Thermophysical Properties of Five Acetate-Based Ionic Liquids

Ionic liquids (ILs) with improved hydrogen-bonding acceptor abilities, such as acetate-based compounds, have shown great potential for CO₂ capture and biomass dissolution. In this context, the knowledge of the thermophysical properties of acetate-based fluids is essential for the design and scale-up of related processes. However, at this stage, acetate-based ILs are still poorly characterized. In this work, four thermophysical properties, specifically, density, viscosity, refractive index, and surface tension, were determined for five acetate-based ILs. Both protic and aprotic ILs were investigated, namely, N,N-dimethyl-N-ethylammonium acetate, 1-ethylimidazolium acetate, 1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium acetate, and 1-butyl-1-methylpyrrolidinium acetate. From the temperature dependence of the measured properties, additional properties, such as the isobaric thermal expansion coefficient, the surface entropy and enthalpy, and the critical temperature, were further estimated.