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[Display omitted] • The effecient DESs were screened for the separation of diethoxymethane and ethanol. • The key point of separating diethoxymethane and ethanol is identified. • The effect of DESs structure on LLE behavior was elucidated. • Microscopic mechanism on LLE behavior at the molecular level was revealed. The selection of efficient and environmental extractants is essential for the sustainable development of extraction processes. Based on the conductor-like screening model for the segment activity coefficient (COSMO-SAC), three deep eutectic solvents (DESs) were screened from 1000 DESs for the separation of diethoxymethane (DEM) and ethanol (EA). Subsequently, the liquid–liquid equilibrium behavior of the DEM + EA + DES system at different temperatures was measured. The results show that benzyltrimethylammonium chloride/glycerol (BTACl/GLY) has the highest selectivity and benzyltrimethylammonium chloride/ethylene glycol (BTACl/EG) and tetraethylammonium chloride/ethylene glycol (TEACl/EG) have similar extraction performance. More importantly, the extraction performance of DESs reported in this work is stronger than that of the solvents already reported. Additionally, analysis of the separation mechanism by various quantum chemical methods revealed that the purification of DEM and EA mixtures is mainly ascribed to the difference in electrostatic forces between the solvent and DEM/EA. The result confirmed that solvents with small molecular structures and strong nucleophilic sites are more competitive in separating the mixtures. [ABSTRACT FROM AUTHOR]

• The appropriate mixed solvent was selected for the desulphurization process. • Effect of the solvents on the LLE of thiophene/heptane was experimentally explored. • The relationship between LLE behaviors and microscopic interactions was unraveled. To meet the stringent requirements for sulfur content in gasoline, fuel oil desulfurization has become an indispensable process in petrochemical production. This study aimed to extract thiophene from heptane using a novel mixed solvent. In this work, the performance of single solvent N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and sulfolane (SULF) was investigated for the separation of thiophene and heptane at 298.15 K or 308.15 K, respectively. Ternary liquid-liquid equilibrium (LLE) data (heptane + thiophene + DMF, heptane + thiophene + DMSO and heptane + thiophene + SULF) shows that DMF has the highest distribution coefficient and DMSO has the highest selectivity. Subsequently, compared to a single solvent, the mixed solvent composed of the molar ratio of 1:7 tetrabutylammonium bromide-SULF (DES1) and DMSO has the highest selectivity and applicable distribution coefficient. The conclusion can be obtained from the quaternary LLE data (heptane + thiophene + DMF/DMSO, heptane + thiophene + DES1/DMSO and heptane + thiophene + DES1/DMF). And the NRTL and UNIQUAC models were used to correlate the LLE data. The mechanism of thiophene extraction from thiophene/heptane was elucidated by molecular dynamics (MD) simulations. The analysis of non-bonded interaction energies shows that the electrostatic force plays a major role in the separation of thiophene/heptane for the mixed solvent, and radial distribution functions demonstrates that the oxygen atom of DMSO, nitrogen atom atom of DMF and bromide ion of DES1 have strong interaction with hydrogen atom of thiophene. Therefore, this study provides theoretical guidance for the application of mixed solvents in the desulfurization of fuel oil process. [Display omitted] [ABSTRACT FROM AUTHOR]