Leveraging Imidazolium/Pyrrolidinium [Dicyanamide] Ionic Liquids to Enhance the Low-Temperature Behavior of γ-Butyrolactone

Leveraging ionic liquids (ILs) to enhance the performance of common solvents is a promising and efficient approach to engineer novel working fluids that can aid in addressing unique industrial processing needs. Here, we demonstrate enhanced solvent behavior by addition of IL, which, among other things, results in a significantly expanded liquidus range and low viscosity at temperatures below the crystallization point of the sole solvent. Specifically, we demonstrate that the low-temperature behavior of an organic solvent, γ-butyrolactone (GBL), can be significantly enhanced through the addition of an ionic liquid 1-ethyl-3-methylimidazolium (EMIM) or 1-butyl-3-methylimidazolium (BMIM) or 1-butyl-1-methyl pyrrolidinium (BMPyrr), paired with a common counterion, dicyanamide (DCA). A systematic series of experimental characterizations are used to explore three ionic liquids with superior liquidity at room temperature. We demonstrate the significance of cation selection for low-temperature system performance with respect to phase behavior, viscosity, and specific heat capacity, with a particular emphasis on sub 0 °C temperatures. The work has a significant impact on the development and understanding of low-temperature working fluids, whose physiochemical nature and stability at low temperatures determine both practicability and efficiency in industrial applications.