

F.A. Ferrari BT/Bioprocess Engineering - AS , University of Campinas
Malaret Francisco Imperial College London
S.J. Eustace BT/Biocatalysis - AS
Hallett Jason Imperial College London
L.A.M. van der Wielen BT/Bioprocess Engineering - AS
G. J. Witkamp King Abdullah University of Science and Technology
Forte Marcus Bruno University of Campinas
Research Group
BT/Biocatalysis (AS) (TU Delft)
Copyright: © 2022 F.A. Ferrari, Malaret Francisco, S.J. Eustace, Hallett Jason, L.A.M. van der Wielen, Witkamp Geert-Jan, Forte Marcus Bruno
DOI
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https://doi.org/10.1021/acs.jced.1c00687
More Info
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Published Date

2022

Language

English

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Faculty

Applied Sciences

Department

BT/Biotechnologie

Research Group

BT/Biocatalysis

Abstract

A systematic study on the physicochemical properties of two protic ionic liquids (ILs) {2-hydroxyethylammonium acetate ([Mea][Ac]) and 2-hydroxyethylammonium hexanoate ([Mea][Hex])} and their mixtures with water was performed. The density and viscosity were assessed across the entire range of aqueous dilutions between 278 and 393 K. The conductivities, water activities, and surface tension of the binary systems in water were also assessed, and the influence of anions was evaluated. Differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), and 1H and 13C nuclear magnetic resonance (NMR) techniques were used to study the systems at different IL compositions. The excess molar volumes (VE) and thermal expansion coefficients were calculated, with negative values for VE across the entire concentration range. Density data were fitted to a polynomial for density prediction, function of temperature, and concentration, with the average deviation percentage not exceeding 0.63%. The viscosities of the binary systems were studied considering six different models and were better predicted by the model of Herráez et al. at IL concentrations higher than 0.25 mole fraction. The systems containing [Hex]- exhibited higher water activities and lower conductivity and surface tension. All studied systems exhibited a glass transition event, which varied according to the IL composition. The FTIR and NMR analysis confirmed the distinct molecular arrangement of [Mea][Ac] and [Mea][Hex] systems.