Search

Designing eco-friendly deep eutectic solvents (DESs) for industrial applications relies on choosing environmentally sustainable hydrogen bond acceptors (HBAs) and donors (HBDs). The study of the weak interactions between these components are essential to assess the performance of DESs in extraction and separation processes. However, there remains a dearth of knowledge regarding the molecular mechanisms influencing the structure-activity relationships in DES systems. This work introduces a new multiscale simulation analytical approach based on the mechanism revealed by the HBA-HBD interaction sites. Quantum chemical (QC) calculations were used to calculate the binding energy, weak interaction type and charge transfer analysis of each site. And the obtained microscopic mechanism was subsequently applied to a real macroscopic phenol-toluene separation system for cross-validation. Molecular dynamics (MD) simulations further illuminate the impact of HBA structure on the extraction process at the molecular level, corroborating QC calculation results. Notably, this underscores the significance of HBAs structure interactions with phenol. The multiple interaction sites of the L-carnitine structure with phenol validate the use of a lower L-carnitine dosage compared to ChCl and betaine in the liquid-liquid extraction (LLE) experiments. These results extend to advancing understanding of eco-friendly DESs, providing a basis for the development of sustainable and efficient extraction processes. [Display omitted] • Two natural, non-toxic compounds betaine and L-carnitine were chosen as HBAs. • The relationship between the structure of HBAs and their ability to segregate was elucidated by focusing on the interaction sites of HBAs with phenol. • QC calculations were used to compare the microscopic mechanisms of interaction between interaction sites in each system. • The microscopic mechanism was applied to the macroscopic system for cross-checking and mutual verification. [ABSTRACT FROM AUTHOR]

[Display omitted] • The roles of cresols played in DESs are clarified by experiments. • The binding interactions of DESs are revealed from theoretical perspectives. • The intermolecular interaction regions are visualized by reduced density gradient (RDG). • The energy decomposition analysis (EDA) confirms that the electrostatic effect is dominant. • The atoms in molecules analysis (AIM) describes the sites and types of weak interactions between DESs at the atomic level. To provide some guidance for the selective separation of cresol isomers from oils, the effect of structure on the physicochemical properties of deep eutectic solvents (DESs) formed by choline chloride (ChCl) and cresol isomers were studied. In this study, DESs with different mole ratios of cresols to ChCl (1.68 to 9.00) were prepared. The physicochemical properties (viscosity and density) of DESs, which were related to the separation process, were measured at different temperatures. The results indicated that the density and viscosity were closely related to the structure of cresols, temperature, and mole ratios of cresols to ChCl. Interestingly, when the mole ratio of cresols to ChCl was large enough, such as > 5.00, the density and viscosity got correspondingly closer to that of the pure cresols. This meant that cresols could not only serve as hydrogen bond donors to form DESs but also act as a solvent to dilute DESs. Finally, density functional theory (DFT) was used to reveal the microscopic properties and binding interactions of DESs. The most stable conformations, corresponding interaction energies and hydrogen bond length of DESs were obtained from the Gaussian 16 software, and Multiwfn 3.8 program was used to perform wave function analysis of the system. The results showed that the interaction between ChCl and cresol isomers decreased in the order o -cresol, m -cresol, and p -cresol, and the hydrogen bond dominated the interaction. The results at the molecular/atomic level further verified the experiment results, and a better understanding of the structural characteristics and intermolecular interactions of DESs could provide opportunities for the application of DESs. [ABSTRACT FROM AUTHOR]

Indole plays a significant role in the production of products such as spices, medicines, and exogenous auxins. Deep eutectic solvents (DESs) formed by indole and quaternary ammonium salts (QASs, including tetraethylammonium chloride-TEAC, tetrapropylammonium chloride-TPAC, triethylmethyl-ammonium chloride-TEMAC) were found and proposed to efficiently extract indole from model wash oil. The effects of time, temperature, mole ratio of QAS to indole and initial indole concentration on the extraction of indole were studied. The results indicate that these QASs can extract indole from wash oil with efficiencies up to 96.7% (TPAC). The extraction process can be finished within 5 min. It is also found that the ultimate concentrations are almost identical for one kind of QAS although their initial concentrations are different, and the indole concentration in model wash oil can be reduced to a very low level of 1.3 g/dm 3 (TPAC). The maximum distribution coefficients of indole are 40.8 for TEAC, 91.9 for TPAC, and 29.5 for TEMAC at the studied conditions, and the extraction ability follows the order of TPAC > TEAC > TEMAC. Moreover, QASs in DESs can be reused without obvious reduction in extraction efficiency. The extraction mechanism was studied by FT-IR, and the results indicate that there is a hydrogen bond between QAS and indole. Finally, a comparison was made between this method and other methods to verify and demonstrate its desirable properties of efficiency and environmentally friendliness. [ABSTRACT FROM AUTHOR]

Forming deep eutectic solvents (DESs) by quaternary ammonium salts (QASs) and phenolic compounds to extract phenolic compounds from oil mixtures is effective. However, a small amount of neutral oil is entrained in the DESs. In this work, we proposed an anti-extraction method to remove the neutral oil entrained in DESs. Low-carbon alkanes (LCAs, including n -hexane, cyclohexane, and n -nonane) were added to model DESs to remove neutral oil. We found that the LCAs could effectively remove neutral oil entrained in the DESs. Of the three LCAs, n -hexane showed the best performance, and the removal rate of neutral oil could reach as high as 92.2%. The separation process could complete within 15 min, and the removal rate of neutral oil did not change significantly with temperature. In addition, n -hexane could effectively remove neutral oils in DESs formed by real coal tar and choline chloride. The neutral oil content in the phenolic compound product decreased to only 1.9 wt%, which greatly improves the purity of the phenolic compound product. [ABSTRACT FROM AUTHOR]

Phenolic compounds (such as phenol, cresol sand xylenol), which are basic materials for the organic chemical industry, are mainly produced from coal liquefaction oil, coal tar, petroleum, and biomass pyrolysis oil. It has been reported that the separation of phenols from oil with forming deep eutectic solvents based on quaternary ammonium salt (QAS) is an efficient and environmentally friendly method. However, the phase equilibrium of QAS + phenol + oil mixtures has not been reported in the literature. In this work, the phase equilibrium for separating phenol from model oil with 2-hydroxy- N , N , N -trimethyl-ethanaminium chloride (ChCl), N , N , N -triethyl-ethanaminium chloride (TEAC), and N , N , N -trimethyl- methanaminium chloride (TMAC) was studied. Phase equilibria of three ternary systems of toluene + phenol + QAS were measured at 25.0, 40.0 and 65.0 °C, and phase behaviors of the ternary systems were studied. Effects of temperature, type and dosage of QAS on the equilibrium were investigated. The results show that low temperatures are beneficial to extraction of phenol and the phenol removal efficiency decreases with increasing temperature. Among the QASs, TEAC has the strongest ability to separate phenol, but the concentration of toluene entrained in the DES phase is the largest. Only TMAC is dissolved in the oil phase to a small extant, which can cause the loss of extractant. ChCl not only has high phenol removal efficiency, but also causes a small concentration of toluene entrained in the DES phase, which shows that ChCl is an efficient and environmentally friendly extractant. [ABSTRACT FROM AUTHOR]

Phase equilibria of the binary systems of high pressure CO 2 + deep eutectic solvents (DESs) formed by quaternary ammonium salts (QASs, including 2-hydroxy- N , N , N -trimethyl-ethanaminium chloride, ChCl; N , N , N -trimethyl-methanaminium chloride, TMAC; and N , N , N -triethyl-ethanaminium chloride, TEAC) and phenol were measured at temperatures from 313.15 K to 333.15 K, pressures from 1.71 MPa to 13.3 MPa and mole ratios of phenol to QAS from 2.00 to 4.00. It has been found that two-phase equilibrium exists at all the studied conditions. The solubility of phenol in the CO 2 phase and the solubility of CO 2 in the DES phase at different pressures, temperatures, mole ratios of phenol to QAS have been obtained. Both the solubility of phenol in the CO 2 phase and the solubility of CO 2 in the DES phase formed by ChCl and phenol shows the largest, while those in the DES phase formed by TEAC and phenol shows the smallest. This work provides phase equilibrium data for phenol extraction and QAS regeneration. [ABSTRACT FROM AUTHOR]