Deep Depolymerization of Lignin via Reductive Acidolysis Yielding Copious Aromatics Thoroughly Revealed by NMR Chromatography.

Depolymerization is the cornerstone of lignin valorization. Although this field of research has advanced significantly in the past decade, there are still obstacles preventing large‐scale application. The high cost of precious metal catalysts and the use of pressurized hydrogen gas account for some of the limitations. In this work, it is designed to synergize the reductive acidolytic power of hydrogen iodide and the advantageous physicochemical properties of ionic liquids (ILs) as green solvents for the deep depolymerization of real lignin. The results showed that nearly 100% of model compounds were converted in the reaction medium comprising 1‐butyl‐3 methylimidazolium iodide ([Bmim]I) plus organic acids and a yield up to 81 wt% of depolymerized products of low molecular weights was achieved for real lignins. In addition, a detailed structural assignment of the products was made straightforward by nuclear magnetic resonance chromatography. The advantages of the [Bmim]I/organic acids demonstrated in this study are featured by mild reaction conditions, easy scalability, and cost‐effectiveness, paving the way toward the democratization of lignin‐derived products.

Study on physicochemical properties of hydroxyl-functionalized ionic liquids

Phenolic ionic liquids for the efficient and reversible capture of CO(2) were designed and prepared from phosphonium hydroxide and substituted phenols. The electron-withdrawing or electron-donating ability, position, and number of the substituents on the anion of these ionic liquids were correlated with the physicochemical properties of the ionic liquids. The results show that the stability, viscosity, and CO(2)-capturing ability of these ionic liquids were significantly affected by the substituents. Furthermore, the relationship between the decomposition temperature, the CO(2)-absorption capacity, and the basicity of these ionic liquids was quantitatively correlated and further rationalized by theoretical calculation. Indeed, these ionic liquids showed good stability, high absorption capacity, and low absorption enthalpy for CO(2) capture. This method, which tunes the physicochemical properties by making use of substituent effects in the anion of the ionic liquid, is important for the design of highly efficient and reversible methods for CO(2)-capture. This CO(2) capture process using diverse phenolic ionic liquids is a promising potential method for CO(2) absorption with both high absorption capacity and good reversibility.

The physicochemical properties (density, viscosity, and carbon dioxide solubility) of ionic liquids based on pyridinium, pyrrolidinium, and ammonium cations were studied at atmospheric pressure and as a function of temperature between (293 and 343) K. The influence of the inclusion of oxygen functional groups (hydroxyl and ester) in the cations was assessed by comparing their behavior with that of similar nonfunctionalized ionic liquids. We observed that the presence of oxygen groups does not affect the density significantly. The inclusion of an ester group in the alkyl-side chain of pyridinium or ammonium cations greatly increases the viscosity of bis(trifluoromethylsulfonyl)imide ionic liquids (5 times for pyridinium, 2 times for ammonium-based ionic liquids at 293 K), while the presence of hydroxyl groups only slightly increases their viscosity (16 % increase for ammonium at 293 K). Carbon dioxide solubilities are not significantly influenced by the introduction of oxygen functional groups in the catio...

A hybrid smart modeling approach for estimation of pure ionic liquids viscosity

Nowadays, density functional theory (DFT)-based high-throughput computational approach is becoming more efficient and, thus, attractive for finding advanced materials for electrochemical applications. In this work, we illustrate how theoretical models, computational methods, and informatics techniques can be put together to form a simple DFT-based throughput computational workflow for predicting physicochemical properties of room-temperature ionic liquids. The developed workflow has been used for screening a set of 48 ionic pairs and for analyzing the gathered data. The predicted relative electrochemical stabilities, ionic charges and dynamic properties of the investigated ionic liquids are discussed in the light of their potential practical applications.

The effects of water addition and temperature on some physicochemical properties of room temperature ionic liquids containing chromium chloride, choline chloride and water in the molar ratio of 1:2.5:x (where x = 6, 9, 12, 15 or 18) have been studied. The density, viscosity, surface tension and conductivity of the liquid mixtures were measured for the temperature range of 25 to 80 °C. Increasing both water content and temperature resulted in decreasing density, surface tension and viscosity and increasing electrical conductivity. The average void radii (hole sizes) for the liquid systems under study were calculated; they were in the range of 1.21 to 1.82 A. The average hole size was stated to grow with increasing both temperature and water content in the mixture. The variation of the average void radii correlates with the change in viscosity and conductivity. The activation energies of viscous flow and conductivity diminishes with increasing water content in the liquid mixture. There is a strong linear correlation between conductivity and fluidity which indicates that the conductivity of the ionic liquid mixtures is generally controlled by the ionic mobility. A moderate viscosity and higher conductivity of the Cr(III)-containing ionic liquids with extra-water addition (at x > 9) make them suitable for the development of chromium electrodeposition processes.

Ionic liquids (ILs) have unique physicochemical properties such as favorable solubility of organic and inorganic compounds, relatively high ionic conductivity, no measurable vapor pressure, high thermal stability, low flammability, etc. ILs are also promising liquid materials available for various applications because their function can be easily controlled by changing the combination of cations and anions and by introducing substituents. Although many kinds of ILs have already been investigated, phosphonium cation based ILs have rarely been proposed. We have previously designed and synthesized the phosphonium ILs together with typical sulfonylamide-based anions such as bis(trifluoromethylsulfonyl)amide and bis(fluorosulfonyl)amide anions.1,2) On the other hand, interests in phosphonium ILs consisting of the other anions is increasing for diverse applications. In this work, we design and prepare the ILs based on tetrabutylphosphonium cation (P4444 +) together with various sulfonate-based anions (Fig. 1), characterizing their physicochemical properties as a new family of ILs. The phosphonium IL was prepared by an aqueous neutralization reaction of tetrabutylphosphonium hydroxide with the stoichiometric amounts of various sulfonic acids. The obtained phosphonium ILs were isolated by water evaporation, and were dried in vacuo for at least 1 day. The physicochemical properties of ILs, e.g. density, viscosity, conductivity (ac impedance method) and thermal decomposition temperature (thermogravimetric analysis), were measured under argon atmosphere.The phosphonium salts based on unsubstituted sulfonate anions such as SO3CH3, SO3CH2CH3 and SO3(CH2)2CH3 were white crystalline solids at room temperature, whereas both amino- and hydroxy- substituted sulfonate salts were viscous liquids at room temperature. All phosphonium salts obtained were hydrophilic. Table 1 summarizes the physicochemical properties of phosphonium ILs based on amino- and hydroxy-substituted sulfonate anions. These phosphonium ILs exhibited considerably high viscosities when compared to the previously published viscosity value of P4444-lactate IL (415 mPa s at 25 °C)3), which suggests that the electrostatic interaction between P4444 cation and the sulfonate anions is much stronger than those in the case of carboxylate-based phosphonium ILs. It should be noted that P4444-SO3(CH2)3NH2 obviously indicated not only the highest density but also the highest viscosity and the lowest conductivity, which might be due to the fact that the IL has the largest anion to give a significant van der Waals interaction. Figure 1

Theoretical and experimental studies of ionic liquid-urea mixtures on chitosan dissolution: Effect of cationic structure

The purpose of this study was to determine the difficulties faced by pre-service chemistry teachers in correlating the structures with the physicochemical properties of ionic liquids. The descriptive research method used quantitative and qualitative approaches The participants in this study were 23 pre-service chemistry teachers from one of the universities in Indonesia. Data collected using an instrument in the form of a description test guided by the discourse on ionic liquid technology. In general, the results of the study indicate that more than half of the students have difficulties in applying chemical concepts related to the context of the relationship of structures with the physicochemical properties of ionic liquids. The result also reveals that the most dominant difficulty experienced by pre-service chemistry teachers is difficult to determine the right chemical concepts to explain the tendency of melting point differences of molten salt and ionic liquids. The results findings will be used as the basis for developing didactic designs that are oriented to resolve learning obstacles by pre-service chemistry teachers in understanding the relationship of structures with physicochemical properties of ionic liquids

In an attempt to produce new functionalized ionic liquids, a series of thiosalicylate ionic liquids based on imidazolium, ammonium, phosphonium, choline and pyrrolidinium cations were synthesized. The compounds were characterized by Infra Red (IR), Nuclear Magnetic Resonance (NMR) and mass spectra (ESI-MS). Their glass-transition temperatures, melting points and decomposition temperatures have been measured. Physicochemical properties of ionic liquids are influenced by alkyl chain length and nature of the cation of ionic liquids. A series of thiosalicylate ionic liquids based on imidazolium, ammonium, phosphonium, choline and pyrrolidinium cations were prepared. The compounds were characterized and their thermal properties were investigated. The physicochemical properties of ionic liquids are influenced by the alkyl chain length and the nature of the cation of ionic liquids.

Research since 2000 has clearly shown that ionic liquids (ILs) and their metal salt containing mixtures have good potential to be considered as electrolytes (ILELs) in lithium and other electropositive metal (ion) batteries. This outcome is particularly relevant for the operation of such devices in elevated temperature regimes where ILELs would have a significant advantage over the conventional organic carbonate solvent/LiPF6 electrolytes that, due to their limited thermal stability and flammability, cause concerns about the safety of current LIB technology. There is evidence from a number of review articles that physicochemical properties can be tailored such that ILELs could meet requirements for operating in batteries at lower temperature regimes. By drawing on a broad range of cation/anion combinations, there is further evidence from these papers that within a particular family of cations, the physicochemical properties of ILs and ILELs are largely defined by the anion component. Despite the key role of the anion there are few reviews that have sections dedicated to this aspect. This review surveys the physicochemical, transport and structural properties of ILs (mainly pyrrolidinium salts) and ILELs employing prominent and representative anion classes.

Determination of physicochemical properties of ionic liquids by gas chromatography

Investigation of the interionic interactions and spectroscopic features of 1-Octyl-3-methylimidazolium chloride, tetrafluoroborate, and hexafluorophosphate ionic liquids: An experimental survey and DFT modeling

An ionic liquid is a salt that has a melting point lower than the boiling point of water. Other names for ionic liquids include molten salts, designer solvents, neoteric solvents, and ionic fluids. Ionic liquids are mostly composed of inorganic anions and organic cations. This review looks at the many physicochemical properties of ionic liquids as well as some of their key features. The physicochemical characteristics and importance of ionic liquids are the main topics of this review