Ionic Liquid Solutions Research Articles

Application of silver ionic liquid in the separation of olefin and alkane

AbstractBACKGROUNDThe separation of olefins and alkanes remains one of the most challenging industrial processes due to their similar structure and boiling points. Traditional industrial methods are limited as a consequence of high equipment cost and energy consumption. Ionic liquids (ILs) for olefin separation systems have been developed in recent years. This study aimed to synthesize silver (Ag+) IL and apply it in both extraction and membrane processes to enhance the separation performance.RESULTSQuantum chemical calculation results show that the interaction energy between the IL and cyclohexene is much larger than the values for interactions between the IL and alkanes. The highest selectivities for cyclohexene in the extraction process were 33.4 and 51.9 in the presence of cyclohexane and hexane, respectively. The gel membrane was prepared by casting a mixture of 12HSA and Ag+ IL solution onto the PVDF membrane. In vapor permeation, high separation performance was obtained together with a stable membrane phase when the 12HSA content was 1.50% and the operating temperature was 45 °C. With the increase of the mole fraction of cyclohexene, the permeation flux gradually increased and the separation factor was maintained at >9.CONCLUSIONReversible π‐complex formation between Ag+ ions and cyclohexene can effectively enhance the separation performance in both extraction and membrane process. This study presents a promising alternative to conventional technology for olefin and alkane separations. © 2021 Society of Chemical Industry (SCI).

A thermodynamic framework for determination of gas hydrate stability conditions and water activity in ionic liquid aqueous solution

The formation of gas hydrates in pipelines and plugging of the gas flow path are a major cause of operating expenses, safety issues, pressure drop, and fatal accidents. Therefore, the inhibition of gas hydrate formation is of paramount importance. The utilization of a new class of inhibitors such as ionic liquids (ILs) is currently of great interest. In this regard, adjusting water activity in the inhibitor blend (water + IL) is a vital factor. Several models have been developed to calculate the activity of water in the presence of IL(s). The major disadvantage of these models is their correlative basis. This study aimed to propose a rigorous predictive model for the calculation of water activity in the presence of IL(s), which would then be applied in the prediction of the gas hydrate stability conditions. The model is made up of a molecular term (the short-range interactions from Free-Volume-Flory-Huggins (FVFH) activity model) as well as a contribution from ionic interactions as a result of IL(s) dissociation in water (the long-range electrostatic interactions from the extended Debye–Hückel (EDH) model). The overall absolute temperature deviation and the average absolute relative deviation percent in the calculated gas (methane and carbon dioxide) hydrate dissociation temperatures for the whole databank (500 data points including 37 ILs) were found to be 0.61 K and 0.22%, respectively. This proves the superiority of the model over the previous correlative-basis ones. Finally, it is concluded that the higher temperature, the higher the IL(s) concentration, and the lower IL(s) molecular weight(s) result in larger model deviations.

Chlorophylls Extraction from Spinach Leaves Using Aqueous Solutions of Surface-Active Ionic Liquids

Chlorophylls and their derivatives have been extensively studied due to their unique and valuable properties, including their anti-mutagenic and anti-carcinogenic features. Nevertheless, high-purity-level chlorophylls extracted from natural sources are quite expensive because the methods used for their extraction have low selectivity and result in low yields. This study aimed to develop a “greener” and cost-effective technology for the extraction of chlorophylls from biomass using aqueous solutions of ionic liquids (ILs). Several aqueous solutions of ILs, with hydrotropic and surface-active effects were evaluated, demonstrating that aqueous solutions of surface-active ILs are enhanced solvents for the extraction of chlorophylls from spinach leaves. Operating conditions, such as the IL concentration and solid–liquid ratio, were optimized by a response surface methodology. Outstanding extraction yields (0.104 and 0.022 wt.% for chlorophyll a and b, respectively, obtained simultaneously) and selectivity (chlorophyll a/b ratio of 4.79) were obtained with aqueous solutions of hexadecylpyridinium chloride ([C16py]Cl) at moderate conditions of temperature and time. These extraction yields are similar to those obtained with pure ethanol. However, the chlorophyll a/b ratio achieved with the IL aqueous solution is higher than with pure ethanol (3.92), reinforcing the higher selectivity afforded by IL aqueous solutions as viable replacements to volatile organic compounds and allowing the obtainment of more pure compounds. Finally, the recovery and reuse of the solvent were evaluated by using a back-extraction step of chlorophylls using ethyl acetate. The results disclosed here bring new perspectives into the design of new approaches for the selective extraction of chlorophylls from biomass using aqueous solutions of surface-active ILs.

On the prediction of thermo‐physicochemical properties and equilibrium absorption of CO 2 into aqueous protic monoethanolamine glycinate ionic liquid

The utilization of pure ionic liquids (ILs), as environmentally green and soft chemical solvents, is restricted in the CO2 capture industry due to their high viscosity and fair conductivity. In this paper, the novel comprehensive models were developed for accurate estimation of density, dynamic viscosity, surface tension, and electrical conductivity of a novel protic amino acid-functionalized IL, namely monoethanolamine glycinate, [MEA][GLY], in the temperature range of 303.15–323.15 K at two different intervals of water content (5–20 wt%, and 25–100 wt%). The results of the suggested models revealed that the density, viscosity, and surface tension of [MEA][GLY] decline substantially with rising temperature, while the electrical conductivity presents an adverse trend. Additionally, the impact of varying the concentration on the density and viscosity of the IL solution is more significant than the solution temperature, particularly at high concentrations of the IL. Moreover, a second-order polynomial equation was suggested to depict the equilibrium pressure dependence of CO2 loading capacity of aqueous [MEA][GLY] in IL, at various equilibrium pressures of 1–7 bar.

Ultrasonic-assisted extraction of zeaxanthin from Lycium barbarum L. with composite solvent containing ionic liquid: Experimental and theoretical research

Zeaxanthin is the main active ingredient of Lycium barbarum L. The current extraction methods of zeaxanthin are not only tedious and time-consuming but also environmentally unfriendly. Therefore, in the present study, an efficient simultaneous extraction and saponification method for extracting zeaxanthin from L. barbarum was established by using the composite solvent composed of ionic liquid (IL), ethanol, and inorganic base with the assistance of ultrasonic waves. The yield of zeaxanthin was evaluated by high-performance liquid chromatography (HPLC). The optimal ionic liquid, [Hmim][OAc], was selected by combining experimental research with quantum chemical calculation. The extraction mechanism was investigated by quantum chemical calculations combined with density functional theory (DFT), atoms in molecules (AIM) and reduced density gradient (RDG) analyses, and the hydrogen bonds and van der Waals interactions between zeaxanthin and ILs were the main driving forces for ionic liquid extraction. The extraction conditions were optimized using single-factor and response surface methodology as follows: KOH concentration of 6.3%, ionic liquids concentration of 0.09 g/mL, ultrasonic treatment time of 39 min, solid-liquid ratio of 1:40, and the ultrasonic power of 420 W. Compared with the traditional extraction method, the newly established method improved the extraction yield by 23.08% and shortened the extracting time by 90%. Meanwhile, high purity of zeaxanthin could be easily recovered from the ILs solution.

Physicochemical properties and the molar surface Gibbs energy of the aqueous solution of amino acids ionic liquid 1-pentyl-3-methylimidazolium glycine salt [C5mim] [Gly

The density and surface tension for the aqueous solution of amino acids ionic liquid (AAIL) 1-pentyl-3-methylimidazolium glycinate salt [C5mim] [Gly] with various molalities were measured at T = (288.15 to 318.15) K with an interval of T = 5 K, and based on the experimental values, the molar surface Gibbs energy of the ionic liquid solution was obtained, in addition, the relationship between the molar surface Gibbs energy and molalities was explored.

Efficient and reversible CO2 capture in bio-based ionic liquids solutions

Choline/amino acid-based ionic liquids were synthetized via ionic metathesis and their CO2 absorption performances evaluated by employing different experimental approaches. In order to overcome any viscosity-related problem, dimethyl sulfoxide (DMSO) was employed as solvent. IL-DMSO solutions with different IL concentrations were evaluated as absorbents for CO2, also investigating their good cyclability as desirable for real industrial CO2 capture technologies. 1H-NMR and in-situ ATR-IR experiments were the toolbox to study the CO2 chemical fixation mechanism under different experimental conditions, proving the formation of distinct chemical species (carbamic acid and/or ammonium carbamate). In general, these ILs demonstrated molar uptakes higher than classical 0.5 mol CO2/mol IL and the capacity to release CO2 in extremely mild conditions. The possible biological adverse effects were also analyzed, for the first time, in zebrafish (Danio rerio) during the development, by assessing for different toxicological endpoints, proving the non-toxicity and high biocompatibility of these bio-inspired ILs.

Ionic Liquids and Water: Hydrophobicity vs. Hydrophilicity.

Many chemical processes rely extensively on organic solvents posing safety and environmental concerns. For a successful transfer of some of those chemical processes and reactions to aqueous media, agents acting as solubilizers, or phase-modifiers, are of central importance. In the present work, the structure of aqueous solutions of several ionic liquid systems capable of forming multiple solubilizing environments were modeled by molecular dynamics simulations. The effect of small aliphatic chains on solutions of hydrophobic 1-alkyl-3-methylimidazolium bis(trifluoromethyl)sulfonylimide ionic liquids (with alkyl = propyl [C3C1im][NTf2], butyl [C4C1im][NTf2] and isobutyl [iC4C1im][NTf2]) are covered first. Next, we focus on the interactions of sulphonate- and carboxylate-based anions with different hydrogenated and perfluorinated alkyl side chains in solutions of [C2C1im][CnF2n+1SO3], [C2C1im][CnH2n+1SO3], [C2C1im][CF3CO2] and [C2C1im][CH3CO2] (n = 1, 4, 8). The last system considered is an ionic liquid completely miscible with water that combines the cation N-methyl-N,N,N-tris(2-hydroxyethyl)ammonium [N1 2OH 2OH 2OH]+, with high hydrogen-bonding capability, and the hydrophobic anion [NTf2]–. The interplay between short- and long-range interactions, clustering of alkyl and perfluoroalkyl tails, and hydrogen bonding enables a wealth of possibilities in tailoring an ionic liquid solution according to the needs.

Suspended particles behavior in aqueous [Bmim]BF4 solution by novel on-line electrical sensing zone method

Ionic liquids (ILs) and aqueous ionic liquid solutions have been investigated as excellent solvents or catalysts in a few multiphase systems. To optimize the reactor design and operation conditions, it is significant to study the suspended particles behaviors in ILs involved solid–liquid mixing processes. A novel on-line electrical sensing zone (ESZ) method is developed to achieve the measurement of local solids concentration in aqueous [Bmim]BF4 conductive solutions. The suspension degrees of solid particles stirred by different impellers at varied agitation speeds have been obtained. The mean fluid velocities and turbulent fluctuating velocities close to the bottom of the unbaffled tanks have been determined by stereoscopic particle image velocimetry (SPIV). The results showed that the aqueous [Bmim]BF4 solutions are more efficient on solids than normal saline solution. Radical flow impeller with wider blades at C/T = 0.2 presents its better performance on solids suspension. The variations of solids suspension curves are more consistent with that of mean radial velocities at axial height of z/H = 0.99. It indicated that the solids suspension in unbaffled stirred tanks is mainly related to the mean flow rather than to turbulent fluctuations.

Effect of alkyl chain length and temperature on volumetric, acoustic and apparent molar properties of pyrrolidinium based ionic liquids in acetonitrile

Detailed analysis of volumetric and acoustic properties of the dilute solution of ionic liquids (ILs) and acetonitrile play a significant role in the potential engineering field and process design. Moreover, these studies can provide relevant knowledge about the types and scope of the intermolecular interactions governed between the solute and solvent. In this work, three iodide based pyrolidium ILs, i.e. 1-butyl-1-methyl pyrrolidinium iodide, [BMPY]I and 1-methyl-1-pentyl pyrrolidinium iodide, [PeMPY]I and 1-hexyl-1-methyl pyrrolidinium iodide, [HMPY]I were synthesized and studied their density and sound velocity in acetonitrile as a function of molality in the range of 0.05–0.4 mol·kg−1 and temperature in the range from 293.15 to 328.15 K at atmospheric pressure. The impact of chain length of cation and temperature were premeditated by using well-known volumetric and acoustic factors. In addition, by employing the experimental data, the apparent molar volume (Vϕ), apparent molar isentropic compression (Ks,ϕ), and limiting apparent molar expansion (Eφ∞) were calculated. Further, the apparent molar properties at infinite dilution were examined by using Redlich-Mayer type equations. Furthermore, measured and calculated properties have been analysed to understand the solute-solvent interaction in studied systems. For the studied systems, infinite dilution apparent molar properties were increased with cationic chain length on the ILs, however, decreased with temperature.

Removal of Pyridine, Quinoline, and Aniline from Oil by Extraction with Aqueous Solution of (Hydroxy)quinolinium and Benzothiazolium Ionic Liquids in Various Ways

Based on above background, quinolinium, 8-hydroxy-quinolinium, and benzothiazolium ionic liquids, containing the acidic anions of methanesulfonate ([CH3SO3]−), phosphate ([H2PO4]−), p-toluenesulfonate ([p-TSA]−), and bisulfate ([HSO4]−) were synthesized. After comparison, the aqueous solution of benzothiazole bisulfate [HBth][HSO4] was selected as the most ideal extractant for removing pyridine and aniline. Meanwhile, benzothiazole bisulfate [HBth][HSO4] solution was found as the best one for removing quinoline from simulated oil. Then, the single stage extraction and two-step extraction were used in the extraction for the simulated oil containing pyridine, quinoline or aniline, and their mixture, respectively. Their denitrogenation performance on their N-removal effect was compared on the basis of structural features, and main extraction conditions were further investigated, including mass ratio of IL to water, mass ratio of IL to oil, and temperature. Furthermore, the extraction process was described by two kinetic equations. Recovery and reuse of IL were realized by back-extraction and liquid-liquid separation, and a related mechanism was speculated, according to all the experimental results. Finally, based on the developed method for preparing complex adsorbent tablets, corresponding immobilized IL was used to remove target objects, by solid phase extraction, in order to extend separation ways, which was more easily recovered after extraction.

Enhancing the interaction between cellulose and dilute aqueous ionic liquid solutions and its implication to ionic liquid recycling and reuse

Cellulose-dissolving ionic liquids (ILs) have been used in biomass pretreatment for over a decade. Cellulose solubility in the ILs is strongly inhibited by water, which has negative impacts on IL pretreatment and reuse of the recycled ILs. Here, a distillation and aeration apparatus was used as the reactor for biomass pretreatment in dilute aqueous IL solutions and in recycled IL liquor without drying or purification. Four biomass types, switchgrass, miscanthus, sorghum and pine, were studied. X-ray diffraction (XRD) was used to measure the interaction between biomass and the IL. Small angle neutron scattering (SANS) was applied to monitor the changes of the pore structure in wet biomass samples. Satisfactory enzymatic hydrolysis results were obtained among all the pretreated samples.

Removing CO2 from Xenon anaesthesia circuits using an amino-acid ionic liquid solution in a membrane contactor

• System capacity increased from 3.50 to 4.97 mol CO 2 /kg IL when breathing cycles were simulated. • Higher amount of anaesthetic gas can be recycled when Xe is used. • Ion-exchange allows for releasing CO 2 enabling the reuse of the IL solution. The noble gas xenon possesses many characteristics of an ideal anaesthetic agent. However, its application is limited in daily clinical routine due to its elevated price. The present work proposes the use of a gas-ionic liquid membrane contactor system in anaesthesia closed-circuits, for the removal of carbon dioxide, to allow the recycling of the anaesthetic agents, as a route to enable the widespread use of xenon. In this work, different anaesthetic gas delivery conditions were simulated and explored, considering the use of different anaesthetic gas mixtures. The results obtained, using a cholinium lysinate ionic liquid solution as CO 2 absorbent, expressed high efficiency, especially when xenon was used as the inhalational anaesthetic, leading to an overall CO 2 mass transfer of 1.26 × 10 −5 m.s −1 . The ability of the proposed system to recover xenon allows to reduce drastically the cost per operation, which can be a step forward for the routine use of this gas on surgeries. Additionally, this work evaluates the use of thermal and chemical regeneration of the ionic liquid solution. It was found that the thermal regeneration approach was not adequate for the regeneration of the IL. On the other hand, the use of ion-exchange resins proved to be an efficient and simple strategy for IL regeneration, allowing for an easy integration in the proposed system. This study opens a new direction not yet explored that may lead to more efficient IL regeneration processes.

Effect of temperature on the osmotic behavior of LCST type ionic liquid solutions as draw solutions in the forward osmosis process

In this work, several types of ionic liquid (IL)-based thermosensitive draw solutions (DSs) were prepared for application in the forward osmosis (FO) process. The temperature dependence of the osmotic pressure of IL-based DS was investigated to examine the advantages of high-temperature membrane operation for regeneration and water recovery from the DS lean phase after liquid–liquid phase separation of DS with a lower critical solution temperature (LCST). From surface tension and dynamic light scattering measurements, it was found that the association of IL molecules and aggregation of IL associates occurred in hot water, which led to a decrease in the osmotic pressure of the IL-DS at elevated temperatures. The DS regeneration and water recovery using an RO membrane were examined using tetrabutylammonium 2,4,6-trimethylbenzenesulfonate with the largest temperature dependence on osmotic pressure. At elevated temperatures, the water flux and DS concentration in the concentrated solution increased effectively. The investigation demonstrated that high-temperature membrane operation is effective for the regeneration of LCST-type thermosensitive DS and water recovery.

Imidazolium-based poly(ionic liquid)/ionic liquid solutions: Rheology, structuration and ionic transport properties

RAFT-made poly(ionic liquid) chains (PIL), poly(1-[2-acryloylethyl]-3-methylimidazolium bromide) (Poly [AEmim][Br]), have been mixed with a ionic liquid (IL), namely butylmethylimidazolium chloride ([C4mim][Cl].) The similarities in terms of structure and polarity of these molecular and macromolecular imidazolium derivatives led to homogeneous and transparent solutions. The influence of the chain molar mass and the concentration was examined through rheology investigation. It was established that the steady-shear viscosity of the solutions, and the viscoelastic properties can be finely tuned by these two parameters and by temperature. The thermal-dependence of the rheological features allowed for determining high activation energies (Ea) (around 80 kJ/mol), compared to analogous PIL aqueous solutions. Such Ea values reflect high cohesion in PIL/IL solutions, related to the formation of multiple strong interactions, such as hydrogen bonds, van der Waals forces and Coulomb interactions between ionic species. Wide-angle and small-angle X-ray scattering experiments as well as scanning electron microscopy analysis evidenced a multi-scale local homogeneity of the PIL/IL solutions, which additionally exhibit high ionic conductivity (ca. 10−3 S/cm at 30 °C), as measured by broadband dielectric spectroscopy.

How Temperature, Pressure, and Salt Concentration Affect Correlations in LiTFSI/EMIM-TFSI Electrolytes: A Molecular Dynamics Study.

Classical polarizable molecular dynamics simulations have been performed for LiTFSI solutions in the EMIM-TFSI ionic liquid. Different temperature or pressure values and salt concentrations have been examined. The structure and dynamics of the solvation shell of Li+ cations, diffusion coefficients of ions, conductivities of the electrolytes, and correlations between motions of ions have been analyzed. The results indicated that regardless of the conditions, significant correlations are present in all systems. The degree of correlations depends mainly on the salt fraction in the electrolyte and is much less affected by temperature and pressure changes. A positive correlation between motions of Li+ cations and TFSI anions, leading to the occurrence of negative Li+ transference numbers, exists for all conditions, although temperature and pressure changes affect the speed of anion exchange in Li+ solvation shells.

Extraction of Essential Oil from Black Pepper (Piper nigrum) by using Ionic Liquid Solution (Acetic acid and Glucose Solution)

Essential oils fall among the volatile class of plant bioactive compounds and progressively used in food, fragrance, cosmetic and pharmaceutical industries. A great deal of research has been devoted to the extraction of essential oils from plant sources for extraction of important compounds. The present research deals with extraction of essential oil from black pepper (Piper nigrum L.) by using ionic liquids solution. Piper nigrum L. was collected from local market of Lahore, ground to fine powder and processed via hydro distillation using Clevenger tube. Extraction yield was optimized by changing process parameters including incubation time, ionic liquid composition, quantity of acetic acid (ml) and glucose conc. (ml) and liquid to solid (L/S) ratio. The influence of process variables was investigated, tested and optimized using response surface methodology using Design Expert 7.0.0 software. The maximum yield was noted 2.56 % corresponding to conditions: acetic acid 25-35ml, glucose 65-75ml, incubation time of 4-5h and L/S ratio of 5-6. The study concluded that yield of essential oil can significantly be increased by using ionic liquids solution at low temperature.

Controllable superlubricity achieved with mixtures of green ionic liquid and glycerol aqueous solution via humidity

In this work, superlubricity between steel surfaces lubricated by mixtures of [Choline][Proline] ([Cho][Pro]) ionic liquid and glycerol aqueous solution has been reached by using a rotating tribometer. Stable superlubricity could be obtained even under the humidity between 7 and 9% RH. The lowest friction is observed when the lubricant contains 3 wt% ionic liquid. It is found that adding 3 wt% [Cho][Pro] is helpful to maintain enough water in the steady period to retain a low viscosity. According to the calculation, the superlubricity achieved in thin film lubrication region, which is attributed to the stern layer formed by [Cho][Pro] and hydrogen-bond network that enabled a thin water layer at the interface. Interestingly, it is observed that humidity can be used to control lubrication state between superlubricity and non-superlubricity. This study provides a new method to accomplish switchable superlubricity under low humidity.

Rheological study of microcrystalline cellulose/pyridinium-based ionic liquids solutions

Rheological study of microcrystalline cellulose/pyridinium-based ionic liquids solutions

Rational design of ultrathin composite solid-state electrolyte for high-performance lithium metal batteries

To address the safety and low energy density of conventional liquid electrolyte lithium-ion batteries, ultrathin solid-state electrolyte with high mechanical modulus and ionic conductivity has been widely concerned. Here, we report an ultrathin, mechanically robust and flexible composite solid-state electrolyte, composed of three-dimensional network host (polyimide (PI) film), ionic conductive inorganic particle (Li6.75La3Zr1.75Ta0.25O12), polymer binder (polyvinylidene fluoride), and lithium salt-ionic liquid solution. PI film guarantees the flexibility and thin thickness (∼25 μm) of the composite electrolyte. The introduction of high-content ceramic filler and ionic liquid enhance mechanical strength and room-temperature ionic conductivity (3.7 × 10−4 S cm−1) of composite electrolyte while reducing the interfacial impedance between the electrolyte and the electrode. The capacity retention (153 mAh g−1) of the LiNi0.5Co0.2Mn0.3O2|Li battery based on the prepared electrolyte is 88% after 100 cycles at 0.1C, which has high safety in practical applications.