This study investigates the solubility of triethylamine hydrochloride (TEA·HCl) in acetonitrile (ACN) and dimethyl carbonate (DMC) mixtures, crucial for optimizing TEA·HCl separation during vinylene carbonate (VC) synthesis. Solubility was measured experimentally at 0.1 MPa from 308.15 K to 343.15 K across ACN mass fractions ( \({w}_{1}\) ) from 0.1 to 1.0. Results reveal a positive correlation between TEA·HCl solubility, temperature, and \({w}_{1}\) . The Jouyban–Acree, Van’t Hoff–Jouyban–Acree, and Apelblat–Jouyban–Acree models were employed to correlate the solubility data. While generally accurate (average ARD ≈ 8.3%), these models exhibited substantial errors at \({w}_{1}\) = 0.1 (ARD > 40%). Thermodynamic analysis revealed an endothermic, enthalpy-driven dissolution process. Density Functional Theory (DFT) calculations identified a sharp change in solvation free energy at \({w}_{1}\) = 0.1, correlating with the observed solubility deviations and model inaccuracies. This study provides essential solubility data and thermodynamic insights for enhancing TEA·HCl crystallization and separation during VC production, emphasizing the critical role of solvent composition.
