Thermophysical Properties of Imidazolium-Based Ionic Liquids
10 Jun 2004-Journal of Chemical & Engineering Data (American Chemical Society)-Vol. 49, Iss: 4, pp 954-964
TL;DR: In this paper, the authors present density as a function of temperature, melting temperatures, glass transition temperatures, decomposition temperatures, and heat capacities for 13 ionic liquids, including 1-butyl-3-methylimidazolium trifluoromethanesulfonate.
Abstract: Ionic liquids (ILs) are salts that are liquid at low temperatures, usually including the region around room temperature. They are under intense investigation, especially as replacement solvents for reactions and separations, since they exhibit negligible vapor pressure and would not, therefore, contribute to air pollution. Clearly, basic thermophysical properties are vital for design and evaluation for these applications. We present density as a function of temperature, melting temperatures, glass-transition temperatures, decomposition temperatures, and heat capacities as a function of temperature for a series of 13 of the popular imidazolium-based ILs. The ionic liquids investigated here are 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium dicyanamide, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium tris(trifluoromethylsul...
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TL;DR: In this paper, a survey on the latest most representative developments and progress concerning ionic liquids, from their fundamental properties to their applications in catalytic processes, is presented, highlighting their emerging use for biomass treatment and transformation.
Abstract: This review gives a survey on the latest most representative developments and progress concerning ionic liquids, from their fundamental properties to their applications in catalytic processes. It also highlights their emerging use for biomass treatment and transformation.
1,471 citations
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TL;DR: Ionic liquids with the bis(trifluoromethylsulfonyl) imide anion had the largest affinity for CO(2), regardless of whether the cation was imidazolium, pyrrolidinium, or tetraalkylammonium.
Abstract: This work presents the results of solubility measurements for a series of gases in 1-n-butyl-3-methyl imidazolium tetrafluoroborate and 1-n-butyl-3-methyl imidazolium bis(trifluoromethylsulfonyl) imide. The gases considered include benzene, carbon dioxide, nitrous oxide, ethylene, ethane, oxygen, and carbon monoxide. Carbon dioxide and oxygen solubilities are also reported in methyl-tributylammonium bis(trifluoromethylsulfonyl) imide, butyl-methyl pyrrolidinium bis(trifluoromethylsulfonyl) imide, and tri-isobutyl-methyl phosphonium p-toluenesulfonate. We report the associated Henry's constants and enthalpies and entropies of absorption. In general, benzene, followed by carbon dioxide and nitrous oxide, have the highest solubilities and strongest interactions with the ionic liquids, followed by ethylene and ethane. Oxygen had very low solubilities and weak interactions. Carbon monoxide had a solubility below the detection limit of our apparatus. Ionic liquids with the bis(trifluoromethylsulfonyl) imide ani...
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TL;DR: A comprehensive review of superparamagnetic colloid research can be found in this article, with a focus on those systems that can be prepared as monodisperse samples and in relatively large quantities.
Abstract: The aim of this article is to provide a comprehensive review of current research activities that center on superparamagnetic colloids. We begin with an overview of synthetic strategies that have been developed for generating both nanoscale and mesoscale superparamagnetic colloids, with a focus on those systems that can be prepared as monodisperse samples and in relatively large quantities. We then discuss a variety of techniques that have been exploited for modifying surface properties, as well as for controlling the assembly and patterning of these magnetically active colloids. Towards the end, we highlight a range of innovative applications enabled by the unique combination of superparamagnetism and colloidal suspension. We conclude this review article with personal remarks and perspectives on the directions toward which future research in this area might be directed.
880 citations
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TL;DR: In this article, the authors provide a detailed overview of the achievements and difficulties that has been encountered in finding a suitable ionic liquid for CO2 capture from flue-gas streams.
Abstract: Economical and environmental aspects are the main motivation for research on energy efficient processes and the search for environment friendly materials for CO2 capture. Currently, CO2 capture is dominated by amine-based (e.g., monoethanolamine) technologies, which are very energy intensive and less attractive from an environmental point of view due to emissions of the used volatile solvent components. Ionic liquids have been proposed as a promising alternative to the conventional volatile solvents, because of their low volatility and other interesting properties. This remarkable interest has led to a rapid growth of literature on this specific subject. The aim of the present review paper is to provide a detailed overview of the achievements and difficulties that has been encountered in finding a suitable ionic liquid for CO2 capture from flue-gas streams. A major part of this review includes an overview of the experimental data of CO2 solubility, selectivity, and diffusivity in different ionic liquids. ...
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TL;DR: In this paper, the authors measured the viscosity and density of six ionic liquids (1-butyl-3-methylimidazolium hexafluorophosphate, 1-Butyl 3methylammonium bis(trifluoromethylsulfonyl)imide, butyltrimethylammmonium, ethyl sulfate and butyl trifluoric acid) with an accuracy of 10−3 g cm−3 and 1%, respectively.
762 citations
References
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TL;DR: There are indications that switching from a normal organic solvent to an ionic liquid can lead to novel and unusual chemical reactivity, which opens up a wide field for future investigations into this new class of solvents in catalytic applications.
Abstract: Ionic liquids are salts that are liquid at low temperature (<100 degrees C) which represent a new class of solvents with nonmolecular, ionic character. Even though the first representative has been known since 1914, ionic liquids have only been investigated as solvents for transition metal catalysis in the past ten years. Publications to date show that replacing an organic solvent by an ionic liquid can lead to remarkable improvements in well-known processes. Ionic liquids form biphasic systems with many organic product mixtures. This gives rise to the possibility of a multiphase reaction procedure with easy isolation and recovery of homogeneous catalysts. In addition, ionic liquids have practically no vapor pressure which facilitates product separation by distillation. There are also indications that switching from a normal organic solvent to an ionic liquid can lead to novel and unusual chemical reactivity. This opens up a wide field for future investigations into this new class of solvents in catalytic applications.
5,387 citations
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TL;DR: New, hydrophobic ionic liquids with low melting points (<−30 °C to ambient temperature) have been synthesized and investigated, based on 1,3-dialkyl imidazolium cations and hydrophilic anions and thus water-soluble.
Abstract: New, hydrophobic ionic liquids with low melting points (<−30 °C to ambient temperature) have been synthesized and investigated, based on 1,3-dialkyl imidazolium cations and hydrophobic anions. Other imidazolium molten salts with hydrophilic anions and thus water-soluble are also described. The molten salts were characterized by NMR and elemental analysis. Their density, melting point, viscosity, conductivity, refractive index, electrochemical window, thermal stability, and miscibility with water and organic solvents were determined. The influence of the alkyl substituents in 1, 2, 3, and 4(5)-positions on these properties was scrutinized. Viscosities as low as 35 cP (for 1-ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)amide (bis(triflyl)amide) and trifluoroacetate) and conductivities as high as 9.6 mS/cm were obtained. Photophysical probe studies were carried out to establish more precisely the solvent properties of 1-ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)amide). The hydrophobi...
4,089 citations
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TL;DR: A series of hydrophilic and hydrophobic 1-alkyl-3-methylimidazolium room temperature ionic liquids (RTILs) have been prepared and characterized to determine how water content, density, viscosity, surface tension, melting point, and thermal stability are affected by changes in alkyl chain length and anion.
3,469 citations
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TL;DR: In this paper, the authors used ATR and transmission IR spectroscopy to investigate the state of water in room temperature ionic liquids (RTILs) based on the 1-alkyl-3-methylimidazolium cation with the anions.
Abstract: ATR and transmission IR spectroscopy have been used to investigate the state of water in room temperature ionic liquids (RTILs) based on the 1-alkyl-3-methylimidazolium cation with the anions: [PF6]−, [SbF6]−, [BF4]−, [ClO4]−, [CF3SO3]−, [(CF3SO2)2N]−, [NO3]− and [CF3CO2]−. It has been shown that in these RTILs water molecules absorbed from the air are present mostly in the “free”
(not self-associated) state, bound via H-bonding with [PF6]−, [BF4]−, [SbF6]−, [ClO4]−, [CF3SO3]−, [(CF3SO2)2N]− with the concentrations of dissolved water in the range 0.2–1.0 mol dm−3. It has been concluded that most of the water molecules at these concentrations exist in symmetric 1 : 2 type H-bonded complexes: anion...HOH...anion. Additional evidence that the preferred sites of interaction with water molecules are the anions has been obtained from the experiments with RTILs of the 1-butyl-2,3-dimethylimidazolium and 1-butyl-2,3,4,5-tetramethylimidazolium cations. Water molecules can also form associated liquid-like formations in RTILs with anions of stronger basicity such as [NO3]− and [CF3CO2]−. When these RTILs are exposed to air the water concentrations exceed 1.0 mol dm−3. The strength of H-bonding between water molecules and anions increases in the order [PF6]− < [SbF6]− < [BF4]− < [(CF3SO2)2N]− < [ClO4]− < [CF3SO3]− < [NO3]− < [CF3CO2]−. The energies of this H-bonding were estimated from spectral shifts, with the resulting enthalpies being in the range 8–13 kJ mol−1. ATR-IR spectroscopy has also been used to study H-bonding between methanol and RTILs.
1,366 citations
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1,356 citations