Search

Densities for solutions of [Cnmim]Br(n= 4, 8, 10, 12) ionic liquids (ILs) in dimethylsulfoxide (DMSO) have been determined as a function of ionic liquidconcentration at the temperature T= (293.15, 298.15,303.15, 308.15, and 313.5) K and atmospheric pressure. The apparentmolar volumes, apparent molar volumes at infinite dilution, and limitingapparent molar expansivities of the ILs have been obtained from theexperimental density data. These data were used to understand theeffect of the alkyl chain length of the ILs and experimental temperatureon the IL–DMSO interactions occurring in the studied solutions.It was shown that the apparent molar volumes at infinite dilutionincreased with increasing alkyl chain length of the ILs and temperatureof the systems. Furthermore, the values of the limiting apparent molarexpansibilities were found to be positive and decreasewith increasing temperature. [ABSTRACT FROM AUTHOR]

Carboxylate-anion-based imidazolium ionic liquids (ILs)are powerfulsolvents for cellulose and lignin. However, little is known abouttheir fundamental physicochemical properties. In this work, 1-butyl-3-methylimidazoliumcarboxylate ILs 1-butyl-3-methylimidazolium formate ([C4mim][HCOO]), acetate ([C4mim][CH3COO]), propionate([C4mim][CH3CH2COO]), and butyrate([C4mim][CH3(CH2)2COO]),in which the alkyl chain length in the anions is being varied in contrastto the more usual studies where alkyl chain length in the cationsis varied, have been synthesized and their densities and surface tensionshave been determined experimentally at different temperatures. Byusing these data, the molar volume, isobaric expansivity, standardentropy, lattice energy, surface excess entropy, vaporization enthalpy,and Hildebrand solubility parameter have been estimated for theseILs. From the analysis of structure–property relationship,the effect of alkyl chain length in the anions on these physicochemicalproperties of the ILs has been assessed and the dissolution of celluloseand lignin in these ILs has been discussed. Such knowledge is expectedto be useful for understanding the nature of this class of solventfor the dissolution of biomacromolecules. [ABSTRACT FROM AUTHOR]

Material preparation in ionic liquids and environmental pollution control by ionic liquids are often closely dependent on the aggregation behavior of ionic liquids in solution. In the present work, conductivity, fluorescence probe, and dynamic light scattering techniques have been used to study the effect of organic solvents on the aggregation behavior of 1-dodecyl-3-methylimidazolium bromide in water. It was shown that the critical aggregation concentration (CAC), the ionization degree of the aggregates (α), and the standard Gibbs energy of aggregation (ΔGm°) of the ionic liquid increase, while its aggregation number (Nagg) and aggregates’ size decrease with increasing concentration of organic additives in water. These results have been discussed from the favorable interactions of alkyl chain of the ionic liquid with the mixed solvents. It is suggested that the solvophobic parameter, characterized quantitatively by Gibbs energy of transfer of hydrocarbon from gas into a given solvent, can be used to account for the effect of organic additives on the formation and growth of the ionic liquid aggregates in water. Aggregation behavior of ionic liquids in aqueous organic solutions can be modulated simply by the solvophobic parameters of hydrocarbon in the mixed solvents. [ABSTRACT FROM AUTHOR]

Thermodynamicdissociation constants of the Brønsted acidicionic liquids (ILs) are important for their catalytic and separationapplications. In this work, a series of imidazolium bromides withone carboxylic acid substitute group in their alkyl chain ([{(CH2)nCOOH}mim]Br, n= 1,3,5,7) have been synthesized, and their dissociation constants(pKa) at different ionic strengths havebeen determined in aqueous and aqueous organic solvents at 0.1 molefraction (x) of ethanol, glycol, iso-propanol, anddimethyl sulfoxide by potentiometric titrations at 298.2 K. The standardthermodynamic dissociation constants (pKaT) of the ILs in these solvents were calculated from theextended Debye–Hückel equation. It was found that thepKavalues increased with the increaseof ionic strength of the media and of the addition of organic solventin water. The pKaTvalues alsoincreased with the increase of the alkyl chain length of cations ofthe ILs. In addition, the effect of solvent nature on pKaTvalues is interpreted from solvation ofthe dissociation components and their Gibbs energy of transfer fromwater to aqueous organic solutions. [ABSTRACT FROM AUTHOR]

Recently,it has been reported that addition of a cosolvent significantlyinfluences solubility of cellulose in ionic liquids (ILs), but littleis known about the influence mechanism of the cosolvent on the molecularlevel. In this work, four kinds of typical molecular solvents (dimethylsulfoxide (DMSO), N,N-dimethylformamide(DMF), CH3OH, and H2O) were used to investigatethe effect of cosolvents on cellulose dissolution in [C4mim][CH3COO] by molecular dynamics simulations and quantumchemistry calculations. It was found that dissolution of cellulosein IL/cosolvent systems is mainly determined by the hydrogen bondinteractions between [CH3COO]−anionsand the hydroxyl protons of cellulose. The effect of cosolvents onthe solubility of cellulose is indirectly achieved by influencingsuch hydrogen bond interactions. The strong preferential solvationof [CH3COO]−by the protic solvents (CH3OH and H2O) can compete with the cellulose–[CH3COO]−interaction in the dissolution process,resulting in decreased cellulose solubility. On the other hand, theaprotic solvents (DMSO and DMF) can partially break down the ionicassociation of [C4mim][CH3COO] by solvationof the cation and anion, but no preferential solvation was observed.The dissociated [CH3COO]−would readilyinteract with cellulose to improve the dissolution of cellulose. Furthermore,the effect of the aprotic solvent-to-IL molar ratio on the dissolutionof cellulose in [C4mim][CH3COO]/DMSO systemswas investigated, and a possible mechanism is proposed. These simulationresults provide insight into how a cosolvent affects the dissolutionof cellulose in ILs and may motivate further experimental studiesin related fields. [ABSTRACT FROM AUTHOR]

The inherent structure tunability, good affinity with CO2, and nonvolatility of ionic liquids (ILs) drive their exploration and exploitation in CO2 separation field, and has attracted remarkable interest from both industries and academia. The aim of this Review is to give a detailed overview on the recent advances on IL-based materials, including pure ILs, IL-based solvents, and IL-based membranes for CO2 capture and separation from the viewpoint of molecule to engineering. The effects of anions, cations and functional groups on CO2 solubility and selectivity of ILs, as well as the studies on degradability of ILs are reviewed, and the recent developments on functionalized ILs, IL-based solvents, and IL-based membranes are also discussed. CO2 separation mechanism with IL-based solvents and IL-based membranes are explained by combining molecular simulation and experimental characterization. Taking into consideration of the applications and industrialization, the recent achievements and developments on the transport properties of IL fluids and the process design of IL-based processes are highlighted. Finally, the future research challenges and perspectives of the commercialization of CO2 capture and separation with IL-based materials are posed. [ABSTRACT FROM AUTHOR]

Inthis work, four 1-butyl-3-methylimidazolium carboxylate ionicliquids (ILs) with different substituent groups in anions, including1-butyl-3-methylimidazolium glycollate [C4mim][HOCH2COO], 1-butyl-3-methylimidazolium lactate [C4mim][CH3CHOHCOO], 1-butyl-3-methylimidazolium benzoate [C4mim][C6H5COO], and 1-butyl-3-methylimidazoliumglycinate [C4mim][H2NCH2COO], havebeen synthesized and characterized. Their densities (ρ) andsurface tensions (γ) have been determined experimentally inthe temperature range of (298.15 to 343.15) K. By using thermodynamicand empirical equations, molar volume (Vm), isobaric expansivity (αp), standardentropy (S°), lattice energy (UPOT), surface excess entropy (Ss), vaporization enthalpy (ΔlgHm0) and Hildebrand solubility parameter(δH) of these ILs have been derived from densityand surface tension data. The effects of substituent groups in carboxylateanions on densities and surface tensions of these ILs have been assessedfrom the analysis of the structure–property relationship. [ABSTRACT FROM AUTHOR]