THERMAL STABILITY OF SELECTEDDEEP EUTECTIC SOLVENTS (original) (raw)
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Properties and thermal behavior of natural deep eutectic solvents
Journal of Molecular Liquids, 2016
Natural deep eutectic solvents (NADES) have shown to be promising sustainable media for a wide range of applications. Nonetheless, very limited data is available on the properties of these solvents. A more comprehensive body of data on NADES is required for a deeper understanding of these solvents at molecular level, which will undoubtedly foster the development of new applications. NADES based on choline chloride, organic acids, amino acids and sugars were prepared, and their density, thermal behavior, conductivity and polarity were assessed, for different NADES compositions. The NADES studied can be stable up to 170°C, depending on their composition. The thermal characterization revealed that all the NADES are glass formers and some, after water removal, exhibit crystallinity. The morphological characterization of the crystallizable materials was performed using polarized optical microscopy which also provided evidence of homogeneity/phase separation. The conductivity of the NADES was also assessed from 0 to 40°C. The more polar, organic acidbased NADES presented the highest conductivities. The conductivity dependence on temperature was well described by the Vogel-Fulcher-Tammann equation for some of the NADES studied.
Thermal stability of choline chloride deep eutectic solvents by TGA/FTIR-ATR analysis
Journal of Molecular Liquids, 2018
Deep eutectic solvents (DESs) based on the cation choline have been proposed to date for a variety of applications due to their remarkable physicochemical properties. The thermal stability is one of the first properties of DESs that needs to be known since it limits the maximum operating temperature for which these solvents are useful in many applications. In this work, the thermal stability of eight different choline chloride-based DESs formed using levulinic acid, malonic acid, glycerol, ethylene glycol, phenylacetic acid, phenylpropionic acid, urea, and glucose as hydrogen bond donors (HBDs) has been studied using isothermal and dynamic thermogravimetric analysis/Fourier transform infrared-attenuated total reflectance spectroscopy (TGA/FTIR-ATR) techniques. Isothermal and dynamic FTIR-ATR were carried out to confirm the formation and to show the structural changes with temperature of the DESs, respectively. The onset decomposition temperatures of the DESs were obtained from dynamic TGA. However, the maximum operating temperatures determined by isothermal TGA in long-term scenarios have demonstrated to be significantly lower than the onset decomposition temperatures for every DES studied. The thermal stability and the boiling point of HBDs have a crucial impact on the maximum operating temperature of DESs.
Diethylene glycol based deep eutectic solvents and their physical properties
Studia Universitatis Babeș-Bolyai Chemia, 2017
In this study, diethylene glycol (DEG), as a hydrogen bond donor (HBD), was mixed with three ammonium based salts, namely N,Ndiethylethanolammnium chloride, tetra-n-butylammonium bromide and choline chloride, as well as two phosphonium based salts, namely benzyltriphenylphosphonium chloride and methyltriphenylphosphonium bromide, to prepare five different deep eutectic solvents (DESs) series. The DESs freezing points and functional groups were investigated. In addition, the physical properties viscosity, density, conductivity and surface tension were determined as function of temperature in the particular temperature range of 293.15-353.15 K. It is worth mentioning that all examined DESs were stable and in liquid phase at room temperature which emphasize their promising potential to be utilized as inexpensive environment-friendlier solvents. Owing to their low recorded freezing points and viscosities, DEG based DESs can be effortlessly processed without any further heating required in diverse industrial applications.
Investigation of improved applications of deep eutectic solvents in various fields
2021
In the pharmaceutical arena, the most significant issue is green technology. This is due to the fact that, it decreases the cost of drugs, reducing the environmental influence of the arena and improving the human health and safety. Deep eutectic solvents (DES), a novel kind of green solvent, have some focused attributes such as, low vapor pressure, high thermal stability, low cost, biodegradability, and high viscosity. Green solvent metrics with attention to functionality and environmental, safety, and health influences from a progression and life cycle view are likewise addressed and practical to common and unique solvents.As a developing research field, DESs have previously received important research consideration from chemistry scientists.
Triethylene glycol based deep eutectic solvents and their physical properties
Deep eutectic solvents (DESs) have been recently emerged as new ionic liquids (ILs) analogues. The low vapor pressure, inflammability, biodegradability and positive effect on the environment make DESs more favorable as neoteric solvents. In this study, triethylene glycol (TEG) was selected as a hydrogen bond donor (HBD) to form DESs with five types of phosphonium and ammonium salts, namely methyltriphenylphosphonium bromide (MTPB), benzyltriphenylphosphonium chloride (BTPC), allyltriphenylphosphonium bromide (ATPB), choline chloride (2-hydroxyethyl-trimethylammonium) (ChCl) and N,N-diethylenethanolammonium chloride (DAC). The physical properties of the synthesized DESs were measured such as freezing point, viscosity, electrical conductivity, Walden rule, density, pH and water content. In addition, the Fourier transform infrared spectroscopy (FTIR) was employed to study the functional groups. The experiments were conducted at different temperatures, i.e. 25–80 °C. It was found that DESs have suitable properties to be used in industrial processes such as separation, extraction, biochemical, petroleum and gas technology.
Properties and green applications based review on highly efficient deep eutectic solvents
Egyptian Journal of Chemistry
D EEP eutectic solvents (Ionic liquids)(DESs), a new type of low cost and eco-friendly solvent, have fascinating rising interest in chemistry. To recapitulate the properties and significance of deep eutectic solvents (DESs), this review focus on characteristics of deep eutectic solvents, as well as their applications in electrochemistry, catalytic activity, biodegradability, bio-catalysis, as aromatic hydrocarbons, extraction and separation. The existing data and references are appraisal to go over the developments of DESs.
Arabian Journal for Science and Engineering, 2017
Deep eutectic solvents are a recent class of solvents that started to get attention to replace the ionic liquids and, of course, the traditional organic solvents. In this work, two series mixtures of choline chloride-urea-glycerol and choline chloride-malic acid-glycerol, liquids at room temperature, were synthesized in different molar ratios and their properties were studied. Electrochemical characterization test was performed using Pt/C catalyst and the results showed an interesting electrochemical stability for choline chlorideurea-glycerol mixture within the potential range of −1 to 1 V. The viscosity was reported as a function of temperature for mixtures which behaved as Newtonian fluids and as a function of shear rate for those which behaved as non-Newtonian fluids. For instance, 1-1-1 choline chloride-urea-glycerol viscosity was decreased from 706.8 to 26.9 cP when the temperature was increased from 20 to 80 • C, respectively. While for the same mixture at 10 • C, it was decreased from 30,933 to 3948 cP by increasing the shear rate from 0.03 to 0.38 S −1 , respectively. Thermogravimetric analysis, differential scanning calorimeter and density measurements were all reported in detail in this paper.
Potential Application of Deep Eutectic Solvents in Heat Transfer Application
2017
Glycol based conventional fluids are generally used as coolants and antifreezing agents in industrial applications. Thus, this paper explores the possibility of utilizing DES as a heat transfer fluid due to their enhanced thermal stability compared to conventional fluids. Thermal conductivity of four types of DES comprising of methyl triphenyl-phosphonium-bromide (MTPB) and choline chloride (ChCl) as salts, and ethylene glycol (EG) and triethylene glycol (TEG) as the hydrogen bond donor (HBD), are measured from 25°C to 50°C using KD2 Pro thermal properties analyser. The obtained results show that the presence of salt lowers the thermal conductivity of the pure organic fluids. As the temperature increases, the thermal conductivity of the DESs increase compared to the thermal conductivity of pure organic solvents that does not change with temperaure. At higher temperature (50°C), the thermal conductivity decreased by 9.9% for MTPB:EG-DES, 5.4% for MTPB:TEGDES and 5.4% for ChCl:EG-DESs...
Physical properties of ethylene glycol-based deep eutectic solvents
Journal of Molecular Liquids, 2018
Deep eutectic solvents (DESs) have been widely recognized as ionic liquids (ILs) analogues due to their low production cost and superior favorable properties over conventional ILs. Studying the physical properties of these solvents will contribute to design processes involving DESs. In this study, five DESs have been successfully prepared using ethylene glycol (EG) as hydrogen bond donor (HBD) with N,N-diethylethanolammnium chloride (DAC), benzyltriphenylphosphonium chloride (BTPC), choline chloride (ChCl), methyltriphenylphosphonium bromide (MTPB) and tetra-n-butylammonium bromide (TBAB) as salts. The freezing point of each of the five studied DESs was measured using Differential Scanning Calorimetry (DSC) and the DESs functional groups were identified using the Fourier transform infrared (FTIR) spectroscopy. Moreover, the viscosity, density, electrical conductivity and surface tension were measured at a temperature range of 293.15-353.15 K and they were highly affected by the variation of the temperature. It is worth mentioning that
Journal of Chemical & Engineering Data, 2017
Deep eutectic solvents (DES) containing benzyl triethylammonium chloride (BTEAC) as a hydrogen bond acceptor (HBA) and p-toluene sulfonic acid (PTSA), citric acid (CA), and oxalic acid (OX) as a hydrogen bond donor (HBD) were formed at their respective eutectic points. The physical properties such as pH, ionic conductivity, viscosity, density, and refractive index were measured between 293 and 333 K. Viscosity values as low as 0.21 Pa•s and conductivity values as high as 8 mS/cm were achieved, where the pH values of each DES proved to be extremely low. The effect of HBD on the physical properties was investigated and was found to be very significant. Also, the catalytic application of BTEAC based DES in the esterification reaction of the acetic acid with 2-ethyl-hexanol was studied, and the activation energy was obtained using initial reaction rates. The results showed that very high initial reaction rates and low activation energy can be achieved when catalyzed by DES which was formed using BTEAC and PTSA.