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]

To develop a greener method to separate phenols from oils, four kinds of halogen-free zwitterions, including 1-(propyl-3-sulfonate)-triethylaminium (TEA-PS), 1-(propyl-3-sulfonate)-tripropylaminium (TPA-PS), 1-(butyl-4-sulfonate)-triethylaminium (TEA-BS) and 1-(butyl-4-sulfonate)-tripropylaminium (TPA-BS), were designed and synthesized to separate phenols from model oils via forming deep eutectic solvents (DESs) based on the formation of hydrogen bonding between OH group on phenol and the oxygen atom on SO 3 − group of the zwitterions. The effects of time, temperature, dosage of zwitterions, initial phenol content, and structure of zwitterions were investigated. The results show that the extraction process can reach equilibrium within 2 min and the extraction efficiency is not sensitive to temperature. The zwitterions separate well phenol from model oils at room temperature, and the minimum phenol contents follow the order: TEA-PS > TPA-PS > TEA-BS > TPA-BS. The minimum phenol content and the maximum extraction efficiency at 25 °C can reach 4.8 g dm −3 and 98.6%, respectively, by using TPA-BS. All the maximum extraction efficiency can be obtained with n zwitterions : n phenol of less than 0.4, which greatly reduces the dosages of extractants. Importantly, these zwitterions can avoid the introduction of halide ion, which can seriously corrode the process equipment. All these zwitterions can be easily regenerated by an anti-solvent method without an obvious mass loss and a decrease in phenol extraction efficiency. Lastly, the extraction mechanism was studied with FT-IR and the freezing points of DESs indicate that the DESs are formed through hydrogen bonding. [ABSTRACT FROM AUTHOR]

The separation of phenolic compounds from oil mixtures is widely used in the chemical industry. In this research, we found that two types of environmentally benign quaternary ammonium-based zwitterions, betaine and l -carnitine, could be used as new extractants for the separation of phenol from model oils by forming deep eutectic solvents (DESs). The effects of extraction time, temperature, mole ratio of zwitterion to phenol and initial phenol content on the efficiency of phenol separation were investigated. The results indicated that betaine and l -carnitine could form DESs with phenol, and the DESs were insoluble in model oils. Phenol in model oils could be extracted with extraction efficiencies up to 94.6% at an l -carnitine:phenol mole ratio of 0.4 (an l -carnitine:phenol mass ratio of 0.68) and 298.2 K. Phenol in DES could be recovered using an anti-solvent, and betaine and l -carnitine could be regenerated and reused for 4 cycles without obvious decreases in extraction efficiency and extractant mass, and they were not changed in their structures after reuse. The separation mechanism was investigated using FT-IR, which showed that betaine and l -carnitine formed DESs with phenol through hydrogen bonding. [ABSTRACT FROM AUTHOR]

[Display omitted] • The extraction performance of four green and low-cost ChCl-based DESs for phenol/toluene was investigated. • The effect of different glycols as HBDs on the separation was elucidated. • The intermolecular hydrogen bond interaction was analyzed by σ-profile based on COSMO-SAC model. • The extraction mechanism of DESs was revealed at molecular/atomic level. • Small molecular weight, short chain glycols as HBDs are more suitable for the separation process. Highly efficient separation of phenols from coal-to-liquids can enhance the economics of the coal conversion process. The selection of extractants with high extraction efficiency and low neutral oil entrainment is significant for energy development strategy. In this study, four ChCl-based DESs with different glycols as hydrogen bond donors (HBDs) were designed for the separation of phenol/toluene mixtures and the experimental results were analyzed by theoretical calculations. The experimental results showed that ChCl-EG had the highest extraction efficiency (94.02 %) and the least entrainment of toluene (0.449 g). Meanwhile, it could be regenerated and reused four times with no significant change in extraction capacity. The formation of hydrogen bonds between DESs and phenol was elucidated by σ-profile based on COSMO-SAC model. Multi-scale simulations and comparative analyses of the micro-mechanisms of the DESs system were carried out using quantum chemical (QC) and molecular dynamics (MD). It was shown that the attraction of DESs to phenol was mainly due to hydrogen bonds and vdW forces, with hydrogen bond interaction between Cl− in ChCl and H atom in phenol hydroxyl group being dominant. As the chain length of HBDs increased, the interaction of DESs with phenol was enhanced, while the entrainment of toluene also increased. Overall, the effect on the separation of phenol by different chain lengths of glycols as HBDs is elucidated. This study provides a theoretical reference for selecting and designing other DES extractants to separate phenol/toluene systems and similar systems. [ABSTRACT FROM AUTHOR]

Highlights • Phenolic compounds in oils are separated by biodegradable biological reagents (BRs). • The separation is based on Brønsted acid-Lewis base interaction. • The BRs show the highest phenol extraction efficiency of 99.1% at room temperature. • The BRs can be regenerated using anti-extraction method without loss in efficiency. • The BRs are of biodegradation, no halide ions and no pollution to the environment. Abstract Phenolic compounds, which are widely used in producing synthetic fibers, engineering plastics, and other industrial organic chemicals, can be obtained from oil mixtures before further processing or applications by separation. Based on Lewis/Brønsted acid-base theory, we proposed the separation of phenolic compounds from oil mixtures using some environmentally benign biological reagents (BRs, including 1,3-dimethylxanthine-DMX, isonicotinamide-INA, and L-lysine-LYS). The effects of stirring time, temperature, initial phenol concentration, and BR:phenol mole ratio on phenol removal were studied in detail. LYS, INA and DMX show phenol removal efficiencies of 98.4%, 82.2%, and 66.6% from toluene at BR:phenol mole ratios of 1.6, 1.4, and 0.4, respectively, and those of 99.1%, 91.8%, and 74.6% from n -hexane at BR:phenol mole ratios of 2.20, 1.60, and 0.80, respectively, at room temperature. The BRs were regenerated with an anti-extraction method for four cycles without significant changes in separation efficiency and their properties. In addition, it is found that there is little toluene entrained in the biological reagents, which is as low as 2.3 wt% of separated phenol, indicating high purities of products. These BRs show the advantages of easy biodegradation, no corrosion to the equipment and containers, and no pollution to the environment. [ABSTRACT FROM AUTHOR]

In this article, dicationic ionic liquids (DILs), including N , N , N , N ′, N ′, N ′-hexaethyl-ethane-1,2-diammonium dibromide (HEDBr), N , N , N , N ′, N ′, N ′-hexaethyl-propane-1,3-diammonium dibromide (HPDBr) and N , N , N , N ′, N ′, N ′-hexaethyl-butane-1,4-diammonium dibromide (HBDBr), were designed and used to extract phenolic compounds from model oil and coal tar oil. The effects of stirring time, temperature, DIL:phenol mole ratio, and initial phenol concentration on the extraction of phenol were studied. It is found that the DIL:phenol mole ratio is only around 0.3 when the highest extraction efficiency of phenol is obtained. The extraction process completes within 5 min at room temperature, and the extraction efficiency is not dependent on temperature. Also, the ultimate phenol concentration remains constant despite the difference in initial phenol concentrations. Of these DILs, HPDBr shows the lowest ultimate phenol concentration of 3.9 g/dm 3 , and the extraction efficiency of phenol can reach as high as 97.0%. These DILs can be regenerated by anti-solvent method and reused several times without significant reduction in extraction efficiency. In addition, HPDBr was demonstrated to extract phenolic compounds from real coal tar oil, and its extraction efficiency of phenolic compounds is 92.7%. The mechanism, analyzed by FT-IR, shows that there is a hydrogen bond between phenol and DIL. [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]