Desulfurization of Model Oil Using Green Solvents: Extractive Separation of Thiophene and Benzothiophene from <i>n</i> -Hexane and Thermodynamic Modeling Using Classical <i>G</i> ^E Models and COSMO-SAC

High Resolution Image Download MS PowerPoint Slide This study evaluates the extractive desulfurization of model oil using three green solvents: dihydrolevoglucosenone (DLG), γ-valerolactone (GVL), and dimethyl isosorbide (DMI). Liquid–liquid equilibrium (LLE) was experimentally determined for ternary systems consisting of n -hexane + thiophene/benzothiophene + green solvent at 298.15 and 308.15 K. To provide a robust thermodynamic foundation, binary LLE for the n -hexane + GVL system was measured across the full composition range, filling a significant gap in existing literature. These data were modeled using NRTL and UNIQUAC equations, while the extended-scaling law (ESL) equation was used to describe the critical region. The ternary LLE data reveal that DLG and GVL are highly effective desulfurization agents, demonstrating distribution coefficients and selectivity comparable to conventional hazardous solvents and ionic liquids. Ternary LLE data were successfully described using the NRTL model. Additionally, the quantum-mechanics-based COSMO-SAC model was employed for predictive analysis. Notably, COSMO-SAC provided encouraging quantitative agreement for DLG-based systems. These findings highlight the potential of DLG and GVL as high-performance, green components for industrial fuel purification processes.