Deep Eutectic Solvent System Research Articles

Production of Xylitol and Ethanol from Agricultural Wastes and Biotransformation of Phenylacetylcarbinol in Deep Eutectic Solvent

Converting agricultural biomass wastes into bio-chemicals can significantly decrease greenhouse gas emissions and foster global initiatives towards mitigating climate change. This study examined the co-production of xylitol and ethanol from xylose and glucose-rich hydrolysates of corn cob (CC), sugarcane bagasse (SCB), and rice straw (RS) without prior detoxification, using C. magnoliae (C. mag), C. tropicalis (C. trop), and C. guilliermondii (C. guil). A score ranking system based on weighted yields and productivity assessed the best raw material and yeast strain combination. The study revealed that C. mag cultivated on RS hemicellulosic and CC cellulosic media exhibited statistically significant (p ≤ 0.05) superiority in xylitol (272 ± 5) and ethanol 273 ± 3, production. The single-phase emulsion system using frozen-thawed whole cells of CC—C. mag, CC—C. trop, and RS—C. guil was utilized for phenylacetylcarbinol (PAC) biotransformation. Although similar PAC concentration within 14.4–14.7 mM was obtained, the statistically significant higher (p ≤ 0.05) volumetric pyruvate decarboxylase (PDC) activity from C. mag at 360 min was observed by 28.3 ± 1.51%. Consequently, further utilization of CC—C. mag in a two-phase emulsion system (Pi buffer: vegetable oil (Vg. oil) and Pi buffer: deep eutectic solvents (DES)) revealed that Pi buffer: DES medium preserved volumetric PDC activity (54.0 ± 1.2%) statistically significant higher (p ≤ 0.05) than the Pi buffer: Vg. oil system (34.3 ± 1.3%), with no statistically significant difference (p > 0.05) in [PAC]. These findings outlined the sustainable pioneering approach for the co-production of chemicals and reusing the residual yeast cells for PAC biotransformation in the Pi buffer: DES system.

Ligand‐Free Zn Catalyzed Synthesis of Functionalized iIdoloacridines

Abstract: An efficient, ligand‐free, and Zn‐catalyzed dehydrogenation of acridinol/ cyclization of imine product/ dehydrogenative C(sp3)‐H functionalization utilizing ChCl‐based deep eutectic solvent system for the assembly of functionalized indoloacridines 9 is reported. The protocol features mild reaction conditions, VOCs free process, broad substrate scope, and applicable gram‐scale synthesis. Furthermore, absorption and solvatochromism properties were explored for the synthesized compounds.

The preparation and properties of bamboo lignocellulosic nanofibers based on deep eutectic solvent system

The preparation and properties of bamboo lignocellulosic nanofibers based on deep eutectic solvent system

Utilization of benzoic acid–based green deep eutectic solvents for the fractionation of lignocellulosic biomass

The fractionation of lignocellulose utilizing green solvents is essential for the effective operation of biorefineries. In this study, a deep eutectic solvent (DES) system composed of benzoic acid (BA, hydrogen bond donor) and choline chloride (ChCl, hydrogen bond acceptor) was fabricated and successfully applied to the lignocellulose fractionation. The DES has low toxicity and little pollution. In this system, 67.8 % of lignin and 91.2 % of hemicellulose in poplar were removed, leaving 95.8 % of cellulose intact as solid residue. Due to the removal of the amorphous components, crystallinity of cellulose-rich water-insoluble solid (CIS) substantially increased from 55.6 % to 68.6 %, and CIS was used as feedstock for nanocrystalline cellulose preparation with excellent properties. The results showed that the obtained lignin had similar properties to CEL by GPC, FT-IR, 2D-NMR and TGA. A high-purity lignin rich in G units was recovered with a well-preserved structure, which has β–O–4 linkage content up to 53.01 %, low molecular weight, low polydispersity (1.99). Finally, the hydrolyzate can be used for fermentation. This study demonstrated that BA is suitable for DES design with excellent properties on lignin extraction, and this promising DES enable efficient pretreatment for economically feasible biomass conversion. This ChCl-BA DES facilitates environmentally friendly production of functional materials derived from cellulose and lignin under mild conditions.

Efficient leaching of valuable metals from spent lithium-ion batteries using green deep eutectic solvents: Process optimization, mechanistic analysis, and environmental impact assessment

The accumulation of over 11 million tons of spent lithium-ion batteries (LIBs) by 2030 highlights a critical environmental challenge posed by their large-scale retirement. The efficient recycling valuable metals from spent LIBs can both reduces environmental impact and mitigates the pressing issue of metal resource scarcity. In this context, deep eutectic solvents (DESs) have become a promising option as an eco-friendly solvent, exhibiting great potential for recycling spent LIBs. Therefore, this work proposed an innovative green DES system consisting of choline chloride (ChCl), DL-malic acid (MAL), and glycerol for the efficient leaching of valuable metals from spent LIBs. Comprehensive experiments were conducted to determine the optimum leaching conditions (130 °C, 60 g/L, MChCl:MAL:Glycerol of 1:1:3, 3 h), achieving high leaching efficiencies of 94.6% for Ni, 96.8% for Co, 93.8% for Mn, and 96.4% for Li. Through characterization techniques, kinetics studies, and density functional theory (DFT) calculations, the leaching process was predominantly governed by surface chemical reaction (1-(1-x)1/3 = kt) within the shrinking core model, exhibited activation energies of 49.89 kJ/mol, 47.66 kJ/mol, 50.51 kJ/mol, and 22.24 kJ/mol for Ni, Co, Mn, and Li, respectively. The propensity for DES to leach metal ions followed the order: Li > Co > Ni > Mn, determined by binding energy and energy gaps. Cl− and −COOH within the DES were capable of forming stable complexes with reduced transition metal ions, revealing an efficient coordination leaching mechanism. Additionally, a life cycle assessment (LCA) was conducted on the environmental impacts of the DES leaching process, confirming it as an effective and environmentally friendly method for recycling spent LIBs. This work avoided the employment of corrosive acids and alleviated the generally harsh conditions associated with DESs leaching, providing a viable solution for recovering spent LIBs.

Simultaneous extraction and deglycosylation for flavonoid analysis in Ginkgo biloba products using a two-phase deep eutectic solvent system

Total flavonoid content is one of the most important quality indicators of Ginkgo biloba leaves and its products, but the complex pretreatment procedures and the excessive use of organic solvents complicate the detection process. In response, an innovative and efficient two-phase deep eutectic solvent (DES) system—composed of an acidic hydrophilic DES and a hydrophobic DES—was developed to quantify flavonoids for quality control of G. biloba products. High-performance liquid chromatography (HPLC) detection conditions were optimized, followed by systematic screening and design of the two-phase DES system through adjustments to polarity, hydrophilicity, and acidity. Optimal pretreatment conditions were established through operating condition optimization. This approach enabled simultaneous extraction, deglycosylation, and enrichment of all flavonoids from G. biloba samples into the hydrophobic phase in a single step. Method validation showed strong linearity with a correlation coefficient (R2 > 0.9995). The detection (LOD) and quantification (LOQ) limits were between 0.35 and 0.37 mg/kg, and 0.92 and 0.96 mg/kg, respectively. The method also exhibited high sensitivity and accuracy, with a recovery rate of 96.91–100.39%. A greenness assessment with the ComplexGAPI tool confirmed this method’s eco-friendly advantages over conventional techniques, aligning well with green chemistry and economic principles. Ultimately, this technique effectively measured flavonoid levels in different G. biloba products. The method developed in this work not only enhances the efficiency of simultaneous extraction and deglycosylation by modifying the polarity, hydrophilicity, and acidity of the two-phase DES system, but also offers valuable insights for the advancement of environmentally friendly analysis technology for flavonoids.

A Low-cost and Green Zinc-Iron Battery Achieved by Ethaline Deep Eutectic Solvent.

Deep eutectic solvents (DESs) were considered as a potential electrolyte because of their low price, harmless to environment and wider electrochemical window potential compared to water. In this work, Fe(Ⅲ)/Fe(Ⅱ) and Zn(Ⅱ)/Zn redox couples were used as the positive and negative active materials, respectively, in a DES system using choline chloride and ethylene glycol in a molar ratio of 1:2 (ethaline). The possible working mechanism of the battery was studied by cyclic voltammetry, spectroscopic and simulation methods. The effects of different temperatures, concentrations of zinc ions in the anolyte and current densities on battery performance were evaluated. The results showed that the designed zinc-iron battery should preferably be operated at a current density of 0.5 mA cm-2 and the temperature of 313~323 K, which will improve the energy efficiency and maintain a high coulombic efficiency. The variation of cycle performance test presents a different pattern from the usual batteries, which is due to the effect of RO- group. At 313 K and 0.5 mA cm-2, the coulombic efficiency increases from 14.1% to 100.2% after 46 cycles, and then remains at about 100% during the rest 54 cycles, which demonstrates a good cycle stability of DES-based zinc-iron battery.

Multiphase Behavior of the Water + 1-Butanol + Deep Eutectic Solvent Systems at 101.3 kPa

The growing demand for more sustainable routes and processes in the mixture separation and purification industry has generated a need to search for innovations, with new solvent alternatives being a possible solution. In this context, a new class of green solvents, known as deep eutectic solvents (DESs), has been gaining prominence in recent years in both academic and industrial spheres. These solvents, when compared to ionic liquids (ILs), are more environmentally friendly, less toxic, low-cost, and easier to synthesize. In addition, they have significantly lower melting points than their precursors, offering a promising option for various applications in this industrial sector. Understanding and studying the thermodynamic behavior of systems composed of these substances in purification and separation processes, such as liquid–liquid extraction and azeotropic distillation, is extremely important. This work aimed to study the phase behavior of liquid–liquid equilibrium (LLE) and vapor–liquid equilibrium (VLE) of water + 1-butanol + DES (choline chloride + glycerol) systems with a molar ratio of 1:2. Experimental LLE data, obtained at 298.15 K and 101.3 kPa, and VLE data, obtained at 101.3 kPa and in the temperature range of 364.05 K–373.85 K, were submitted to the thermodynamic quality/consistency test, proposed by Marcilla et al. and Wisniak, and subsequently modeled using the gamma–gamma approach for the LLE and gamma–phi for the VLE. The non-random two-liquid (NRTL) model was used to calculate the activity coefficient. The results are presented for the VLE in a temperature–composition phase diagram (triangular prism) and triangular phase diagrams showing the binodal curve and tie lines (LLE). The separation and distribution coefficients of LLE were determined to evaluate the extractive potential of the DES. For the VLE, the values of the relative volatility of the system were calculated, considering the entrainer free-basis, to evaluate the presence or absence of azeotropes in the range of collected points. From these data, it was possible to compare DES with ILs as extracting agents, using data from previous studies carried out by the research group. Therefore, the results indicate that the NRTL model is efficient at correlating the fluid behavior of both equilibria. Thus, this study serves as a basis for future studies related to the understanding and design of separation processes.

Exploring Deep Eutectic Solvents as Pharmaceutical Excipients: Enhancing the Solubility of Ibuprofen and Mefenamic Acid.

Objectives: The study explores the potential of various deep eutectic solvents (DESs) to serve as drug delivery systems and pharmaceutical excipients. The research focuses on two primary objectives: evaluating the ability of the selected DES systems to enhance the solubility of two poorly water-soluble model drugs (IBU and MFA), and evaluating their physicochemical properties, including density, viscosity, flow behavior, surface tension, thermal stability, and water dilution effects, to determine their suitability for pharmaceutical applications. Methods: A range of DES systems containing pharmaceutically acceptable constituents was explored, encompassing organic acid-based, sugar- and sugar alcohol-based, and hydrophobic systems, as well as menthol (MNT)-based DES systems with common pharmaceutical excipients. MNT-based DESs exhibited the most significant solubility enhancements. Results: IBU solubility reached 379.69 mg/g in MNT: PEG 400 (1:1) and 356.3 mg/g in MNT:oleic acid (1:1), while MFA solubility peaked at 17.07 mg/g in MNT:Miglyol 812®N (1:1). In contrast, solubility in hydrophilic DES systems was significantly lower, with choline chloride: glycerol (1:2) and arginine: glycolic acid (1:8) showing the best results. While demonstrating lower solubility compared to the MNT-based systems, sugar-based DESs exhibited increased tunability via water and glycerol addition both in terms of solubility and physicochemical properties, such as viscosity and surface tension. Conclusions: Our study introduces novel DES systems, expanding the repertoire of pharmaceutically acceptable DES formulations and opening new avenues for the rational design of tailored solvent systems to overcome solubility challenges and enhance drug delivery.

Life cycle assessment and yield to optimize extraction time and solvent: Comparing deep eutectic solvents vs conventional ones

Deep eutectic solvents (DES) are gaining interest as eco-friendly alternatives for extracting bioactive compounds, but their environmental benefits remain unclear and need further evaluation. In this work, a case study of total polyphenols (TPC) extraction from spent coffee grounds (SCG) was environmentally evaluated using life cycle assessment (LCA). First, the most convenient extraction time (1, 10, 20, or 40 min) for water and acetone 20 % from an environmental perspective was identified. Second, a comparison of different solvents—DES (choline chloride-1,6-hexanediol), water, and ethanol 20 %—under their optimal extraction yield conditions was performed using literature data. Results from the first study revealed that the environmentally optimal extraction time (10 min) was not the one leading to the highest yield. The main contributors to the impacts were the use of acetone and electricity consumption.For the second study, DES performed worse in all studied environmental impact categories compared to both ethanol 20 % and water. Ethanol 20 % was the better option compared to water due to its higher extraction yield (9.2 mg vs. 6.5 mg TPC/g SCG, respectively). The environmental impacts associated with the DES system were primarily attributed to the DES preparation step, which requires virgin raw materials (e.g., dimethyl hexanediol), and the adsorption stage involving the use of resins. A sensitivity analysis was also conducted by optimizing the DES system to the best possible described conditions (90 % reuse of DES and maximum reduction of the macroporous resin used to adsorb the TPC after extraction). Nevertheless, the DES system still performed worse than water or ethanol 20 % systems, in 11 out of 16 impact categories.The study highlights the importance to consider environmental impacts and yield when optimizing extraction processes, especially at the laboratory scale, as the insights gained are valuable for improving eco-efficiency on an industrial scale.

Nitrogen‑sulfur doped graphene-loaded SiO2/Co9S8 composites as anode materials for improved lithium storage

Heteroatom-doped graphene lamellae can effectively modulate the physical and chemical surface activities of Co9S8 materials. The addition of a second dopant atom, such as nitrogen (N) can further improve the composite properties. Herein, novel nitrogen‑sulfur double-doped graphene-loaded SiO2/Co9S8 composites (SiO2/Co9S8@NSG) were prepared by a one-step solvothermal method using polyethylene glycol as the carbon source and cobalt chloride hexahydrate as the cobalt source to yield a Deep Eutectic Solvents (DESs) system. The precursor was then obtained by adding tetraethyl silicate as the silicon source, thiourea as the sulfur source, and urea as the nitrogen source. The uniform distribution of Co9S8 in the N/S-doped graphene matrix formed graphene-coated SiO2 particles SiO2/Co9S8@NSG with high specific surface area, superior ionic conductivity, and elevated theoretical specific capacity. The N/S co-doped graphene matrix not only improved the electrical conductivity and hindered the adhesion of the particles, but also buffered the volume of the Co9S8 change and enhanced the electrochemical performance. The testing of SiO2/Co9S8@NSG composite as an anode for lithium-ion batteries (LIBs) revealed an impressive specific capacity with reversible capacity of 850 mA h/g after 900 cycles at a current density of 0.5 A/g and multiplicative capacity of 730 mA h/g at a current density of 0.1 A/g, confirming excellent cycling stability and a Coulombic efficiency close to 100 %. Overall, the proposed doping strategy looks promising for the development of high-performance LIBs.

Probing the role of hydrogen bond donors on the speciation and electrochemical behavior of Eu(III) in choline chloride-based DESs

This study explores the electrochemical properties and speciation of Eu(III) ions in choline chloride (ChCl)-based deep eutectic solvents (DESs), focusing on how different hydrogen bond donors—urea (U), ethylene glycol (EG), and malonic acid (MA)—influence the stability of europium complexes. Employing electrochemical methods, spectroscopic analysis, and theoretical approaches, the research examines how changes in hydrogen bonding during complexation affect Eu(III) coordination. Cyclic voltammetry highlights the role of complex formation and DES viscosity in controlling mass transport and electron transfer rates. Theoretical and experimental data show that the ChCl:1MA DES forms the most stable europium complex, driven by strong hydrogen bonding and robust Eu-DES interactions, as supported by optimized geometries and favorable electrochemical stability. This stability is further confirmed by the high negative binding and formation free energies of Eu(NO3)3·5H2O in all three DES systems. Photoluminescence spectroscopy reveals fluorophore formation due to interactions between hydrogen bonds and functional groups such as –NH2, –COOH, and –OH, enhancing the understanding of Eu3+-DES complexes for potential applications in materials science. By clarifying how hydrogen bond donors affect Eu(III) speciation and reactivity, this research advances lanthanide chemistry in DESs and opens avenues for designing Eu(III)-based materials with specialized properties for various technological uses.

Efficient ultrasonic extraction of alkaloids and glycosides from Camptotheca acuminata Decne via deep eutectic solvents: Kinetics and mechanisms

The study investigated the extraction of alkaloids and glycosides from the Camptotheca acuminata Decne using deep eutectic solvent (DES). 18 types of deep eutectic solvents (DESs) were prepared, and it was found that the extraction performance of choline chloride (ChCl)-formic acid (FA) was optimal, surpassing traditional solvents such as methanol/70 % methanol. In comparison to methanol, the extracted amount of compounds by DES was 2–3 times higher. The extraction processes involving the molar ratio of ChCl-FA, pH, DES/H2O mass ratio, solid/liquid ratio, as well as ultrasonic power were optimized. A mathematical model for solid/liquid extraction kinetics from Camptotheca acuminata Decne was developed. The extraction mechanism was investigated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and 1H nuclear magnetic resonance(1H NMR). The results revealed that the DES caused dissociation in Camptotheca acuminata Decne and formed hydrogen bonds with Camptothecin (CPT). Meanwhile, density functional theory (DFT) calculations verified that FA-based exhibited the highest extracted amount for CPT. In addition, this study investigated the recovery rate of DES, and the results showed that after 10 cycles, the DES system remained effective for the extraction of alkaloids and glycosides.

Molecular-Scale Interactions in the Choline Chloride-Ethylene Glycol Deep Eutectic Solvent System: The Importance of Chromophore Charge in Mediating Rotational Dynamics.

We report on the rotational diffusion dynamics of three chromophores (disodium fluorescein, oxazine 725, and perylene) in a series of choline chloride-ethylene glycol (ChCl:EG) deep eutectic solvent (DES) systems. We observe behavior independent of DES bulk viscosity for the cationic and neutral probes and behavior that is consistent with stick-limit interactions for the modified Debye-Stokes-Einstein model for the anionic probe. This finding indicates that the anionic species is integral to the interactions between DES constituent species that are responsible for local organization, consistent with previous MD simulations that showed higher interaction energies associated with both the hydrogen bond donor (EG) and hydrogen bond acceptor (Ch+) interactions with Cl- in ChCl:EG mixtures. The reorientation data reported here also indicate a region around 15 mol % ChCl where the stoichiometric relationship between the species gives rise to changes in the details of intermolecular interactions.

Tailoring novel glycerol-potassium iodide deep eutectic solvents: A comprehensive investigation of physical, structural, and electrochemical properties

A novel Deep Eutectic Solvent (DES) can be formed between glycerol (Gly) and potassium iodide (KI). This study presents a comprehensive physicochemical characterization of these designed DES. The DES compositions, DES-Gly-KI and DES-Gly-KI-EtOH, consist of a hydrogen bond donor (Gly), a hydrogen bond acceptor (KI), and a viscosity-reducing solvent (ethanol (EtOH)). Experimental methodologies, including UV–VIS spectroscopy, mass spectrometry, Fourier transform infrared spectroscopy, and rheological studies such as density and viscosity, are employed to elucidate molecular interactions and structural characteristics. Karl Fischer titration is also conducted to analyze the moisture content in this prepared DES systems. The electrochemical performance of supercapacitors is also analyzed using cyclic voltammetry and electrochemical impedance spectroscopy. The specific capacitance values are found to be 10.32 F/g and 19.18 F/g for DES-Gly-KI and DES-Gly-KI-EtOH-5, respectively. The findings contribute in understanding DES behaviour, reveal distinctive physicochemical attributes, offering valuable insights into crafting and optimizing novel DESs, which is customized to meet distinct industrial requirements.

Deep eutectic solvent strategy for green extraction of chlorogenic acid from sea buckthorn: optimization and sustainability

BackgroundSea buckthorn (Hippophae rhamnoides), a deciduous species plant, is widely distributed around the globe, and native to the cold-temperate regions of Europe and Asia. This medicinal herb contains several bioactive constituents including chlorogenic acid. The conventional methods used for the extraction of phenolic antioxidants from natural herbs often result in low yields, high toxicity, and pose environmental hazards limiting their effectiveness and scalability. Therefore, green extraction techniques using deep eutectic solvents, composed of natural, non-toxic, and biodegradable components were applied for extraction of chlorogenic acid from sea buckthorn weed. Fourteen deep eutectic solvent mixtures were prepared and evaluated for extraction yield of chlorogenic acid. Parameters such as hydrogen bond donor-to-hydrogen bond acceptor ratio, liquid-to-solid ratio, shaking speed, and shaking time were optimized for the best mixture.ResultsThe combination of lactic acid and maltose (1:1) was found to give best extraction yield using response surface methodology. The deep eutectic solvent system under optimum conditions produced 12.2 g/100 g of crude extract sea buckthorn containing 174.7 mg gallic acid equivalents (mg GA)/g) of extract. Moreover, the optimized extract exhibited appreciable radical scavenging capacity (91%), trolox equivalent antioxidant capacity (11.2% of extract), and inhibition of peroxide in linoleic acid (80.6%). High-performance liquid chromatography-based characterization revealed the extracts contained chlorogenic acid (20.1 mg/g of extract) as the major constituent.ConclusionsIn summary, the adoption of DES for the extraction of bioactive phenolic constituents from sea buckthorn offers multiple benefits, including economic efficiency, enhanced extraction performance, and environmental sustainability. The findings of this study not only advance the understanding of DES in phytochemical extraction but also pave the way for broader application of green solvents in the natural products industry. Future research should focus on further optimizing DES formulations and scaling up the extraction process to fully realize the potential of this innovative extraction method in commercial applications.

A novel temperature-responsive biphasic deep eutectic solvent-based solvent system: Integrated efficient extraction, enrichment and recovery of phytochemicals

The current large-scale use of organic and some toxic reagents hinders the development of plant secondary metabolite extraction and processing industry. Here, a biphasic temperature-responsive solvent system consisting of hydrophilic deep eutectic solvent (choline chloride: levulinic acid) and fatty acid-based hydrophobic deep eutectic solvent is developed. Some characteristics of this intelligent solvent system, including hundreds of synthesis ratios and corresponding switching temperatures, phase ratios, etc., have been comprehensively determined. Subsequently, it is applied to different plant matrices. The extraction efficiencies ranged from 1.006 to 6.807 times higher than those of conventional organic reagents, with separation efficiencies ranging from 60.7 % to 100 %, besides the fact that the hydrophilic components are almost entirely distributed in the lower phase. The recovery of targeted phytochemicals achieves satisfactory results during the simultaneous extraction and enrichment process. Mechanisms of switching, extraction, and enrichment have been elucidated to a certain extent from the point of view of chemical computational simulations. Overall, this new green solvent system is universal and can be applied to a wide range of phytochemicals extraction and separation from plants in a one-pot operating unit. Also, it is almost the greenest of the temperature-responsive solvents studied so far and has superior application prospects.

Absorption-Desorption Characteristics of the Synthesized Deep Eutectic Solvents for Carbon Dioxide Capture

The development of an environmentally friendly CO2 absorbent with significant energy utilization which can be an alternative to CO2 capture by an ethanolamine solution is presently an obligatory issue. In this work, binary and ternary deep eutectic solvents (DESs) were prepared according to their CO2 absorption/desorption performances. A series of DESs comprise different hydrogen bonding donor (HBD)- acceptor (HBA) pairs as CO2 capturing solvents; HBAs include choline chloride (ChCl) and tetrabutylammonium bromide (TBAB), and selected amines are represented as HBDs and include monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA). Binary DESs synthesized of ChCl/MEA, ChCl/DEA, ChCl/TEA, TBAB/MEA, TBAB/DEA, and TBAB/TEA in a CO2 absorption cell at a mole ratio of 1:4. While selected amidines were represented as super-based (SB) and included 1,5-Diazabicyclo [4.3.0] non-5-ene (DBN) and 1,8-Diazabicyclo [5.4.0] undec-7-ene (DBU). The ternary DESs were prepared by adding DBN or DBU to the binary DESs system in a (1:4:3) molar ratio. CO2 absorption experiments were attained at atmospheric pressure and a temperature of 30 °C using 15 vol.% CO2 with 85 vol.% N2. On the other hand, the regeneration process for DESs was conducted at 90 oC. Binary DES synthesized from ChCl/MEA gives a higher absorption rate of CO2 of 0.0177 mole/kg. min, CO2 absorption loading of 2.9092 mole CO2/kg solvent, cyclic loading of 2.0001 mole CO2/kg solvent, and a regeneration efficiency of 68.75%. The synthesis DESs showed a better performance compare with a common Ionic liquids.

Biphasic Production of 5-hydroxymethylfurfural (HMF) in a Recyclable Deep Eutectic Solvent-based System Catalyzed by H4SiW12O40.

The reaction with in situ extraction to yield 5-hydroxymethylfurfural (HMF) from Fru was investigated using a biphasic system based on a self-consuming deep eutectic solvent (DES) as reaction phase. The significance of choline chloride (ChCl), a cost-effective and safe quaternary ammonium salt, was evident in enhancing 5-HMF yield through fructose dehydration and concurrently suppressing side reactions. The DES system demonstrated fast reactions with high selecivities and recyclability across five cycles. The observed decline in H4SiW12O40 activity, primarily due to proton leaching, was successfully restored with the addition of HCl. Furthermore, ChCl exhibited ease of recrystallization in the presence of acetonitrile. This research proposes an environmentally friendly approach for 5-HMF production through a reusable-biphasic process. The presented reaction system suppresses completely the formation of levulinic and formic acid leading to HMF yields of up to 84% of selectivities of up to 88% after 30 minutes at 80 °C. The system was recycled over 16 runs and after an initial slight loss of activity the system in the run 0-5, run 6-15 has shown a constant HMF output as in the first recycling run.

An experimental-computational study on thermodynamic properties and intermolecular interactions of binary mixtures composed of quaternary ammonium salts-based deep eutectic solvents and [ETN] or [ACN]

To deep understand the thermodynamic properties and intermolecular interactions of quaternary ammonium salts-based deep eutectic solvents (DESs), two novel DESs systems ([TPAB]:[MA] and [TBAB]:[MA]) were synthesized using tetrapropylammonium bromide ([TPAB]) or tetrabutylammonium bromide ([TBAB]) as hydrogen bond acceptor (HBA) and malonic acid ([MA]) as hydrogen bond donor (HBD). Then, the ethanol (ETN) and acetonitrile (ACN) were used to prepare four DESs + solvent mixtures. Based on experimental data of density and surface tension of these four binary mixtures, the thermodynamic parameters such as apparent molar volume (Vϕ), excess molar volume (VE), limiting apparent molar expansibility (E0ϕ), molar surface entropy (s), molar surface Gibbs energy (gs), and molar surface enthalpy (h) were calculated. At the same temperature, the calculated VE values of binary mixtures were arranged in the following sequence: [TBAB]:[MA] + [ETN] > [TPAB]:[MA] + [ETN] > [TPAB]:[MA] + [ACN] > [TBAB]:[MA] + [ACN]. Based on the radial distribution functions (RDFs) theory, this observed phenomenon was attributed to the enhanced interaction between HBA and [ETN] in the DESs + [ETN] as compared to the interaction between HBA and [ACN] in the DESs + [ACN]. The predicted surface tension values (γ(pre)) of the four binary mixtures were calculated and highly correlated with the experimental surface tension values (γ(exp)). Moreover, the Br1 atom in [TPAB], the Br2 atom in [TBAB], and the H9 atom in [MA] were selected as reference sites. The interaction strength sequence between HBD and HBA was investigated using RDFs as follows: [TBAB]:[MA] + [ACN] > [TPAB]:[MA] + [ACN] > [TBAB]:[MA] + [ETN] > [TPAB]:[MA] + [ETN]. This study can provide an important theoretical support for further utilization of quaternary ammonium salts-based DESs.