Ammonium-based Ionic Liquids Research Articles

Solubility and Thermodynamic Properties of Ammonium-Based Gemini Ionic Liquids in Pure Solvents

Asymmetrical ammonium-based gemini ionic liquids, 1-trimethylammonium-3-(1-methylpiperidinium)propane dibis[(trifluoromethyl)sulfonyl]imide ([N111C3MPip][NTf2]2) and 1-trimethylammonium-3-(4-methylmorpholinium)propane dibis[(trifluoromethyl)sulfonyl]imide ([N111C3MMor][NTf2]2), were synthesized and structurally characterized by 1H NMR, 13C NMR, and MS. The melting temperatures and associated enthalpies and entropies of fusion of these gemini ionic liquids have been determined through differential scanning calorimetry (DSC). Thermal stabilities of [N111C3MPip][NTf2]2 and [N111C3MMor][NTf2]2 have been investigated by thermogravimetric analysis technology under pure nitrogen atmosphere. The solubility data of [N111C3MPip][NTf2]2 and [N111C3MMor][NTf2]2 in water, ethanol, benzyl alcohol, 2-phenylethanol and n-heptane were determined by a synthetic method using a laser monitoring observation technique in the temperature range 298.15–333.15 K under atmospheric pressure. The solubility in all pure solvents increased with the increasing temperature and the greatest solubilities of both gemini ionic liquids were observed in benzyl alcohol. The modified Apelblat, Buchowski–Ksiazaczak λh and NRTL models were employed to correlate the experimental solubility data. The calculated results show good agreement with the experimental data and modified Apelblat and λh equations are more accurate than the NRTL model. The standard state enthalpy, entropy, and Gibbs energy of dissolution of the GILs in the studied solvents were evaluated through the van′t Hoff equation using the experimental solubility data. The excess enthalpies of the solutions were also determined by the λh model. The dissolution behavior can serve for the synthesis and purification process of GILs.

Effect of physicochemical properties of ammonium-based ionic liquids on CO2 capturing: An insight into structure-activity relationship

The physicochemical properties including density, viscosity and refractive index of five ionic liquids (ILs) consisting of 2-acrylamido-2-methylpropanesulfonate [AMPS] as anion source with ammonium-based cations (tetrabutylammonium [TBA], tetrapropylammonium [TPA] and tetraethylammonium [TEA], tetramethylammonium [TMA] and (vinylbenzyl)trimethylammonium [vbn]) were measured and influence of these properties upon CO2 sorption was investigated. The viscosity and density measurements were taken at atmospheric pressure within the temperature range of (293.15–363.15) K, whereas refractive indexes were determined within (288.15–333.15) K. An increase in the side-carbon chain length of ammonium-based cations resulted in decreased density with a corresponding increase in viscosity and refractive index. Among the studied ILs, [TBA][AMPS] gave the highest viscosity and least density over the whole range of temperature and a higher CO2 sorption of 0.51 mol fraction at 298.15 K and 1 MPa was observed showing dependency of CO2 solubility on the thermophysical properties of studied ILs. Moreover, among investigated ILs, molar volume of [TBA][AMPS] was found to be largest (433.3729 cm3mol-1), which resulted in the higher amount of CO2 sorption in comparison to other investigated ILs. Also, Henry's constant of 1.51 MPa was found for [TBA][AMPS] which was 10.9, 33.4, 44.3 and 24.8% less than [TPA][AMPS], [TEA][AMPS], [TMA][AMPS] and [vbn][AMPS], respectively. The current work offers an in depth study to understand structure-activity relation between physicochemical properties and CO2 solubility of investigated ILs and explores the ways for enhanced CO2 sorption.

NH3absorption in Brønsted acidic imidazolium- and ammonium-based ionic liquids

The Brønsted ionic liquids, consisting of sulfo and carboxy groups, absorbed larger amounts of NH3than the nonfunctionalized ionic liquids. The spectroscopic analyses indicated that the Brønsted ionic liquids absorbed NH3physically and chemically.

Self-Consistent Scheme Combining MD and Order-N DFT Methods: An Improved Set of Nonpolarizable Force Fields for Ionic Liquids

The nonpolarizable force field of ionic liquids is tuned by using the self-consistent scheme of molecular dynamics (MD) simulation and first-principles calculation based on the order-N density functional theory (DFT). The atomic charges are determined by using the whole MD cell for DFT calculation and accounts effectively for the many-body effects of charge transfer and intramolecular polarization. The charges represent effective interactions in the condensed phase within the framework of the nonpolarizable force field and can be an alternative for an explicitly many-body model incorporating, for example, polarizability. Here we demonstrate the performance of nonpolarizable force field determined with the MD-DFT self-consistent scheme in imidazolium-, pyrrolidinium-, and ammonium-based ionic liquids. The variation ranges of molecular charges are much larger with the compositions of the ionic liquid than with the thermodynamic conditions, and the charge-ordering structures become systematically weaker with the effective charges. For energetic properties, while the calculated heat of vaporization depends on the atomic and molecular charges, the corresponding heat capacity is not strongly affected by the DFT-based variation. For transport properties, the self-diffusion coefficient, electrical conductivity, and viscosity vary much more in the self-consistent scheme. The effective DFT charge is observed to enhance the fluidity of ionic liquids and improve the accuracy of electrical conductivity and viscosity. This is due to the weakened interactions among the ions, and the too slow motions observed with a full-charge model are well corrected through the iteration of MD and DFT. We therefore conclude that the set of nonpolarizable force fields obtained with the MD-DFT self-consistent scheme leads to better description of transport properties of ionic liquids.

A biophysical strategy to examine the impact of newly synthesized polymerizable ammonium-based ionic liquids on the structural stability and proteolytic activity of stem bromelain

The present manuscript reports the synthesis and characterization of polymerizable ammonium-based ionic liquids (ILs) and explores their influence on structural stability of stem bromelain (BMN) by using various biophysical techniques. Thermal fluorescence results showed that N-ethyl-2-(methylacryloyloxy)-N,N-dimethylethan-1-ammonium bromide (IL2C) (at lower concentration (0.1 mg/mL)) is found to be increasing the thermal stability of BMN which can be evident from the transition temperature (Tm) for BMN in IL2C (68.51 °C) is higher than BMN in buffer (66.24 °C). Whereas, N-(2-(methacryloyloxy)ethyl)-N,N-dimethylpropan-1-ammonium bromide (IL3C) and N-(2-(methacryloyloxy)ethyl)-N,N-dimethylpentan-1-ammonium bromide (IL5C) are maintaining the Tm values very near to Tm of pure BMN. Though, N-(2-(methacryloyloxy)ethyl)-N,N-dimethylhexan-1-ammonium bromide (IL6C) is found to be destabilizing IL as it significantly decreased the Tm value of BMN at all concentrations. Additionally, consequence of ILs on the proteolytic activity of BMN has also performed for IL2C up to 5 mg/mL while IL3C and IL5C at 0.1 mg/mL and 0.5 mg/mL are enhancing the proteolytic activity of BMN. Later, molecular docking studies are also performed with AutoDock vina and results showed that all ILs have different binding sites on BMN however IL6C is observed to be binding to the catalytic site of the BMN, it turns out to be the most destabilizing IL.

Thermophysical Properties and CO2 Absorption of Ammonium-Based Protic Ionic Liquids Containing Acetate and Butyrate Anions

Ionic liquids, which are classified as new solvents, have been identified to be potential solvents in the application of CO2 capture. In this work, six ammonium-based protic ionic liquids, containing ethanolammonium [EtOHA], tributylammonium [TBA], bis(2-ethylhexyl)ammonium [BEHA] cations, and acetate [AC] and butyrate [BA] anions, were synthesized and characterized. The thermophysical properties of the ammonium-based protic ionic liquids were measured. Density, ρ, and dynamic viscosity, η, were determined at temperatures between 293.15 K and 363.15 K. The density and viscosity values were correlated using empirical correlations and the thermal coefficient expansion, αp, and molecular volume, Vm, were estimated using density values. The thermal stability of the ammonium-based protic ionic liquids was investigated using thermogravimetric analyzer (TGA) at a heating rate of 10 °C·min‒1. The CO2 absorption of the ammonium-based ionic liquids were measured up to 20 bar at 298.15 K. From the experimental results, [BEHA][BA] had the highest affinity towards CO2 with the mol fraction of CO2 absorbed approaching 0.5 at 20 bar. Generally, ionic liquids with butyrate anions have better CO2 absorption than that of acetate anions while [BEHA] ionic liquids have higher affinity towards CO2 followed by [TBA] and [EtOHA] ionic liquids.

Enhanced extraction of astaxanthin using aqueous biphasic systems composed of ionic liquids and potassium phosphate

Shrimp waste containing a substantial amount of valuable nutrients presents a challenge for food industry. In this work, extraction of astaxanthin from shrimp waste via aqueous biphasic systems (ABS) composed of ionic liquids (ILs) and potassiumphosphate (K3PO4) was investigated. The influence of phosphonium- and ammonium-based ILs and temperature on the phase behavior and astaxanthin extraction was evaluated. The hydrogen-bond basicity of each IL studied shows a negative linear correlation with tie-line lengths of ABS and a positive linear correlation with extraction efficiency (EEAst). In general, lower temperature are favourable for astaxanthin extraction. Tributyloctylphosphonium bromide ([P4448]Br) resulted in the strongest ABS formation ability and bonding interactions between the anion and astaxanthin. Compared with organic solvents, [P4448]Br + K3PO4 ABS achieved higher EEAst of 93.08% at 308 K. The chemical properties provide the possibility of prescreening appropriate ILs for ABS formation and predicting the partition of a target molecule.

Positive electrode material in lead-acid car battery modified by protic ammonium ionic liquid

Abstract The aim of the presented study was to develop a feasible and technologically viable modification of a 12 V lead-acid battery, which improves its energy density, capacity and lifetime. The proposed solution promotes the addition of a protic ammonium ionic liquid to the active mass of the positive electrode in the lead-acid battery. The experiments included the synthesis and characterisation of several protic ammonium-based ionic liquids, which differed in terms of the length of the side chain in the cation. A three-stage procedure of the battery test was proposed. First, a laboratory model with a Pb-Ca-Sn alloy as a working electrode and ionic liquids as additives to the electrolytes enabled the selection of the best modifier. Addition of the best-studied ionic liquid, N,N-dimethylhexadecylammonium sulfate, suppressed the corrosion of current collector material by approx. 70% and increased the overpotential of hydrogen evolution reaction. Afterwards, tests on 2 V model lead-acid cells were carried out to compare the various concentrations of the ionic liquid in the active mass. Finally, tests on 12 V lead-acid batteries with 0.5% of protic ionic liquid were performed to evaluate the final influence on the full, industrial product.

Separation and recovery of rare earth elements using novel ammonium-based task-specific ionic liquids with bidentate and tridentate O-donor functional groups

In the present work, two novel ammonium-based functional ionic liquids (FILs) with oxygen donating groups: trioctyl(2-ethoxy-2-oxoethyl)ammonium dihexyl diglycolamate, [OcGBOEt][DHDGA], and tricaprylmethylammonium dihexyl diglycolamate, [A336][DHDGA] were synthesized and tested for the recovery and separation of rare earth elements from aqueous solutions. The synthesized FILs were characterized using nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), high-resolution mass spectrometry (HRMS), thermal gravimetric analysis (TGA), disc scanning calorimetry (DSC) in addition to density and viscosity analysis. The extraction behavior of europium ions (Eu3+) in HNO3 solution was investigated in detail by changing key process parameters, including solution acidity, concentration of Eu3+ ions, extraction temperature, extraction time, and the type of organic diluent. Kinetic studies indicated that the extraction process was relatively fast with 97% of Eu3+ions recovered after 5 min using [OcGBOEt][DHDGA], whereas it took 15 min for [A336][DHDGA] system to reach 80% recovery. Extraction thermodynamics was evaluated by analyzing the effect of temperature on the extractability of Eu3+ ions in nitrate solution. Results indicated that the extraction reactions were favorable for both FILs. Back extraction studies indicated that ~99% of Eu3+ can be stripped off [OcGBOEt][DHDGA] and [A336][DHDGA] using 0.1 and 0.5 molL−1 HNO3, respectively.Separation efficiencies of rare earth ions, including La3+, Pr3+, Nd3+, Sm3+, Eu3+, Tb3+, Dy3+, Y3+, Er3+, and Lu3+ were also investigated to examine the selectivity of the synthesized FILs. Results showed that both FILs have significant affinity to heavy rare earth elements, however, the separation efficiency of [A336][DHDGA] was superior to that of [OcGBOEt][DHDGA].

Ionic liquid electrolytes in electric double layer capacitors

Electric double layer capacitors (EDLCs), which store free charges on the electrode surface via non-Faradaic process, balanced by the electric double layer on the electrolyte side, exhibit excellent cycle stability and high power density. Though EDLCs are considered as promising energy storage devices, the charges stored on the electrode surface in EDLCs are much lower than those in batteries. Ionic liquids (ILs), as a new type of electrolytes in EDLCs, are capable to deliver high energy density, due to their excellent physicochemical properties and wide electrochemical window. In this review, we focus on the widely studied IL electrolytes for EDLCs, including pure ILs, IL/IL binary electrolytes, IL/organic solvent mixtures, as well as functionalized ILs, with attention on the relationship between the structures of different IL-based electrolytes and the energy storage properties in EDLCs. For imidazolium- and ammonium-based IL electrolytes which are most widely studied in EDLCs, the former generally have higher gravimetric specific capacitance, while the latter exhibit wider electrochemical window. The modifications of functional group substituted can be an effective strategy to enhance the gravimetric specific capacitance of the latter and thus improve the energy density of EDLCs.

Correction to “New Series of Green Cyclic Ammonium-Based Room Temperature Ionic Liquids with Alkylphosphite-Containing Anion: Synthesis and Physicochemical Characterization”

Correction to “New Series of Green Cyclic Ammonium-Based Room Temperature Ionic Liquids with Alkylphosphite-Containing Anion: Synthesis and Physicochemical Characterization”

Role of Cation Structure in CO2 Separation by Ionic Liquid/Sulfonated Polyimide Composite Membrane.

The development of suitable separation technologies for the separation of carbon dioxide is a pressing technological requirement. The application of ion gel membranes for this purpose continues to stimulate a great deal of research, and in this study we focus on the chemical structure of the ionic liquid component in the ion gel, and its interactions with the sulfonated polyimide polymer. Whilst such membranes are known to give promising carbon dioxide separation properties together with mechanical strength and thin-film-processability, we further elaborate on how changing the cation of the ionic liquid from a typical imidazolium cation to a protic variant effects the physicochemical, thermal, and structural properties of the membranes, and how these changes further influence the carbon dioxide separation properties. We compare and contrast our findings with our earlier study on protic and aprotic ammonium-based ionic liquids, and highlight that for CO2 absorption behavior in the imidazolium systems, the importance of directionality of interactions (ion pairs exhibit a large energy stabilization only for a specific geometrical arrangement of cation and anion, e.g., hydrogen bonding rather than Coulombic interaction) between cation and anion applies not only to the protic system, but also to the nominally aprotic cation. Finally, we demonstrate that the phase separation behavior in the ion gels is an important factor in determining the carbon dioxide separation behavior.

Ionic Liquid-in-Water Emulsion-templated Synthesis of Gold Nanoshells at the Liquid-Liquid Interface between Water and Primary Ammonium-based Ionic Liquids

Au nanoshells have been synthesized at the liquid-liquid interface between primary ammonium-based ionic liquids and water. Ionic liquid-in-water emulsions, which are spontaneously formed on the wat...

Synthesis of Quaternary Ammonium Room-Temperature Ionic Liquids and their Application in the Dissolution of Cellulose

In this work, several kinds of quaternary ammonium-based room-temperature ionic liquids (QA RTILs) are synthesized by alkylation and ion-exchange reactions for the rapid dissolution of cellulose. The applications of cellulose materials have been limited due to their poor solubility in conventional organic solvents, because of a high degree of structural regularity and a large number of hydrogen bonds. The prepared ionic liquids were identified by nuclear magnetic resonance, elemental analysis, and liquid chromatography-mass spectrometry. The results indicated that N,N,N-triethylhexan-1-aminium acetate (N6222OAc), tetrahexylammonium acetate (N6666OAc), and N,N,N,N′,N′,N′-hexaethyldecane-1,10-diaminium acetate (C10(N222OAc)2) exhibited good cellulose-dissolution without any pretreatment. The regenerated cellulose films with a low degree of crystallization of the cellulose II phase were also prepared easily in this process using N6222OAc due to its polar and small cation. These QA RTILs can be used as non-derivatizing solvents for cellulose and can also be easily recycled because of their thermostable and nonvolatile properties.

Aggregation Behavior of Pyrrolidinium Ionic Liquid Surfactants in −OH-Functionalized Ammonium-Based Protic Ionic Liquids

Aggregation of surfactants in ionic liquids (ILs) is poorly understood in spite of their great potential for applications in many fields. In this paper, the aggregation behavior of pyrrolidinium IL...

Chitin and chitosan production from shrimp shells using ammonium-based ionic liquids.

Ammonium-based ionic liquids (ILs): diisopropylethylammonium acetate ([DIPEA][Ac]), diisopropylethylammonium propanoate ([DIPEA][P]) and dimethylbutylammonium acetate ([DMBA][Ac]) are used for the extraction of chitin from shrimp shells. The extracted chitins were characterized by FT-IR, TGA, XRD, SEM and 1H NMR. The yield of chitin, with moderate molecular weights, can be as high as 13.4% (mass of extracted chitin/mass of shrimp shells) when the extraction was operated at 110 °C for 24 h. The extracted chitin can be further converted into chitosan and the product has 93% degree of deacetylation. The experimental results reveal that the ILs play a remarkable role in the extraction of chitin from shrimp shells with high selectivity. These ammonium-based ILs can be a promising green solvent to extract chitin from wasted shrimp shells and then converted into chitosan.

Separation of water/butan-1-ol with ionic liquids in ternary liquid-liquid phase equilibrium

In this work ionic liquids (ILs) as a novel popular solvents are proposed for removing butan-1-ol from the aqueous fermentation media. Ternary liquid-liquid phase equilibrium data are presented for mixtures of {ionic liquid (1) + butan-1-ol (2) + water (3)} at T = 328.15 K and ambient pressure. The ILs with long alkane chains such as hexadecyltrimethylammonium bis{(trifluomethyl)sulfonyl}imide, [N16,1,1,1][NTf2], 1,3-didecyl-2-methylimidazolium dicyanamide, [D2MIM][DCA] and tetrabutylphosphonium bis{(trifluomethyl)sulfonyl}imide, [P4,4,4,4][NTf2] have been tested. The results are discussed in terms of the selectivity and solute distribution ratio of separation of related systems. The complete miscibility in the binary liquid systems of butan-1-ol with three used ILs was observed. The ammonium-based IL in comparison with phosphonium-based IL shows lower selectivity and solute distribution ratio. The non-random two liquid NRTL model was used successfully to correlate the experimental tie-lines and to calculate the phase composition error in mole fraction in the ternary systems.

Surface Structure of Quaternary Ammonium-Based Ionic Liquids Studied Using Molecular Dynamics Simulation: Effect of Switching the Length of Alkyl Chains

The surface structure of four quaternary ammonium-based ionic liquids (QaILs) at the QaIL|vacuum interface has been analyzed using molecular dynamics simulation to investigate the effect of switchi...

The role of ionic-liquid extracted lignin micro/nanoparticles for functionalisation of an epoxy-based composite matrix

The present study aims to design high performance functionalized lignin-epoxy composites. In this work, the triethylammonium hydrogen sulphate ionic liquid (IL) was introduced onto the surface of lignin micro/nanoparticles while it was extracted from biomass, to prepare a highly functional and reinforcing IL-Lignin filler in an epoxy matrix. A bio-composite of IL-Lignin epoxy was prepared from IL-Lignin and a fast curing epoxy pre-polymer hardened with an anhydride-based curing agent using a simple one-step method. The thermal degradation mechanisms and the influence of the IL-Lignin on the thermal stability and cure kinetics of IL-Lignin epoxy networks have been investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Fourier Transformation Infrared spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) analysis confirm that the ammonium-based IL coupled with lignin is an effective promoter for crosslinking of the epoxy pre-polymer resulting in higher and faster degrees of conversion. Nuclear magnetic resonance spectroscopy reveals the characteristics of IL extracted lignin. Using atomic force microscopy (AFM) and dynamic light scattering (DLS), topographical features of the IL-Lignin surfaces and particle size of lignin at nanoscale were investigated and supporting evidence inferred underpinning the improved mechanical properties. The addition of 2 wt% IL-Lignin yielded an 80% increase in flexural strength (99.10 MPa), a 57% increase in flexural modulus (2.84 GPa), a 52% increase in tensile strength (40.90 MPa) and a 23% increase in toughness (86.08 kJ/m3), compared to the neat epoxy matrix. There was, however, a softening effect on the glass transition temperature due to the addition of IL-Lignin. This particular system of composite matrix is prone to controlled breakdown at the end of its lifecycle even after post cure due to biodegradable lignin linkages.

Asymmetric ammonium-based ionic liquids as electrolyte components for safer, high-energy, electrochemical storage devices

The synthesis of ionic liquids (ILs), based on the trimethyl-isobuty-ammonium cation, (N111i4)+, and, respectively, the bis(trifluoromethylsulfonyl)imide (TFSI), (fluorosulfonyl) (trifluoromethylsulfonyl)imide (FTFSI), and bis(fluorosulfonyl)imide (FSI) anions is herein reported. The NMR validation of the N111i4Br precursor as well as the ionic liquids is shown. The thermal properties were investigated via variable-temperature, coupled with mass spectroscopy, and isothermal thermo-gravimetrical analyses, and long-thermal tests. The TFSI-based IL exhibits a melting point of 29.93 °C, which is found to be shifted down to −0.12 and −14.32 °C for the FSI- and FTFSI-based samples, respectively. Additionally, the TFSI- and FTFSI-based samples are able to keep in super cooled state for more than one year. The investigated N111i4-based ionic liquids display an electrochemical stability window exceeding 5.5 V.