A combination of FTIR and DFT to study the microstructure properties of ionic liquid-acetonitrile-methanol systems.

Understanding the structural properties of ionic liquids (ILs) in azeotrope mixtures is crucial for designing and synthesizing IL entrainers tailored for extractive distillation. While extensive research has been conducted to comprehend the molecular properties of IL systems, much of this work has been limited to IL-cosolvent binary mixtures and fails to fully capture the essence of breaking azeotropy. In this study, we utilized Fourier-transform infrared spectroscopy (FTIR) and density functional theory (DFT) calculations to study the microstructure of the IL-azeotropic system. Leveraging the high resolution of excess spectroscopy and employing the methanol hydroxyl group as an effective probe, our research focused on the IL-acetonitrile-methanol mixtures. This approach enabled us to pinpoint species transformations during the mixing process, revealing the nature of phase equilibrium changes within the azeotrope. Consequently, our findings offer valuable insights into the microstructures of multicomponent solutions.