Choline Chloride-based Deep Eutectic Solvents Research Articles

Entropy scaled viscosities of choline-chloride-based deep eutectic solvents using a cubic EoS with volume translation

The present modeling work formally introduces, for the very first time, the application of the residual-entropy scaling approach to adequately represent the dynamic viscosity of deep eutectic solvents (DESs) as a function of temperature and density. In doing so, diverse unreduced and reduced viscosity forms (total viscosity, Rosenfeld and dilute gas) were verified and compared. The use of a cubic equation of state (CEoS: Soave-Redlich-Kwong or Peng-Robinson) served here to provide sufficiently accurate residual entropy data required by the present scaling procedure. Experimental DES density data were also modeled by applying a modified Mathias volume translation to the density data originally obtained from the two CEoS during the present scalings. The resulting modeling approach was sucessfully validated during the representation of experimental dynamic viscosities and mass densities of three of the most representative choline chloride-based DESs: ChCl:Urea(1:2), ChCl:Ethylene Glycol(1:2) and ChCl:Glycerol(1:2) within a temperature range varying from 10 to 100 °C and at pressures from 1 to 1,000 bar.

Celecoxib solubility in two choline chloride-based deep eutectic solvents- Experimental study, thermodynamic modeling, and molecular dynamic simulation

In the present study, we investigated the solubility of celecoxib the in the aqueous solution of two deep eutectic solvents (DESs) at various DES weight fractions within the temperature range of 283.2-323.2 K. Choline chloride (ChCl) as hydrogen bond acceptor (HBA) and ethylene glycol (EG) and 1,2-propanediol (PD) as hydrogen bond donors (HBDs) were used for the preparation of DESs. Experimental results showed that the solubility of celecoxib is significantly enhanced by approximately one million times in DES-contained PD compared to pure water. Also, celecoxib's solubility was enhanced by increasing temperature and the weight fraction of DESs. Besides, DES2 (ChCl + PD) showed a higher solubility for celecoxib compared to DES1 (ChCl + EG) in all experiments. Moreover, two temperature-dependent Buchowski-Ksiazaczak λh and modified Apelblat equations and the local composition models such as Wilson, non-random two-liquid theory (NRTL), and universal quasi-chemical (UNIQUAC) were applied to correlate the experimental solubility data. The correlated solubility was in good agreement with the experimental data. In addition, two-segment-based models, including non-random two-liquid-segment activity coefficient (NRTL-SAC) and universal quasi-chemical segment activity coefficient (UNIQUAC-SAC) models provided relatively good performance in solubility prediction. Furthermore, the calculation of the apparent standard thermodynamic properties showed that enthalpy is the primary contribution term to the apparent standard Gibbs free energy in the dissolution process of celecoxib. Finally, we applied molecular dynamics simulations to describe the drug solubility from the molecular point of view. The radial distribution function (RDF) analysis revealed that the experimental solubility is consistent with the MD simulation results, so the attractive interactions between celecoxib-DES1 and celecoxib-DES2 are much higher than the water-celecoxib.

Molecular design and experimental study of deep eutectic solvent extraction of keratin derived from feathers

Feather keratin has a complex structure, hard texture and must be treated to improve its bioavailability. In this paper, according to the designability of DES, some deep eutectic solvents (DESs) were prepared to degrade feathers and extract keratin. Calculations by quantum chemical methods showed that DESs were considered molecular scissors with the ability to break initial hydrogen bonds and form new bonds only when the Gibbs free energy change for the degradation process was ΔG < 0, i.e., hydrogen binding energy ΔE < −0.3038 kcal/mol. Then, the degradation mechanism was predicted to provide guidance for the molecular design of DES. Finally, experimental results showed that the same ratio of choline chloride-based DESs had higher catalytic performance, in which [ChCl][P][ZnCl2] 1:5:2 was used with a high yield of keratin of 85.46 %. DES had a high catalytic performance after multiple recycling cycles and this method has no H2S gas generation, which improves the atomic utilization.

Quantum chemical investigation of choline chloride-based deep eutectic solvents

The current quantum-based research focuses on the eutectic mixtures formulated by combining hydrogen bond donors (malic acid, tartaric acid, oxalic acid, ethylene glycol, and glycerol) and acceptor (choline chloride) molecules. Choline chloride (ChCl) is used as a hydrogen bond acceptor (HBA) having specified mole ratios with hydrogen bond donors (HBDs) to develop five deep eutectic solvents (DESs). Density functional theory (DFT) is used to examine the molecular dynamics (MD) of DESs to interpret the method's validity and quantum chemical aspects. The resemblance of the experimental Fourier-transform-infrared (FT-IR) vibrational frequencies with the calculated vibrational frequencies validates the Becke, 3-parameter, Lee–Yang–Parr (B3LYP) functional with basis set 6-31G. The frontier molecular orbitals (FMOs) and quantum chemical investigation reveal that among five solvents, DES1 (ChCl: EG) is the best solvent with the lowest energy gap (0.02 eV), highest chemical potential (0.19 eV), chemical softness (42.73 eV), and electrophilicity index (1.55 eV) and with least chemical hardness (0.01 eV) and electronegativity (−0.19 eV). This quantum acumen provides an effective revelation to design the required conductive solvents based on the DFT study. The density of states (DOS) provides insight that how many states were occupied in the unit of energy and can be used to evaluate the electronic structure. DFT-B3LYP/6-31G is used to simulate vibrational and quantum features of the experimentally prepared DESs.

A Novel Ascorbic Acid Based Natural Deep Eutectic Solvent as a Drilling Mud Additive for Shale Stabilization

During drilling, almost 70% of wellbore instability issues result from the encountering of shale formations. Various additives such as salts, silicates, and polymers are used in water-based mud to enhance its shale-inhibition capability; however, such additives have certain limitations. Lately, ionic liquids and deep eutectic solvents (DES) have been used by various research groups as shale inhibitors in drilling fluid due to their biodegradability and efficacy. However, their popularity faded when a natural derivative of DES, i.e., Natural Deep Eutectic solvent (NADES), came into the picture. This research utilizes the in-house-prepared Ascorbic acid and Glycerine (AA:Gly)-based NADES as a drilling fluid additive for shale inhibition and compares its efficacy with counterpart inhibitors such as KCl, imidazolium-based ionic liquid, and Choline Chloride-based DES. The results show that 3% NADES improved the overall Yield point to Plastic viscosity ratio, with a 39.69% decline in mud cake thickness and a 28% decline in the filtrate volume of drilling mud. Along with improved drilling fluid properties, 3% NADES resulted in 77.77% shale inhibition and 87% shale recovery. Surface tension, d-spacing, zeta potential, and FESEM have been conducted to justify and elucidate the inherent mechanism behind the working of NADES as a drilling fluid additive and clay stabilizer. Thus, Ascorbic acid-based NADES is recommended as a potential non-toxic and cheap drilling fluid additive to improve drilling fluid properties and clay stability.

Separation of methanol and ethanol from azeotropic MTBE mixtures using choline chloride-based deep eutectic solvents

In this study, the performance of five different choline chloride – based deep eutectic solvents (DESs), including ChCl – urea, ChCl – ethylene glycol, ChCl – glycerol, ChCl – 1,2- propanediol, and ChCl – glucose, has been experimentally and computationally investigated for the purpose of liquid – liquid extraction at 298.15 K and 1 atm. In this regard, the effect of them on the extraction efficiency to separate methanol and ethanol from azeotropic systems, methyl tert-butyl ether (MTBE) + ethanol and MTBE + methanol, is studied. To synthesize these DESs, chlorine chloride as a hydrogen bond acceptor (HBA) is blended with urea, ethylene glycol, glycerol, 1,2- propanediol, and glucose as hydrogen bond donors (HBDs). Through the investigation, it is revealed that all the studied DESs deliver a distribution coefficient, β, that is higher than unity (β > 1). Similarly, the measured selectivities for these DESs have presented values that are far greater than unity (S ≫ 1). This is advantageous as it demonstrates their industrial applications. Furthermore, to have a better view of how effective they are in terms of the extraction capacity, the experimental data have been compared to the performance of ionic liquids used for the liquid – liquid extraction of MTBE + methanol. The reliability of the tie-line compositions was checked by applying the Othmer–Tobias equation. Additionally, to show the consistency, UNIQUAC Functional-group Activity Coefficients (UNIFAC) as a thermodynamic model has been employed to predict the equilibrium tie-lines. The predicted data is compared with the experimentally measured data through the calculation of the root-mean-square deviation (RMSD), showing that both predicted and experimental data are in a good agreement together.

Biodiesel production through electrolysis in the presence of choline chloride-based deep eutectic solvent: Optimization by response surface methodology

In this study, a novel catalyst-free electrolysis method was developed that uses deep eutectic solvents (DESs) as both a supporting electrolyte and a cosolvent for biodiesel synthesis. Various choline chloride–based DESs for biodiesel production were prepared and tested. Among the DESs that were synthesized, DES-2 (choline-chloride-to-ethylene-glycol molar ratio of 1:2) exhibited the highest efficiency for electrolysis-based biodiesel synthesis. The DES-2-assisted electrolysis was then optimized through the application of a response surface methodology to maximize biodiesel yield. The maximal biodiesel yield of 94.71 % was obtained through electrolysis when an electrolysis voltage of 22.06 V, a DES concentration of 7.91 % (w/w), a water amount of 1.44 % (w/w), a methanol-to-oil molar ratio of 25.09:1, and a reaction time of 2 h were applied at room temperature. Notably, DES-2 could be reused for four cycles to achieve a biodiesel yield of > 80 % biodiesel. The properties of the synthesized biodiesel were verified as meeting international standards. This study suggests that electrolysis involving the use of DESs as a supporting electrolyte and a cosolvent is an eco-friendly, cost-effective, and efficient method for biodiesel synthesis.

Influence of water on the conformations and interactions within two choline chloride-based deep eutectic solvents: a density functional theory investigation

Influence of water on the conformations and interactions within two choline chloride-based deep eutectic solvents: a density functional theory investigation

Chitins from Seafood Waste as Sustainable Porous Carbon Precursors for the Development of Eco-Friendly Supercapacitors

Carbon materials derived from marine waste have been drawing attention for supercapacitor applications. In this work, chitins from squid and prawn marine wastes were used as carbon precursors for further application as electrodes for energy storage devices. Chitins were obtained through a deproteinization method based on enzymatic hydrolysis as an alternative to chemical hydrolysis as commonly presented in the literature. The obtained porous carbons were characterized using a BET surface area analyzer to determine the specific surface area and pore size, as well as scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), Raman spectroscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), to characterize their morphology, composition, and structure. The electrochemical characterization was performed using a glassy carbon (GC) electrode modified with marine waste-based porous carbons as the working electrode through cyclic voltammetry and galvanostatic charge/discharge using ethaline, a choline chloride-based deep eutectic solvent (DES), as an eco-friendly and sustainable electrolyte. Squid and prawn chitin-based carbons presented a surface area of 149.3 m2 g-1 and 85.0 m2 g-1, pore volume of 0.053 cm3 g-1 and 0.029 cm3 g-1, and an associated specific capacitance of 20 and 15 F g-1 at 1 A g-1, respectively. Preliminary studies were performed to understand the effect of -OH groups on the chitin-based carbon surface with DES as an electrolyte, as well as the effect of aqueous electrolytes (1 mol L-1 sulphuric acid (H2SO4) and 1 mol L-1 potassium hydroxide (KOH)) on the capacitance and retention of the half-cell set up. It is provided, for the first time, the use of chitin-based carbon materials obtained through a one-step carbonization process combined with an eco-friendly DES electrolyte for potential application in energy storage devices.

Efficient and eco-friendly isolation and purification of lignin from black liquor with choline chloride-based deep eutectic solvents

Abstract This study developed an efficient and green method for isolating and purifying lignin from black liquor (BL) using deep eutectic solvents (DESs). After the short and mild process (700 W microwave-assisted, 100 °C, DES: BL 1:5 (v: v), 30 min) using optimized DES (lactic acid (LA): choline chloride (ChCl) 10:1, molar ratio), the yield and purity of lignin obtained from 100 mL BL was 1.58 g and 88.12%, respectively, which was more efficient than the results of 1.18 g and 78.54% of the conventional process. Furthermore, more than 95% of initial results were obtained after three cycles. The composition and structure of DESs and conventionally purified lignin were slightly different. The solvent costs for both processes were also evaluated, showing that the DES process has great potential to replace traditional bulky and environmentally unfriendly procedures for lignin isolation and purification and to help develop new strategies for the potential added value of lignin.

Chemometric study for the performances of deep eutectic solvents during the recovery of high-added-value substances from Moringa oleifera leaves: Principal component analysis.

Moringa oleifera is a plant with high antioxidant content in its leaves, flowers and seeds. It attracts the attention of researchers with the effect of its nutritional and medical advantages. The purpose of the current study is to propose a deep eutectic solvent (DES)-based ultrasound-assisted extraction of bioactive substances from M. oleifera leaves by the application of a chemometric study. A total of 18 different choline chloride-based DESs were prepared by using several hydrogen bond donors (glucose, sucrose, glycerol, ethylene glycol, urea and dimethyl urea) with various molar ratios (1:1, 1:2 and 2:1) by addition of diluents (water and 50% methanol) or alone. In order to decide the best DES combination, principal component analysis (PCA) was applied. The response surface method (RSM) was used as statistical experimental design approach through the Box-Behnken design. The best phenolic (TPC), flavonoid (TFC) and antioxidant activity yields of M. oleifera leaf extract were found to be 19.102 mg-GAE, 10.47 mg-CE and 24.404 mg-TEAC per gram dried leaf under the optimal conditions (50% water content, 20% amplitude, 15 min time). The model fitting has been also found reliable depending on the statistical indicators such as p-value (<0.0001), coefficients of determination (R2 = 0.9827, 0.9916 and 0.9864) and root mean square error (RMSE = 1.0562, 2.4656 and 0.7713). A chemometric study through PCA was carried out to determine the similarities and differences between the solvent groups, and the ethylene glycol-based DES (1:2, molar ratio) with the addition of water showed the best performance.

Effects of deep eutectic solvents on the biotransformation efficiency of ω-transaminase

ω-transaminase (ω-TA) shows a significant promising in the synthesis of chiral amines. However, the poor activity of ω-TA in buffer water solution limits its application in industry, so green and economic methods adopted to improve ω-TA activity still face challenges. Here, deep eutectic solvents (DES) were used as the co-solvent to improve the catalytic activity of ω-TA. The results have shown that DES (ChCl: Urea 1:1) was the most suitable co-solvent for increasing the biotransformation efficiency of the ω-TA in nine different choline chloride-based DESs. The optimal enzymatic activity was achieved at 40 ℃, in 10 vol% DES and pH 8. The specific activity of ω-TA in DES was increased by 3.9 times due to the reinforced interactions between DES and enzyme. The kinetic analysis of transaminase showed that DES enhanced affinity of ω-TA for 1-(R)-PEA and pyruvate to increase by 1.93 and 1.63 times respectively compared with the control. Molecular docking shows that urea acted as a proton donor and a receptor during the enzymatic reaction, the docking binding energy increases to 3.21 and 3.59 kcal/mol, promoting the transamination reaction. DES can significantly improve the catalytic activity of ω-TA, which has broad development prospects in the field of green and efficient synthesis of pharmaceutical and natural product intermediates.

Enhancing effect of choline chloride-based deep eutectic solvents with polyols on the aqueous solubility of curcumin–insight from experiment and theoretical calculation

The development of green solvents for enhancing aqueous solubility of drug curcumin remains a challenge. This study explores the enhancing effect of deep eutectic solvents (DESs) on the aqueous solubility of curcumin (CUR) via experiment and theoretical calculation. Choline chloride-based DESs with polyols 1,2-propanediol (1,2-PDO), 1,3-propanediol, ethylene glycol, and glycerol as hydrogen bond donors were prepared and used as co-solvents. The CUR aqueous solubility increased with increasing the DESs content at temperature of 303.15–318.15 K, especially in aqueous ChCl/1,2-PDO (mole ratio 1:4) solutions. The positive apparent molar volume values and reduced density gradient analysis confirmed the existence of strong interactions between CUR and solvent. The van der Waals interactions and hydrogen bonding coexisted in DESs monomer retained the stability of DESs structure after introducing CUR. Moreover, the lower interaction energy of DESs⋅⋅⋅CUR system than that of the counterpart DESs further proved the strong interaction between CUR and DESs. The lowest interaction energy of ChCl/1,2-PDO⋅⋅⋅CUR system indicated that this system was the most stable and ChCl/1,2-PDO was promising for CUR dissolution. This work provides efficient solvents for utilizing curcumin, contributing to a deep insight into the interactions between DES and CUR at the molecular level, and the role of DESs on enhancing drugs solubility.

Direct conversion of chitin derived N-acetyl-D-glucosamine into 3-acetamido-5-acetylfuran in deep eutectic solvents

3-Acetylamino-5-acetylfuran (3A5AF) is an important nitrogen-containing fine chemical with broad application prospects and high research value. Herein, we report a novel method for the conversion of N-acetyl-d-glucosamine (NAG) to 3A5AF in the choline chloride-based deep eutectic solvents (DESs). The catalytic activities of various DESs have been smoothly screened, and DES 2 (choline chloride/PEG-200/boronic acid = 1/1/0.5) displayed the best catalytic performance. In the absence of any additional solvent, catalyst and additive, product 3A5AF was obtained in 18.3% yield after reacting at 180 °C for 15 min under atmospheric condition. In addition, DES 2 showed a good reusability. The possible reaction pathway was elucidated on the basis of the results of LC-MS and 13C NMR spectra. This study provided a new perspective for the application of DES in the conversion of chitin biomass.

Effect of choline chloride-based deep eutectic solvents on polyphenols extraction from cocoa (Theobroma cacao L.) bean shells and antioxidant activity of extracts

The effective extraction of natural compounds from cocoa bean shells using deep eutectic solvents could contribute to the sustainable valorization of this waste material. The objective of this study was to: (1) analyze the extraction kinetics of polyphenols released from cocoa (Theobroma cacao L.) bean shells (CBS) by the solid-liquid extraction method using choline chloride-based deep eutectic solvents (ChCl-DES) and their aqueous solutions; (2) investigate the effect of choline chloride-based deep eutectic solvents (ChCl-DES) aqueous solutions on in-vitro antioxidant capacity and the main individual compounds of the extracts. ChCl-DES were prepared with lactic acid, glycerol, and ethylene glycol in a 1:2 ratio. Aqueous solutions (30%, 40%, and 50% water) to obtain solvents with different physicochemical properties were performed. The total phenolic content (TPC) was determined by the Folin-Ciocalteu method. The solution of Fick's law model for plate geometry particles was applied to fit the experimental data and calculate the effective diffusivity coefficient (De). The antioxidant capacity of the extracts was analyzed by a combination of 2,2-diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl (DPPH) free radical scavenging capacity and ferric-reducing antioxidant power (FRAP) assays. The main bioactive compounds were quantified by high-performance liquid chromatography. The results showed that the type of hydrogen bond donor influences the total phenolic content, antioxidant activity and the main individual compounds in the extracts. Moreover, the washing/diffusion mechanism adequately depicts the extraction kinetics data for total phenolic content. However, the influence of an additional mechanism that enhanced the extraction capacity of deep eutectic solvents compared with organic solvent was confirmed.

Efficacy of modified carbon molecular sieve with iron oxides or choline chloride-based deep eutectic solvent for the separation of CO2/CH4.

It is necessary to separate CO2 from biogas to improve its quality for the production of biomethane. Herein, an improvement in the separation of CO2/CH4via adsorption was achieved by modifying the surface of CMS. The surface modification of CMS was performed by impregnation with metal oxide (Fe3O4) and N-doping (DES-[ChCl:Gly]). Subsequently, the efficacy of the surface-modified CMS was investigated. This involved CMS modification, material characterization, and performance analysis. The uptake of CO2 by CMS-DES-[ChCl:Gly] and CMS-Fe3O4 was comparable; however, their performance for the separation of CO2/CH4 was different. Consequently, CMS-DES-[ChCl:Gly] and CMS-Fe3O4 exhibited ca. 1.6 times enhanced CO2 uptake capacity and ca. 1.70 times and 1.55 times enhanced CO2/CH4 separation, respectively. Also, both materials exhibited similar repeatability. However, CMS-DES-[ChCl:Gly] was more difficult to regenerate than CMS-Fe3O4, which is due to the higher adsorption heat value of the former (59.5 kJ).

Amine protection by in situ formation of choline chloride-based deep eutectic solvents

Protection of amine groups by amide formation is still among the preferred strategies for multifunctional molecular synthesis despite its waste production, especially the enormous quantities of organic solvents used.

Comparison of the Degradation Performance of Seven Different Choline Chloride-Based DES Systems on Alkaline Lignin.

Lignin is a natural polymer second only to cellulose in natural reserves, whose structure is an aromatic macromolecule composed of benzene propane monomers connected by chemical bonds such as carbon-carbon bonds and ether bonds. Degradation is one of the ways to achieve the high-value conversion of lignin, among which the heating degradation of lignin by deep eutectic solvent (DES) can be an excellent green degradation method. In this study, choline chloride (CC) was used as the hydrogen bond acceptor, and urea (UR), ethylene glycol (GC), glycerol (GE), acetic acid (AA), formic and acetic mixed acid (MA), oxalic acid (OX), and p-toluenesulfonic acid (TA) were used as hydrogen bond donors to degrade lignin. NMR hydrogen spectroscopy was used for the simple and rapid determination of phenolic hydroxyl groups in lignin. FT-IR spectroscopy was used to characterize the changes of functional groups of lignin during DES treatment. GPC observed the molecular weight of lignin after degradation and found a significant increase in the homogeneity (1.6-2.0) and a significant decrease in the molecular weight Mw (2478-4330) of the regenerated lignin. It was found that acidic DES was more effective in depolymerizing alkaline lignin, especially for the toluene-choline chloride. Seven DES solutions were recovered, and it was found that the recovery of DES still reached more than 80% at the first recovery.

N2,N6-Bis(6-iodo-2-methyl-4-oxoquinazolin-3(4H)-yl)pyridine-2,6-dicarboxamide

A green chemistry method was applied in the synthesis of N2,N6-bis(6-iodo-2-methyl-4-oxoquinazolin-3(4H)-yl)pyridine-2,6-dicarboxamide. The desired compound was synthesized mechanochemically, using a choline chloride-based deep eutectic solvent as a catalyst. The synthesis took 20 min and the new compound was characterized using different spectral methods.

MD simulations explain the excess molar enthalpies in pseudo-binary mixtures of a choline chloride-based deep eutectic solvent with water or methanol.

The addition of molecular liquid cosolvents to choline chloride (ChCl)-based deep eutectic solvents (DESs) is increasingly investigated for reducing the inherently high bulk viscosities of the latter, which represent a major obstacle for potential industrial applications. The molar enthalpy of mixing, often referred to as excess molar enthalpy H E-a property reflecting changes in intermolecular interactions upon mixing-of the well-known ChCl/ethylene glycol (1:2 molar ratio) DES mixed with either water or methanol was recently found to be of opposite sign at 308.15K: Mixing of the DES with water is strongly exothermic, while methanol mixtures are endothermic over the entire mixture composition range. Knowledge of molecular-level liquid structural changes in the DES following cosolvent addition is expected to be important when selecting such "pseudo-binary" mixtures for specific applications, e.g., solvents. With the aim of understanding the reason for the different behavior of selected DES/water or methanol mixtures, we performed classical MD computer simulations to study the changes in intermolecular interactions thought to be responsible for the observed H E sign difference. Excess molar enthalpies computed from our simulations reproduce, for the first time, the experimental sign difference and composition dependence of the property. We performed a structural analysis of simulation configurations, revealing an intriguing difference in the interaction modes of the two cosolvents with the DES chloride anion: water molecules insert between neighboring chloride anions, forming ionic hydrogen-bonded bridges that draw the anions closer, whereas dilution of the DES with methanol results in increased interionic separation. Moreover, the simulated DES/water mixtures were found to contain extended hydrogen-bonded structures containing water-bridged chloride pair arrangements, the presence of which may have important implications for solvent applications.