Are Ionic Liquids Chemically Stable?

Wang, Binshen; Qin, Li; Mu, Tiancheng; Xue, Zhimin; Gao, Guohua

doi:10.1021/acs.chemrev.6b00594

Cited by 504 publications

(292 citation statements)

References 173 publications

(233 reference statements)

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“…Based on the identification of the formation of phosphane tellurides by NMR spectroscopy, one pathway for the decomposition of the quaternary phosphonium ILs may be via an S N 2 attack of the anion of the ILs at higher temperatures . We propose that one of the alkyl substituents of the quaternary phosphonium cation is abstracted to form the alkyl dicyanamide along with the corresponding trialkylphosphane.…”

Section: Resultsmentioning

confidence: 99%

“…ILs are usually considered as stable and chemically inert under the chosen reaction conditions . However, if a decomposition of the IL occurs, a change in its chemical and physical properties, such as conductivity, viscosity, and dissolving capacity influences the mechanism of the reaction and may be detrimental to product formation . On the other hand, the deliberate decomposition of an IL can also be used during a reaction process as exemplified by Taubert and co‐workers for the synthesis of CuCl nanoplatelets by degeneration of a Cu‐containing IL .…”

Section: Introductionmentioning

confidence: 99%

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Understanding the Chemical Reactivity of Phosphonium‐Based Ionic Liquids with Tellurium

Zhang

Schwedtmann

Weigand

et al. 2018

Chemistry A European J

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The chemical reactivity of phosphonium based ionic liquids (ILs) towards tellurium at temperatures above 220 °C was systematically investigated by a series of dissolution experiments, tracking the solute tellurium species by nuclear magnetic resonance, and characterizing the reaction products by X‐ray diffraction and scanning electron microscopy. The initial step is the thermal elimination of an alkyl group of the phosphonium cation of the ILs, most probably via an SN2 mechanism. The addition of tellurium follows to form trialkylphosphane tellurides as evidenced by 31P and 125Te NMR spectroscopic experiments. The trialkylphosphane tellurides can serve as a tellurium reservoir for the formation of metal tellurides, like Bi2Te3 and Ag2Te. It was observed that trihexyltetradecylphosphonium chloride ([P6 6 6 14]Cl) shows a very weak reactivity that is reflected by a low solubility of tellurium, while trihexyltetradecylphosphonium dicyanamide/decanoate ([P6 6 6 14][N(CN)2]/[P6 6 6 14][decanoate]) and tetrabutylphosphonium decanoate ([P4 4 4 4][decanoate]) dissolve tellurium to a much higher extent. We attribute these observations to the different Lewis basicity of the anions of the ILs as main influencing factor.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Understanding the Chemical Reactivity of Phosphonium‐Based Ionic Liquids with Tellurium

Zhang

Schwedtmann

Weigand

et al. 2018

Chemistry A European J

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“…The thermal stability of ILs mainly depends on the IL structure (i.e. cation/anion type) and cation modification (chain length, substituent number, C2 methylation and functionalization) [38]. The decomposition temperature could change from 200 to 400°C by varying the anion type, which indicates that anions play the most important role in determining thermal stability; [HSO 4 ]-based ILs (with [BMIM] or [BPy] cation) are moderately stable (300°C ≤ T onset < 350°C) [39].…”

Section: Resultsmentioning

confidence: 99%

Optimization and kinetic study of methyl laurate synthesis using ionic liquid [Hnmp]HSO ₄ as a catalyst

et al. 2018

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Methyl laurate was synthesized from lauric acid (LA) and methanol via an esterification reaction using ionic liquids (ILs) as catalysts. The efficiencies of three different catalysts, 1-methylimidazole hydrogen sulfate ([Hmim]HSO4), 1-methyl-2-pyrrolidonium hydrogen sulfate ([Hnmp]HSO4) and H2SO4, were compared. The effect of the methanol/LA molar ratio, reaction temperature, reaction time and catalyst dosage on the esterification rate of LA was investigated by single-factor experiments. Based on the single-factor experiments, the esterification of LA and methanol was optimized using response surface methodology. The results showed that the most effective catalyst was the IL [Hnmp]HSO4. The optimal conditions were as follows: [Hnmp]HSO4 dosage of 5.23%, methanol/LA molar ratio of 7.68 : 1, reaction time of 2.27 h and reaction temperature of 70°C. Under these conditions, the LA conversion of the esterification reached 98.58%. A kinetic study indicated that the esterification was a second-order reaction with an activation energy and a frequency factor of 68.45 kJ mol−1 and 1.9189 × 109 min−1, respectively. The catalytic activity of [Hnmp]HSO4 remained high after five cycles.

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“…In recent years, a novel concept of hypergolic ionic liquids (ILs) has emerged to address the challenges offered by hydrazine derivatives. This is because of their enhanced physicochemical properties, including extremely low volatility, low toxicity, good thermal stability, high loading density, wide liquid range, short ignition delay, and good thrust control . Moreover, the properties of hypergolic ILs can be readily varied and tuned through the modification of the cationic and/or anionic components.…”

Section: Introductionmentioning

confidence: 76%

Synthesis and Properties of Azide‐Functionalized Ionic Liquids as Attractive Hypergolic Fuels

Wang

Pan

Wang

et al. 2019

Chemistry An Asian Journal

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Hypergolic ionic liquids (ILs) have shown a great promise as viable replacements for toxic and volatile hydrazine derivatives used as propellant fuels, and hence, have attracted increasing interest over the last decade. To take advantage of the reactivity and high energy density of the azido group, a family of low‐cost and easily prepared azide‐functionalized cation‐based ILs, including fuel‐rich anions, such as nitrate, dicyanamide, and nitrocyanamide anions, were synthesized and characterized. All the dicyanamide‐ and nitrocyanamide‐based ILs exhibited spontaneous combustion upon contact with 100 % HNO3. The densities of these hypergolic ILs varied in the range 1.11–1.29 g cm−3, and the density‐specific impulse, predicted based on Gaussian 09 calculations, was between 289.9 and 344.9 s g cm−3. The values of these two key physical properties are much higher than those of unsymmetrical dimethylhydrazine (UDMH). Among the studied compounds, compound IL‐3b, that is, 1‐(2‐azidoethyl)‐1‐methylpyrrolidin‐1‐ium dicyanamide, shows excellent integrated properties including the lowest viscosity (30.9 M Pa s), wide liquid operating range (−70 to 205 °C), shortest ignition‐delay time (7 ms) with 100 % HNO3, and superior density specific impulse (302.5 s g cm−3), suggesting promising applications with potential as bipropellant formulations.

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Are Ionic Liquids Chemically Stable?

Cited by 504 publications

References 173 publications

Understanding the Chemical Reactivity of Phosphonium‐Based Ionic Liquids with Tellurium

Understanding the Chemical Reactivity of Phosphonium‐Based Ionic Liquids with Tellurium

Optimization and kinetic study of methyl laurate synthesis using ionic liquid [Hnmp]HSO ₄ as a catalyst

Synthesis and Properties of Azide‐Functionalized Ionic Liquids as Attractive Hypergolic Fuels

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Are Ionic Liquids Chemically Stable?

Cited by 504 publications

References 173 publications

Understanding the Chemical Reactivity of Phosphonium‐Based Ionic Liquids with Tellurium

Understanding the Chemical Reactivity of Phosphonium‐Based Ionic Liquids with Tellurium

Optimization and kinetic study of methyl laurate synthesis using ionic liquid [Hnmp]HSO 4 as a catalyst

Synthesis and Properties of Azide‐Functionalized Ionic Liquids as Attractive Hypergolic Fuels

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Optimization and kinetic study of methyl laurate synthesis using ionic liquid [Hnmp]HSO ₄ as a catalyst