Molecular mechanism and process of efficient separation of tert-butanol and water azeotrope using tetraethylammonium chloride-based deep eutectic solvents

Tert-butanol (TBA) is a crucial solvent in the chemical and pharmaceutical industries. However, an azeotrope forms with water during its production process, making separation via traditional distillation methods challenging. This study employed the COSMO-Segment Activity Coefficient (COSMO-SAC) model to screen deep eutectic solvents (DESs) for the separation of the TBA-water azeotrope via extractive distillation (ED). Three DESs were selected and prepared: DES1 (tetraethylammonium chloride (TEAC): acetamide (1:2 M ratio)), DES2 (TEAC: ethylene glycol (EG) (1:2 M ratio)), and DES3 (TEAC: imidazole: EG (1:2:1 M ratio)). Vapor-liquid equilibrium (VLE) data for the TBA-water-DES systems were measured at 101.3 kPa. The results indicated that at 20 % (mole fraction) DES, all DESs disrupted the azeotrope, with DES3 proving the most effective. The Non-Random Two-Liquid (NRTL) model accurately fitted the experimental data. Quantum chemical analysis showed stronger interactions between the DES and water compared to TBA, leading to the disruption of the azeotrope. Process optimization of DES3-ED, using total annual cost (TAC) as the objective function, revealed significantly better economic performance compared to the conventional EG-ED process. © 2024 Elsevier B.V.