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of molecular formula and molecular weight of choline chloride (ChCl), lactic acid, oxalic acid and tartaric acid used in the present work.
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In this study, a new type of " green solvents " named deep eutectic solvents (DESs) has been synthesized combining hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs). Choline chloride (ChCl) was chosen as typical HBA, and lactic acid, tartaric acid, citric acid and oxalic acidwere chosen as HBDs. The thermal stability of deep eutectic s...
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... chloride (≥98%, Sigma Aldrich), tartaric acid (99.5 %), citric acid× H 2 O(p.a.), lactic acid (90 %, VWR ® )and oxalic acid × 2H 2 O (p.a.)were used as received without further purification except drying for 24 h at 50°C under vacuum to reduce the moisture content to minimum. The details of molecular formula and molecular weight of all components are shown in Table 1. ...Citations
... A major weight loss occurred at this peak, with 74.69% of the sample decomposed. The majority of DES degradation occurs in the region of 190-280 °C [23]. The presence of a broader peak may suggest a multi-step degradation process, followed by a secondary reaction or a phase transition. ...
Deep eutectic solvents (DESs) are environmentally friendly compounds that can be synthesized through the combination of hydrogen-bond donors and acceptors. The diverse applications of DESs underscore their potential as catalysts in various chemical reactions. In this study, an acidic DES was prepared as a catalyst for levulinic acid (LA) esterification with ethanol to produce ethyl levulinate (EL). The acidic DES was prepared from choline chloride and sulfanilic acid through thermal mixing. Characterization of the DES was conducted using Fourier transform infrared-attenuated total reflectance and nuclear magnetic resonance spectroscopy analysis to identify its functional groups and confirm the structure. Additionally, the thermal stability of the DES was analyzed using thermogravimetric analysis, while its acidity was determined using acid-base titration. The esterification of LA with ethanol was assessed under reflux conditions at 80 °C, with specific parameters examined: the molar ratio of LA to ethanol (ranging from 1:5 to 1:13), the ratio of LA to DES (ranging from 1:0.4 to 1:1.4), and the reaction duration (0.5–5 h). The DES used in this work showed an acidity of 2.89 mmol/g. The optimum conditions were obtained at a 1:7 molar ratio of LA to ethanol, a 1:1.2 ratio of LA to DES, and 3 h of reaction time at 80 °C, resulting in 99% conversion of LA to EL. This finding highlights the remarkable catalytic performance of the choline chloride/sulfanilic acid DES in facilitating a highly efficient conversion of LA to EL. Copyright © 2025 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).
... Since these solvents are held together by ionic bonds or hydrogen bonds, certain high reservoir temperatures will cause the bonds between particles to break down and lose its effects. 13,14 The temperature effect on solvents can be assessed by running through thermogravimetric analysis (TGA). TGA will show that with an increase in temperature, the stability of the solvents begins to decline and the temperature limit where the bonds of the solvent particles begin to disintegrate will be determined. ...
Fines migration can cause various issues, such as plugging of the sand screen and damage to tubings. There are two chemical sand control methods: consolidation and agglomeration. Consolidation works by injection of a solvent into the formation to harden over time and hold the sand in place, while agglomeration works by altering chemical properties of the sand surface to attract and clump up sand. Various chemicals have been used for research in sand control. Some chemicals for consolidation, mostly resins, have been effective in consolidating sand but may cause permeability impairment, which will reduce production. Some chemicals for agglomeration such as a polymer with amines have been less effective or are nonbiodegradable. In this work, a novel deep eutectic solvent (DES) and ionic polymer combination as a fines stabilizer is formulated in-house and tested through extensive experimental study. The development of chemicals is based on agglomeration principles which determine the range of zeta potential reduction that can be achieved to destabilize, coagulate, and flocculate the fine particles together with different combinations of DESs and ionic polymers tested systematically using the design of experiment (DoE) method. The chemicals are then tested for compatibility with reservoir fluids in the jar test. The optimized formulation is characterized by thermogravimetric analysis (TGA) for limit of temperature degradation and laser particle size analysis (LPSA) for the extent of particle size. The novelty of this work is the development of a greener and more cost-saving in-house DES and ionic polymer combination as a fines stabilizer chemical, which is effective for both injection or production wells after stimulation or enhanced oil recovery (EOR) treatments. Due to the tunable nature of the DES, the formulated chemical can be tailored for various reservoir conditions to cater to specific requirements.
... DESs, which are eutectic salt mixtures with a lower melting point compared to their discrete components (Abbott et al., 2018), show the advantage of minimizing the use of water in metal processes (Peeters et al., 2020), reducing hydrogen embrittlement phenomena (Simka et al., 2009;Ismail, 2020), and avoiding hydroxide and oxide incorporations, which may negatively impact the quality in metal production (Yuliy and Gamburg, 2011). In recent times, there has been a significant interest in the study of DES properties, including their thermal stability (Delgado-Mellado et al., 2018), (Jablonsky, 2016), cytotoxicity (Hayyan et al., 2013), and conductivity , (Wang et al., 2014). DESs have been proven to be chemically stable, relatively nontoxic, and able to dissolve metal salts (Rodriguez Rodriguez et al., 2020), while presenting high conductivity (Zhang et al., 2012). ...
... Studies of DES thermal stability remain scarce, probably due to the generally accepted idea that they are highly thermally stable and nonvolatile. Haz et al. (92) reported the first work with dynamic thermogravimetric analysis of DESs. The authors showed that choline:organic acids had an onset decomposition temperature between 135°C and 200°C. ...
Are deep eutectic solvents (DESs) a promising alternative to conventional solvents? Perhaps, but their development is hindered by a plethora of misconceptions. These are carefully analyzed here, beginning with the very meaning of DESs, which has strayed far beyond its original scope of eutectic mixtures of Lewis or Brønsted acids and bases. Instead, a definition that is grounded on thermodynamic principles and distinguishes between eutectic and deep eutectic is encouraged, and the types of precursors that can be used to prepare DESs are reviewed. Landmark works surrounding the sustainability, stability, toxicity, and biodegradability of these solvents are also discussed, revealing piling evidence that numerous DESs reported thus far, particularly those that are choline based, lack sufficient sustainability-related traits to be considered green solvents. Finally, emerging DES applications are reviewed, emphasizing their most remarkable feature: the ability to liquefy a solid compound with a target property, allowing its use as a liquid solvent.
Expected final online publication date for the Annual Review of Chemical and Biomolecular Engineering, Volume 14 is June 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
... Representative thermal profiles obtained for a DES and its precursors (HBD and ChCl) are reported in Fig. 2a. [5]; c: [6]; d: [7]; e: [8]; f: [9]; g: [10]; h: [11]; i: [12]; m: [13] n: [14]. [8] with the first one preferred; c) practical guide for a correct evaluation of DES thermal stability; d) graphical determination of T onset and T peak on a dynamical TGA performed on DES 3 (DES number ID reported in Fig. 1) at 20 C/min. ...
Deep eutectic solvents (DESs) are a class of versatile and green emerging materials. Despite the huge amounts of applications proposed in the last years, studies on their thermal stability are often missing. In this short review, we propose a guide for a correct evaluation of DES thermal stability, conducted mainly by dynamical thermogravimetry (TGA). We collected all the data reported in the literature on choline chloride (ChCl)-based DESs, as proof of concept to show the potentialities of the technique, highlighting all the parameters that need to be considered for a correct analysis, with particular attention to the possible sources of misleading interpretations (e.g. the adsorbed water, or the formation of undesired products during DES preparation). In many cases, the additional use of isothermal TGA, or TGA coupled with online techniques such as Fourier Infra-Red Spectroscopy or Mass Spectrometry, may help for the data interpretation. Besides, we summarize in a graph the degradation temperatures of many DESs and their precursors, intended as an operative guide to choosing the correct DES for different applications. The findings reported to date, highlight the potentialities of thermal analysis on DESs, as a powerful tool to obtain essential information on their applicability, and to implement the knowledge of their nanostructure from a molecular point of view.
... Major thermal degradation of the Glu:Gly occurred at a higher temperature in two steps [42]. Glu-Gly is more stable at higher temperatures. ...
Amino acid-based deep eutectic solvents (AADESs) are emerging type of DESs with a wide range of applications. In this study, two novel AADESs were formulated using basic, L-(+) arginine (Arg), and acidic, L-glutamic acid (Glu), amino acids as hydrogen bond acceptors (HBA) and glycerol (Gly) as the hydrogen bond donor (HBD) at a 1:3 molar ratio. The eutectic points of the formulated AADESs were found to be -0.14°C for Glu-Gly and -1.36°C for Arg-Gly. The successful interactions among the constituents were investigated using FT-IR, ¹H-NMR spectroscopy, and mass spectrometry. These studies found that Glu-Gly could form ester impurities. However, the mass spectrometry showed that the impurities are negligible. The TGA revealed that both DESs could be applied up to 150-160°C without losing weight, while Glu-Gly could be used up to 200°C. Formation of Arg-Gly was strongly dominated by glycerol, while Glu-Gly DES was formed by an equal contribution of both components. Principal component analysis (PCA) helped to visualize the spectroscopic outcomes. Since AADESs are excellent pretreatment media for biomass, lignin was treated as a model biomass in this study with the formulated AADESs to determine their reaction products. It was found that Arg-Gly can isolate only one monomeric compound (4-methyl benzaldehyde), while Glu-Gly can isolate three monomeric compounds. Oxidative depolymerization of the lignin residues validated the outcomes obtained from the AADES-lignin reactions. Glu-Gly was more efficient for lignin depolymerization because of its smaller viscosity, higher stability, acidic environment, and stronger hydrogen bond formation between lignin and glycerol.
... However, when water is present DES systems, degradation by esterification is minimized due to the hydrolysis of the ester being favored by the presence of water (Smink et al., 2020). Indeed, Haz et al. showed that the lactic acid -ChCl DES is stable under pulping conditions up to 190°C (Haz et al., 2016). ...
Deep eutectic solvents (DESs) are considered as a green and environmentally benign solvent class for various applications, including delignification of biomass. One of the major challenges in the delignification of biomass by DES is attributed to the limitations in mass transfer. By subjecting wood chips to a low-energy mechanical refining, i.e., the Asplund process, the accessible surface area increases greatly, which in turn improves the mass transfer and increases the reaction rate. In this research, the DES delignification of Asplund fibers made of Norway spruce was studied as a strategy to produce papermaking fibers under mild conditions. A DES consisting of lactic acid and choline chloride was used due to its proven performance in delignification. Various operational conditions, such as temperature, time, DES-to-wood ratio, and the type of stirring were studied. A novel parameter, Q, allowed to evaluate the impact of the operational conditions on the quality of the pulp in terms of delignification degree and fiber length. The results showed that cooking temperature had the most significant effect on the pulp quality. Additionally, it was observed that cooking times between 30 and 45 min result in a pulp yield of about 50%, while fibers have a lignin content of about 14% and a fiber length of 0.6 mm. These results demonstrate that it is possible to obtain fibers of relatively good quality from DES delignification using Asplund fibers as the starting material.
... The decomposition temperature (T dec ) is one of the striking thermophysical properties as it decides the most extreme temperature at which a DES can exist as a fluid without any deterioration of its physical/chemical properties as a solvent. From the literature survey it was accounted that the presence of additional HBDs may significantly influence the thermal stability of pure DES [30,45,46]. ...
Eutectic mixtures, in particular, the deep eutectic solvents (DESs) are gaining an overwhelmingly research interest as green solvents and is emerging as an attractive replacement to ionic liquids (ILs) for a variety of industrial applications. In this milieu, we have prepared green DESs by combining choline chloride (ChCl) as hydrogen bond acceptor (HBA) with malonic acid (MA) and ethylene glycol (EG) as hydrogen bond donors (HBDs) at capricious molar ratios. The influence of HBD (their nature and molar ratio) on the prepared DES structure along with the thermophysical properties viz., decomposition temperature, density, speed of sound, electrical conductivity, viscosity, rheology, refractive index, and electrochemical potential window (EPWs) have been experimentally witnessed as a function of temperature. The amendment in the hydrogen bonding networks with the successive addition of HBDs in different molar ratios was evidently inferred using Fourier transform-infrared (FT-IR) spectroscopy. Different thermodynamic models were employed to describe and correlate the obtained results from the measured thermophysical properties. Additionally, the thermal expansion coefficient (αP), free length (Lf), molar entropy (So), isentropic compressibility (κs), molar polarizability (Rm), and free volume (fm) have been calculated based on the experimentally determinedρ, u, and nDrespectively. The cyclic voltammetry (CV) outcomes were rationalized which provided a broad range of Electrochemical potential windows (EPWs) due to the delocalization of charged moieties. In addition, the viscoelastic and rheological measurements exhibited a Newtonian-like behavior. The impact of the varying molar ratio of HBD in the prepared DESs were also perceived for the enhancement of the selected poorly-water soluble metal oxides dissolution with a purpose of making these prepared DESs more promising green solvent for various electro-deposition possesses.
... The thermograms and derivative thermogravimetry (DTG) curves of Lact:Tart: ChCl (4:1:1) are shown in Fig. 9. DES degradation occurs at a wide temperature range, between 150 and 300°C, with the highest degradation stage at 192°C. The decomposition profile of this DES is similar to those observed by Haz et al. for binary Lact:ChCl and Tart:ChCl DES [61]. Lactic acid is reported to show the maximum weight loss rate at approximately 190°C [61,62]. ...
... The decomposition profile of this DES is similar to those observed by Haz et al. for binary Lact:ChCl and Tart:ChCl DES [61]. Lactic acid is reported to show the maximum weight loss rate at approximately 190°C [61,62]. As the major component of DES, it was expected that lactic acid degradation would correspond to the highest weight loss observed during DES heating. ...
Lignocellulosic biomass is a renewable and sustainable feedstock, mainly composed of cellulose, hemicellulose, and lignin. Lignin, as the most abundant natural aromatic polymer occurring on Earth, has great potential to produce value-added products. However, the isolation of highly pure lignin from biomass requires the use of efficient methods during lignocellulose fractionation. Therefore, in this work, novel acidic deep eutectic solvents (DES) were prepared, characterized and screened for lignin extraction from maritime pine wood (Pinus pinaster) sawdust. The use of cosolvents and the development of new DES were also evaluated regarding their extraction and selectivity performance. The results show that an 1 h extraction process at 175 °C, using a novel DES composed of lactic acid, tartaric acid and choline chloride, named Lact:Tart:ChCl, in a molar ratio of 4:1:1, allows the recovery of 95 wt% of the total lignin present in pine biomass with a purity of 89 wt%. Such superior extraction of lignin with remarkable purity using a “green” solvent system makes this process highly appealing for future large-scale applications.
... This means that the formed degradation product (the ester between lactic acid and choline chloride) reacts back to the initial DES, and especially by operating the pulping stage wet, the presence of water dramatically reduces the esterification of lactic acid. Haz et al. (2016) determined that a DES comprised of lactic acid and choline chloride was stable up to 197 • C, meaning the used DES is thermally stable at the operating conditions used in this work. ...
Deep eutectic solvents (DES) have been proposed as solvents for biomass delignification. This paper describes a conceptual process design for the delignification of Eucalyptus globulus using a DES comprised of 30 wt % choline chloride and 70 wt% lactic acid. In this design, the lignin and hemicellulose by-products are recovered by liquid–liquid extraction using 2-MTHF as solvent. Material and energy balances were made and the energy usage of the process was optimized with additional experiments. The amount of DES was reduced to the minimal amount required to fill the porous biomass (5 kg per kg wood), which only reduced the delignification from 94% to 87% and increased the yield from 57 to 59%. Direct recycling of lignin-in-DES mixtures without lignin removal by liquid–liquid extraction to the delignification stage may save energy, but increased repolymerization increases the lignin’s molar weight, which decreases its value and makes recovery by liquid–liquid extraction more difficult. After optimization, the total heat duty ofthe proposed process is 7.9 GJ/t pulp, which is 28% lower than the kraft process. The main benefit of DES based delignification processes is the possible valorization of byproducts, such as lignin and furans from hemicellulose.
