Synthesis and characterization of physical, thermal and thermodynamic properties of ionic liquids based on [C12mim] and [N444H] cations for thermal energy storage

Abstract

This work characterizes the ionic liquids (ILs) [N444H][Cl], [N444H][Tf2N], [N444H][PF6], [C12mim][Cl], [C12mim][Tf2N] and [C12mim][PF6] for use in thermal energy storage. The thermal properties of these liquids have not been reported previously. The liquids were synthesized and characterized by nuclear magnetic resonance (NMR), elemental analysis (EA), and Fourier transform infrared spectroscopy (FTIR). Physical properties including density, speed of sound, and dynamic viscosity were measured at different temperatures. Thermal properties were determined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results showed that the ILs combined with the [Tf2N] anion had good thermal properties for use as heat transfer fluids (HTF), such as wide temperature ranges as liquids and high decomposition temperatures. The thermal storage densities of [C12mim][Tf2N] and [N444H][Tf2N] are 177 and 200MJm−3, respectively.