Ionic Liquid Solutions Research Articles

Subsistence of diverse interactions of some biologically important molecules in aqueous ionic liquid solutions at various temperatures by experimental and theoretical investigation

To investigate significant molecular interactions, different Physico-chemical methodologies have been studied and measured for mixtures of aqueous Benzyltriethylammonium chloride with two amino acids (L-Cysteine and Glycine) at various concentrations and temperatures under atmospheric pressure. The origin of various interactions is exposed by evaluating the apparent molar volume (ϕV), limiting apparent molar volume (ϕV0), viscosity A and Bcoefficients, molar refraction (RM), limiting molar refraction (RM0), and detected strong solute-solvent interaction is predominating over the solute-solute and also solvent-solvent interactions in the ternary mixtures. The solute-solvent interaction is measured through (δϕE0/δT)P and (dB/dT) data which provide information like structure-breaking. The findings of 1H NMR spectroscopy show that, in addition to H-bonding interactions, the ionic liquid and amino acids have significant hydrophobic-hydrophobic interactions, which is confirmed by theoretical explanations. L-Cysteine-IL interactions are more prominent than Glycine-IL interactions, according to both experiment and theory.

Molecular Interactions of Some Bioactive Molecules Prevalent in Aqueous Ionic Liquid Solutions at Different Temperatures Investigated by Experimental and Computational Contrivance

The solute –solvent interaction between ionic liquids (ILs) and amino acids (AA) in aqueous media plays a significant role for the optimization of a number of important biotechnological processes. l-Valine and l-Proline (two solute molecules) interact with an ionic liquid (Benzyltributylammonium chloride) in aqueous medium. Based on the different parameters such as apparent molar volume, viscosity B-coefficient, molar refraction, molar conductance at different temperatures and different concentrations from density, viscosity, refractive index, conductance measurements have been used to explain the molecular level interactions which was supported by NMR and UV–Vis studies. Using Masson equation, the experimental slopes and the limiting apparent molar volumes are obtained which explain the solute-solute and solute-solvent interactions. Hepler's technique and dB/dT values have been used to examine the structure-making and structure-breaking nature of the solutes in the solvents. Viscosity parameters, A and B obtained from Jones-Doles equation explained the solute-solute and solute-solvent interactions in the solution. Lorentz-Lorenz equation has used to calculate the molar refraction. The specific conductance also explained the interaction properties. Further the findings have been supported by NMR study of the solutions and also considerable amount of theoretical analysis has been done which was in good agreement with the experimental result. The behavior of many other bio-molecules can be explained by considering amino acids as model and the mechanism has been extended to elucidate the behavior of other (biological) systems. In our findings we were emphasized on the nature of solute–solvent interactions and the presence of structural effect on the solvent in solution to analyze the molecular-level interactions prevalent in the systems.

Physico-chemical characterization of aqueous solutions of superbase ionic liquids with cellulose dissolution capability

Superbase-based ionic liquids 7-methyl-1,5,7-triazabicyclo[4.4.0]dec‑5-enium acetate, [mTBDH][OAc], and 5-methyl-1,5,7-triaza-bicyclo[4.3.0]non-6-enium acetate, [mTBNH][OAc], are good candidates to produce high performance cellulose fibres while presenting much easy spinnability and good recyclability, than the state-of-the-art ionic liquids. Nevertheless, the recovery of the IL from the aqueous spinning bath and its purification, which are both an economical and environmental necessity, are important aspects that are still not solved. Aiming to gather knowledge to recover and recycle superbase-ILs, the main goal of this work is the physicochemical characterization of the binary systems water + [mTBDH][OAc] or [mTBNH][OAc]. Measurements performed include solid-liquid equilibria, vapor-liquid equilibria, water activity, Kamlet−Taft solvatochromic parameters, densities, and viscosities. An experimental screening on possible hydrophobic extractants for the recuperation of the ionic liquids from aqueous solution was performed. Using butanol, an extraction efficiency of 37% for [mTBDH][OAc] was achieved. Better extraction efficiencies were achieved with chlorinated solvents, however, they seem to react with the ILs anion.

Non-dispersive solvent absorption of post-combustion CO2 in membrane contactors using ionic liquids

Post-combustion carbon-capturing (PCC) is one of the technologies that has been expanded in recent years, to control greenhouse gas emissions. This work aims to explore the potential applications of polymeric hydrophobic membranes and green ionic liquids (ILs). Experiments were conducted on lab-scale flat sheet (FS) membrane contactors (MCs) where CO2 was captured from a continuous feed mixture (CO2 + N2) with a recirculated-based aqueous solution of IL at a constant temperature of 298 K and with no pressure driving force. The effects of contact angle, liquid entry pressure (LEP), initial CO2 concentration, and type of solvents and membrane material on the CO2 capture efficiency and membrane wetting in the PCC process have been experimentally investigated and evaluated. Polytetrafluoroethylene (PTFE) has shown the most hydrophobic property with 6–17O loss in the contact angle. Furthermore, 1-Methyl-3-octyl-imidazolium-tetrafluoroborate ([OMIM][BF4]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF6]) have exhibited only 5–8 % loss in LEP using PTFE membrane support. The CO2 capture efficiency has been achieved as 80.8–99.8 % in different combinations of ILs and membrane support keeping all other variables constant. While increasing CO2 concentration from 15 to 45 % vol., an increase of nearly three folds in the CO2 mass transfer flux was observed. Combination of [OMIM][BF4] and PTFE membrane witnessed good long-term stability with only 20 % loss in CO2 capture efficiency in 480 min of continuous operation.

Electrochemical, thermodynamic, and physical properties of tetradecyltrihexylphosphonium ([P6,6, 6,14]+) and methyl-propyl piperidinium containing ionic liquids and their propylene carbonate solutions

The viscosity, conductivity, electrochemical window and related thermodynamic properties such as excess volume and dynamic viscosity deviation of two phosphonium ionic liquids were measured and calculated for “as-supplied” and dried neat liquids and also v/v mixtures of 99/1, 95/5, 90/10, 75/25, and 50/50 of the ionic liquids with propylene carbonate (PC). Tetradecyltrihexylphosphonium dicyanamide ([P6,6,6,14]+dicyanamide), Cyphos 105, and tetradecyltrihexylphosphonium bis(trifluororomethanesulfonyl)imide (called bistriflimide) ([P6,6,6,14]+bistriflimide), Cyphos 109, ionic liquids were studied. Generally speaking, there were slight differences in the measured properties of the wet and dried IL solutions which were reflected in differences if the calculated properties. The measured and calculated properties were compared with those collected and derived from a piperidinium-based ionic liquid, methyl-propyl piperidinium bistriflimide. Arrhenius plots for both the viscosity and conductivity were linear, with the linearity of the Litovitz plots being slightly higher. The viscosity and conductivity of the phosphonium solutions yielded Walden Plots that differed from Walden plots of piperidinium solutions and other ionic liquid solutions. For the phosphonium based ionic liquids, the ionicity was found to increase with increasing dilution in propylene carbonate. The electrochemical windows of the ionic liquids were determined as a function of the concentration of the ionic liquid present in the solution. The size of the window generally initially decreased and then increased with the addition of PC for the [P6,6,6,14]+dicyanamide ionic liquid increasing from 3.4 V in the 95/5 v/v (volume Cyphos 105) to volume of PC solvent) to 3.7 in the 50/50 dried IL case. The electrochemical windows of the dried liquids were slightly larger 3.5 V for the 95/5 v/v and 4.2 V for the 50/50 v/v Cyphos 105/PC solutions. The electrochemical window was larger and the conductivity was higher for the piperidinium IL solutions, but since the ionicity increases with dilution, the phosphonium based IL solutions may prove favorable for processes such as electrochemical reduction.

Surface modification of carbon fiber with imidazolium ionic liquids

ABSTRACT Carbon fiber composites are high-performance materials commonly used in advanced applications and their performance is highly dependent on the fiber-matrix interfacial interaction. The non-polar carbon fiber surface may be modified via different techniques to improve adhesion with the polymer matrix. In this work, non-covalent surface modification of carbon fiber has been carried out using two different imidazolium ionic liquids, 1-n-butyl-3-methyl imidazolium bis(trifluoromethylsulfonyl) imide (hydrophobic) and 1-n-butyl-3-methylimidazolium chloride (hydrophilic). The treatment was performed by immersing the fiber into 10 wt. % methanolic ionic liquid solution for 10 min. Treated fibers were characterized using Fourier-transform infrared spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy confirmed the presence of ionic liquid on the carbon fiber surface. Surface morphology of treated fibers analyzed by scanning electron microscopy showed ionic liquid moieties. Wettability of the treated carbon fiber with epoxy resin significantly increased, with a decrease in contact angle greater than 15°. Interfacial shear strength between the modified carbon fiber and epoxy increased up to 56.5% with respect to the unsized carbon fiber, being comparable with epoxy-sized fibers. Thus, the proposed surface modification has the potential to improve the interfacial performance of carbon fiber polymer composites.

Effect of imidazolium-based ionic liquids on the pore wetting characteristics and mechanical properties of coal

Exploring the pore wetting pattern of the imidazolium-based ionic liquids-water system is necessary to understand the dust reduction effect from the source of the coal seam and its influence on the mechanical properties. Low-field nuclear magnetic resonance (LF-NMR) is used to analyze the wetting effect of different concentrations and types of ionic liquids-water systems on different pore sizes from the pore size distribution. Uniaxial compression mechanics experiments are used to investigate the changes in mechanical properties of the coal after wetting, and a scanning electron microscope is used to observe the differences in surface morphology of the coal after treatment with aqueous solutions of ionic liquids. The results show that the wetting effect of aqueous solutions of different concentrations of imidazolium-based ionic liquids is different for micropores, mesopores and macropores compared to pure aqueous solutions. At the same time, the pore wetting of the coal samples by the aqueous solution of the imidazolium-based ionic liquids altered their mechanical properties, with a minimum strength of 8.57 MPa for the 2 wt% [Bmim][BF4] treated coal samples. Analysis of microscopic morphology shows that the surface minerals of coal samples treated with imidazolium-based ionic liquids are dissolved, forming linked fissures or pores between minerals, which positively affect pore wetting. The revelation of the pore wetting properties of ionic liquids systems on coal is conducive to enriching the theory of coal seam dust control and is of practical significance for efficient dust reduction in mines.

Thermodynamics and kinetics of novel amino functionalized ionic liquid organic solvent for CO2 capture

The main disadvantage of commercial absorption solution for CO2 capture from flue gas is extensive energy consumption. A novel amino-functionalized ionic liquid (AFIL) organic solution of tetraethylene pentamine 2-methylimidazolium/N-propanol/ethylene glycol ([TEPAH][2-MI]/NPA/EG) is considered as a promising candidate absorption system because of its efficient CO2 capture performance and low energy consumption. The thermodynamics and kinetics studies are very essential for evaluating the absorbent and its potential of future practical industrial application. In this work, the performance in these two aspects of [TEPAH][2-MI]/NPA/EG solution were investigated. The regeneration energy consumption was 2.98 GJ·t−1 CO2, which was 21.6% lower than that of benchmark monoethanolamine (MEA) aqueous solution, and the energy saving advantage was embodied in sensible heat and latent heat. Kinetic analysis showed that chemical reaction of CO2 absorption into [TEPAH][2-MI]/NPA/EG solution took place in the pseudo-first-order reaction. The reaction rate constant and enhancement factor increased with the increase of absorption temperature, while those showed a decreasing trend with the increase of absorption loading. The relation between the second-order rate constant and temperature was expressed as k2=5.6192×108exp-3111.6T, and the activation energy was further calculated as 25.87 kJ·mol−1. Compared with those of MEA and several traditional ionic liquid solutions, these parameters indicated a stronger reaction ability of the novel system. Moreover, the mass transfer resistance of gas and liquid phase changed constantly during the absorption process, and the dominant role of mass transfer resistance gradually changed from the gas phase to liquid phase. The thermodynamics and kinetics of CO2 capture revealed that the [TEPAH][2-MI]/NPA/EG solution had an excellent application potential in the future.

Intermolecular interactions between imidazolium- and cholinium-based ionic liquids and lysozyme: Regularities and peculiarities

The intermolecular interactions of imidazolium- and cholinium-based ionic liquids and hen egg-white lysozyme (HEWL) were studied by spectral, thermodynamic, and computational methods. The cholinium- and imidazolium-based ionic liquids: choline chloride [Ch][Cl], choline dihydrogenphosphate [Ch][DHP], choline acetate [Ch][OAc], 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4], 1-butyl-3-methylimidazolium trifluoromethanesulfonate [BMIM][TfO], 1-butyl-3-methylimidazolium acetate [BMIM][OAc] and 1-butyl-3-methylimidazolium methanesulfonate [BMIM][CH3SO3] were selected. The proton donor and acceptor abilities of ionic liquids were determined based on gas chromatography and solution calorimetry data. The temperature denaturation of HEWL in ionic-liquid solution was observed using capillary differential scanning calorimetry (DSC) and circular dichroism spectroscopy (CD). The interaction of ionic liquids with HEWL at the standard temperature was accessed by monitoring the protein’s fluorescence changes. The effect of the ionic liquid on the stability of the native structure of HEWL strongly depends on the proton acceptor ability of ionic liquids. The denaturation temperature of the native structure HEWL is linearly correlated with the enthalpy of the specific interaction (hydrogen bonding) of methanol and trichloromethane in the studied ionic liquids. At the same time, fluorescence data revealed ionic liquid-specific effects, which depend on both ions in the ionic liquid. Both fluorescence and molecular docking data indicate a lack of strong binding between the studied ionic liquids and HEWL.

Rheological scaling of ionic-liquid-based polyelectrolytes in ionic liquid solutions: the effect of the ion diameter of ionic liquids.

We investigate the effect of the ion diameter a of ionic liquids (ILs) on the shear viscosity of polymerized ionic liquids (PILs) in IL solutions. When both the PIL and IL contain large PFSI anions (a ≈ 0.57 nm), the specific viscosity ηsp first decreases with increasing IL concentration cIL in the low cIL regime, reaches a minimum and then increases with increasing cIL in the high cIL regime. By comparing the measured ηsp with the modified charge screening model proposed in our previous study [Matsumoto et al., Macromolecules, 2021, 54, 5648-5661], we attribute the observed non-monotonic trend of ηsp against cIL to the charge underscreening phenomenon, i.e., an increase of the screening length at high cIL leads to the upturn of ηsp. On the other hand, when the PIL and IL contain small BF4 anions (a ≈ 0.34 nm), the ηsp decreases asymptotically with increasing cIL, because the charge on the PIL chain is likely screened fully in the entire cIL regime. Our results demonstrate that the ion diameter of ILs plays an important role in governing the charge screening mechanism of PILs in IL solutions, and thus influencing the viscoelastic properties of PIL solutions.

Ionic liquids design for efficient separation of anthracene and carbazole

• COSMO-RS is applied to screen ionic liquids for separation of anthracene and carbazole. • The anthracene with high purity can be obtained by ionic liquids. • The anthracene and carbazole do not form solid solutions in Ionic liquids. • The separation mechanism of anthracene and carbazole in Ionic liquids is discussed. Anthracene (ANT) and carbazole (CAR) are highly value-added compounds in chemical industry. They are always mixed in preliminary processing products of high temperature coal tar and need to be separated and purified. In this study, ionic liquids (ILs) were used to separate ANT and CAR. [C 3 PY], [PM 2 IM] and [PMPIP] cations along with 7 classes of anions were screened by the conductor-like screening model for real solvents (COSMO-RS). [PMPIP][TFAc] (IL a ) and [PMPIP][Ac] (IL b ) were selected and synthesized. The structures of ILs were studied by σ-profile at the micro-level to analysis the hydrogen bonds formed between anion of ILs and H-N of CAR. The ternary phase diagrams of ANT-CAR-ILs were plotted to analysis the separation efficiency. Two ILs were used as extractant to separate ANT and CAR. The separation results showed that the synthesized ILs were the highly efficient solvents. The purity of refined ANT separated by IL b was improved to 97.87 wt%, with a yield of 80.04 wt%. The separation mechanism of ANT and CAR was further discussed.

Evaluation of ionanofluid for chemical-enhanced oil recovery for matured crude oil reservoirs

The purpose of the present work is to evaluate applicability of ionanofluids for enhanced oil recovery (EOR) applications. Two different ionanofluids have been prepared for this study by adding silica nanoparticles into two different ionic liquids (tripropyl ammonium sulphate and triethyl ammonium sulphate) solutions. The effects of nanoparticle and ionic liquid on the interfacial tension of crude oil-nanofluid and their enhanced oil recovery performances have been evaluated. Ionanofluids are found to have the ability to reduce the interfacial tension to a significantly low value. The results of this study also indicate that ionanofluids has much higher enhanced oil recovery efficiencies in comparison to nanofluid and ionic liquid alone. Therefore, ionanofluids have the potential to be used as an excellent future EOR agent. [Received: February 11, 2021; Accepted: April 13, 2021]

Subsistence of assorted molecular interactions of substantial amino acids prevalent in aqueous solutions of ionic liquid (TBMS) probed by experimental and computational investigations

Solution behaviour prevailing in L-Arginine and L-Histidine in aqueous Tetrabutylammonium methanesulphonate (TBMS) has been studied to investigate the mode of interactions by means of density (ρ), viscosity (η), surface tension (σ), refractive index (nD) and electrolytic conductivity at three different temperatures. The nature of interactions occurring in the solutions have been elucidated on the basis of apparent molar volume (Фv0), limiting molar expansivities (ФE0), viscosity A- and B- coefficients, molar refraction (RM) and concentration measurements. Molar conductance (Ʌ), obtained, so, describe the nature of solute–solute and solute–solvent interactions in the solution mixtures. Using Gaussian 09 W quantum chemical package, optimum energies with the optimised geometries of molecular assembly for (TBMS + L-Arginine) and (TBMS + L-Histidine) systems and also critical micelle concentration (CMC) values were calculated and found supportive to the practical outcomes that show the solute–solvent interactions prevailing between the TBMS (IL) and amino acids; L-Arginine and L-Histidine are dominant over the solute–solute interactions. Furthermore, L-Arginine shows a higher extent of interaction that is also influenced by the concentrations and temperatures in comparison to L-Histidine in aqueous IL solutions. The theoretical observations of the study determining Δμ10≠, Δμ20≠, ΔH0≠, and TΔS0≠ also imply the presence of strong interactions in the systems. The various types of interactions between amino acids which are the protein backbone, in presence of ionic liquids would develop a many-dimensional challenge in the field of solution chemistry. Studies of such systems could be advanced further using the correlated outcomes of the investigation.

Exploring the Subsistence of Solvation Consequences of L-Asparagine and L-Glutamine Prevailing in Aqueous Ionic Liquid Solutions by Physicochemical and Computational Investigations

Exploring the Subsistence of Solvation Consequences of L-Asparagine and L-Glutamine Prevailing in Aqueous Ionic Liquid Solutions by Physicochemical and Computational Investigations

A volumetric and intra-diffusion study of solutions of AlCl3 in two ionic liquids - [C2TMEDA][Tf2N] and [C4mpyr][Tf2N

Intra-diffusion coefficients (DSi) have been measured for the ionic liquid constituent ions and aluminium-containing species in aluminium chloride (AlCl3) solutions in the ionic liquids 1-(2-dimethyl-aminoethyl)-dimethylethylammonium bis(trifluoromethylsulfonyl)amide ([C2TMEDA][Tf2N]) and N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([C4mpyr][Tf2N]), to investigate whether spectroscopically detected interactions between the ions and AlCl3 affect these properties. Such electrolyte solutions are of interest for the electrowinning of aluminium. The temperature, composition and molar volume dependences are investigated. Apparent (Vϕ,1) and partial molar (V1) volumes for AlCl3 have been calculated from solution densities. For [C2TMEDA][Tf2N] solutions, Vϕ,1 increases with increasing solute concentration; for [C4mpyr][Tf2N] solutions, it decreases. In pure [C2TMEDA][Tf2N], the cation diffuses more quickly than the anion, but this changes as the AlCl3 concentration increases. In the [C4mpyr][Tf2N] solutions, the intra-diffusion coefficient ratio remains equal to that for the pure ionic liquid and the aluminium species diffuses at approximately the same rate as the anion at each composition. The intra-diffusion coefficients can be fitted to the Ertl-Dullien free volume power law by superposing the iso-concentration curves with concentration dependent, but temperature independent, molar volume offsets. This suggests that they are primarily dependent on the molar volume and secondarily on a colligative thermodynamic factor due to dilution by AlCl3. AlCl3 complexation by [Tf2N]- and [C2TMEDA]+, confirmed by 27Al, 15N and 19F NMR spectroscopy, seems to play a minor role. Our results indicate that the application of free volume theories might be fruitful in the study of the transport properties of ionic liquid solutions and mixtures.

Effect of Water and Salt on the Colloidal Stability of Latex Particles in Ionic Liquid Solutions

The colloidal stability of sulfate (SL) and polyimidazolium-modified sulfate (SL-IP-2) latex particles was studied in an ionic liquid (IL) of ethylammonium nitrate (EAN) and its water mixtures. Aggregation rates were found to vary systematically as a function of the IL-to-water ratio. Repulsive electrostatic interactions between particles dominated at low IL concentrations, while they were significantly screened at intermediate IL concentrations, leading to destabilization of the dispersions. When the IL concentration was further increased, the aggregation of latex particles slowed down due to the increased viscosity and finally, a striking stabilization was observed in the IL-rich regime close to the pure IL solvent. The latter stabilization is due to the formation of IL layers at the interface between particles and IL, which induce repulsive oscillatory forces. The presence of the added salt in the system affected differently the structure of the interfaces around SL and SL-IP-2 particles. The sign of the charge and the composition of the particle surfaces were found to be the most important parameters affecting the colloidal stability. The nature of the counterions also plays an important role in the interfacial properties due to their influence on the structure of the IL surface layers. No evidence was observed for the presence of long-range electrostatic interactions between the particles in pure ILs. The results indicate that the presence of even low concentrations of water and salt in the system (as undesirable impurities) can strongly alter the interfacial structure and thus, the aggregation mechanism in particle IL dispersions.

Surface Interaction of Ionic Liquids: Stabilization of Polyethylene Terephthalate-Degrading Enzymes in Solution.

The effect of aqueous solutions of selected ionic liquids solutions on Ideonella sakaiensis PETase with bis(2-hydroxyethyl) terephthalate (BHET) substrate were studied by means of molecular dynamics simulations in order to identify the possible effect of ionic liquids on the structure and dynamics of enzymatic Polyethylene terephthalate (PET) hydrolysis. The use of specific ionic liquids can potentially enhance the enzymatic hydrolyses of PET where these ionic liquids are known to partially dissolve PET. The aqueous solution of cholinium phosphate were found to have the smallest effect of the structure of PETase, and its interaction with (BHET) as substrate was comparable to that with the pure water. Thus, the cholinium phosphate was identified as possible candidate as ionic liquid co-solvent to study the enzymatic hydrolyses of PET.

Efficient Extraction of the RuBisCO Enzyme from Spinach Leaves Using Aqueous Solutions of Biocompatible Ionic Liquids

Ribulose-1,5-biphosphate carboxylase/oxygenase (RuBisCO) is the most abundant protein on the planet, being present in plants, algae and various species of bacteria, with application in the pharmaceutical, chemical, cosmetic and food industries. However, current extraction methods of RuBisCO do not allow high yields of extraction. Therefore, the development of an efficient and selective RuBisCOs’ extraction method is required. In this work, aqueous solutions of biocompatible ionic liquids (ILs), i.e., ILs derived from choline and analogues of glycine-betaine, were applied in the RuBisCO’s extraction from spinach leaves. Three commercial imidazolium-based ILs were also investigated for comparison purposes. To optimize RuBisCO’s extraction conditions, response surface methodology was applied. Under optimum extraction conditions, extraction yields of 10.92 and 10.57 mg of RuBisCO/g of biomass were obtained with the ILs cholinium acetate ([Ch][Ac]) and cholinium chloride ([Ch]Cl), respectively. Circular dichroism (CD) spectroscopy results show that the secondary structure of RuBisCO is better preserved in the IL solutions when compared to the commonly used extraction solvent. The obtained results indicate that cholinium-based ILs are a promising and viable alternative for the extraction of RuBisCO from vegetable biomass.

Thermodynamic study of interaction effects in aqueous solutions of purine and pyrimidine nucleobases ionic liquids at 298.15 K

We report herewith experimental density and osmotic pressure measurements for aqueous 1-ethyl-3-methylimidazolium ([Emim]), and 1-n-butyl-3-metylimidazolium ([Bmim]) based nucleobases ionic liquids [NBILs] at 298.15 K to gain thermodynamic understanding of NBIL – water mixtures. Molar volumes Vm, standard entropies S0 and lattice potential energies UPOT are reported at 298.15 K using density data of pure state NBILs. Large values of S0 and small UPOT explains the existence of NBILs in liquid state at ambient conditions. Experimental density data of aqueous NBIL solutions were used to obtain apparent, partial and electrostricted volumes from which electrostricted hydration numbers were obtained. It was found that observed hydration numbers are solely due to anion hydration as cation shows negligibly small hydration. Negative magnitudes of excess molar volumes confirm the hydrophobic nature of NBILs. Using experimental osmotic coefficients, water activity (aW), mean molal activity coefficient γ± of NBILs, excess Gibbs free energy change ΔGE due to mixing etc. were obtained and found that these aqueous systems show negative deviation from limiting law. At low concentration hydrophobic hydration is dominant whereas hydrophobic ion-association occurs at higher concentration revealed from minimum in osmotic coefficients. Application of McMillan–Mayer theory of solutions yielded osmotic second virial coefficients which are found to be negative indicating attractive type of ion-ion – ion-pair interactions.

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).