Thermal Stability Of Ionic Liquids Research Articles

Design, Synthesis, and Analysis of Thermophysical Properties for Imidazolium-Based Geminal Dicationic Ionic Liquids

To enhance the thermal stability of ionic liquids (ILs) and increase the latent heat, the effect of amount of hydrogen bonds for geminal dicationic ionic liquids (DILs) was investigated and compared to that of monocationic analogues. A series of geminal dicationic ionic liquids with alkyl chain or electronegativity functional groups in the imidazolium were synthesized. Thermal stability was determined by TGA; melting point, heat of fusion, and heat capacity were investigated by DSC for synthetic DILs. The effect of molecular structure on the heat of fusion was examined by changes alkyl side-chain, linkage chain, C2–H of imidazole ring, and functional groups. Hydrogen bonding in DILs was studied, in the case of C2(eim)2(Br)2, by single-crystal X-ray diffraction. The thermal analysis results indicate that functionalized geminal dicationic ionic liquids show excellent thermal stability. The decomposition temperatures of geminal dicationic ionic liquids can be up to 603.74 K, and the latent heat can reach 159...

Study on the absorbability, regeneration characteristics and thermal stability of ionic liquids for VOCs removal

A novel method of removal of volatile organic compounds (VOCs) using the ionic liquid [Bmim][NTf2] as an absorbent is developed as a contribution to dealing with recent severe smog incidents in China. The effects of concentration, temperature and flow rates on the ability of [Bmim][NTf2] to absorb VOCs were studied using toluene as a model volatile organic pollutant. The potential of the use of [Bmim][NTf2] as an absorbent for VOCs is shown by the solubility of toluene in the ionic liquid; the absorptivity of the ionic liquid for toluene; and the fact that absorbed toluene can be removed easily from [Bmim][NTf2], permitting recycle of the ionic liquid in multiple reuse phases. The solubility of toluene in [Bmim][NTf2] is 61.5% at 20°C and atmospheric pressure; the highest absorptivity of [Bmim][NTf2] for toluene is 98.3%, achieved at a toluene concentration of 300ppm and a flow rate of 50mLmin−1 at 20°C; and the absorptivity of the ionic liquid is>94% over a wide range of conditions. The ionic liquid can be recovered and recycled in the absorption process at least five times, reducing the reagent cost in the VOC removal process.

Thermokinetics of alkyl methylpyrrolidinium [NTf2] ionic liquids

The thermal degradation of two ionic liquids (ILs) was investigated using thermogravimetric analysis (TG) to establish a relationship between the thermokinetics and thermal stability. N-butyl, N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide [BMPyrro][NTf2] and N-octyl, N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide[OMPyrro][NTf2] were subjected to thermogravimetric analysis at varying heating rates of 5, 10 and 20 °C min−1 in the temperature range of 50–600 °C. The data obtained were analysed for thermokinetics using Ozawa, Kissinger and Starink methods using differential thermogravimetric (DTG) techniques, and Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS) and Starink methods using TG techniques. The results produced very high regression coefficients (R 2 ) values around 0.996, which exhibited that they were best fitted by the kinetics equations. The average calculated activation energy (E a) of [BMPyrro][NTf2] using FWO, KAS and Starink methods was 128.6, 123.6 and 124 kJ mol−1, respectively, and 113.7, 107.8 and 108.2 kJ mol−1, respectively, for [OMPyrro][NTf2] using same empirical methods. This emphasizes that the activation energy is strongly related to the length of the side alkyl chain of a given IL. In other words, the longer the side alkyl chain, the lower the activation energy. The E a trends with degree of conversion (α) suggest that a single mechanism without formation of intermediates or short-life intermediates was followed by the pyrolysis kinetics. This study introduced thermokinetics as a tool to study the thermal stability of ionic liquids.

Effect of Paramagnetic Metal Ions on 1H Diffusion in Trihexyltetradecylphosphonium Benzoate Ionic Liquid

Introduction The high thermal stability of ionic liquids has been exploited to be used in diverse applications (e.g., energy storage devices, extraction, lubrication etc.) [1-4]. The physicochemical properties (mobility, diffusion) of ionic liquids changes when used in a wide temperature range. Several methods are available to study the diffusion and mobility of ionic liquids, of all NMR is most accurate and reliable technique to study the translational (diffusion) and rotational motions in ionic liquids [5]. Pulsed field gradient spin echo and stimulated NMR has been utilized to study the diffusion process in ionic liquids [6-7]. Studies on the diffusion process in phosphonium based ionic liquids are scarce [8]. Moreover the effects of paramagnetic metal ion on the diffusion in ionic liquid are few. In this context we studied the effect of paramagnetic metal ion (neodymium) on the translational motion (diffusion) of Trihexyl-tetradecyl-phosphonium benzoate (P66614 TTPB) ionic liquid using pulsed field gradient NMR. Experimental Method TTPB (C39H73O2P) (KOEI chemicals Ltd., Japan, >98.0%) was used as received. Neodymium chloride (NdCl3, Wako Pure Chemical Industries, Japan) was dissolved in de ionized millipore water. The aqueous solutions were filtered using a 25 µm sieve to avoid precipitation. To start with, 0.5 ml aqueous NdCl3 is added to 1gm of TTPB and the mixture was shaken well for 60 min using a shaker followed by centrifugation for 60 min at 1000 rpm. The concentration of metal ion was measured by ICP-AES (Optima 3300XL, Perkin-Elmer, USA). 0.3 ml of neodymium containing TTPB is added to a 5 mm NMR glass tubes for 1H and NMR measurements. JEOL ECA 300 FT-NMR spectrometer operating at a frequency of 300.5 MHz for 1H nuclei was used to study the 1H diffusion. Results and Discussion Neodymium ion concentration in the TTPB ionic liquid was evaluated using ICP-AES and found to be in the range 0.02 mmol/L to 1.2 mmol/L. A small amount of water is found to be incorporated into the ionic liquid along with neodymium ions. Downfield shifts are observed in the 1H 1D NMR spectra with increasing neodymium concentration. 1H diffusion coefficients of the cation and anion were measured in the temperature range 24 - 80 °C. The temperature dependence of diffusion coefficient for different neodymium concentrations are shown in Fig. 1. As observed from Fig. 1 a, at low concentrations (0.02 ~ 0.1 mmol) the diffusion coefficient is in this order DH2O > Danion > Dcation. At higher concentrations (0.4 ~ 1.2 mmol) the diffusion coefficient of the cation and anion are almost the same as observed from Fig. 1 (DH2O ~ Danion ~ Dcation). Conclusion The presence of a paramagnetic ion (neodymium) in the ionic liquid shifts the proton chemical shift to lower field, due to its high magnetic dipole moment. From the diffusion results, 1H diffusion coefficient of the anion is higher than the cation at low concentration of neodymium. The anionic diffusion coefficient decreases with increasing neodymium concentration and converges with the cationic diffusion coefficient. This is possibly due to the formation of clusters around the neodymium ion at high concentrations. References E.Binetti, A.Panniello, L.Triggiani, R.Tommasi, A.Agostiano, M. L. Curri and M. Striccoli, J. Phys. Chem. B, 2012, 116, 3512.R. Atkin and G. G. Warr, J. Phys. Chem. C, 2007, 111, 5162.H. Tokuda, K. Hayamizu, K. Ishii, M. A. B. H. Susan and M. Watanabe, J. Phys. Chem. B, 2005, 109, 6103.F. U. Shah, S. Glavatskih, P. M. Dean, D. R. MacFarlane, M. Forsyth and O. N. Antzutkin, J. Mater. Chem., 2012, 22, 6928–6938.W. Price, NMR studies of translational motion, Cambridge University Press, 2009, p. 393.K. Hayamizu, S. Tsuzuki, S. Seki and Y. Umebayashi, J. Chem. Phys., 2011, 135, 084505.K. Hayamizu, S. Tsuzuki, S. Seki and Y. Umebayashi, J. Phys. Chem. B, 2012, 116, 11284–11291.Andrei Filippov, Faiz Ullah Shah, Mamoun Taher, Sergei Glavatskih and Oleg N. Antzutkin, Chem. Phys. Phys. Chem., 2013, 15, 9281. Figure 1

Effect of the cation structure on the thermal stability of ionic liquids, quaternary ammonium tetrachloroferrates(III)

New ionic liquids, tetrachloroferrates(III) of quaternary ammonium salts [(CH3)2NR1R2]FeCl4 [R1 = CH3; C4H9; (CH2)3CN. R2 = C10H21; C16H33; CH2CH2OH; CH2C6H5], were synthesized and their thermal stability was investigated in air in the range 25–600°С. The mechanism of thermal decomposition of the investigated ionic liquids is suggested in agreement with Hofmann’s rule as β-E2-elimination.

Thermal reaction of the ionic liquid 1,2-dimethyl-(3-aminoethyl) imidazolium tetrafluoroborate: a kinetic and theoretical study.

Since the thermal stabilities of ionic liquids (ILs) are of significance for their application, an amine-functionalized IL 1,2-dimethyl-(3-aminoethyl) imidazolium tetrafluoroborate [aEMMIM][BF4] was chosen to study thermal decomposition mechanisms via the methods of FT-IR, (1)H NMR, TGA, TGA-MS and density functional theory (DFT) calculations. Theoretical and experimental results indicated that amine-functionalization reduces the thermal stability of [aEMMIM][BF4] compared to its non-functionalized counterpart. Moreover, we found that [aEMMIM][BF4] follows a unimolecular nucleophilic substitution (SN1) decomposition (98.8%), whereas the bimolecular nucleophilic substitution (SN2) decomposition (1.2%) is unfavorable. The SN1 and SN2 reactions were fully optimized at B3LYP/6-311++G(d,p) level, and the energies of reactant (R), intermediates (IM), transition state (TS) and product (P) were obtained and analyzed by reaction mechanism. The energy of the intermediate is higher than that of the reactants by 18.92kJmol(-1), and the energy of the TS is higher than that of the IM by 155.23kJmol(-1). This result indicates that the IM are also more stable than the P2 product, thus the reaction is endothermic. The chemical nature of the covalent and hydrogen bonds was analyzed by vibrational modes analysis (VMA), nature bond orbital (NBO) and the theory of atoms in molecules (AIM). Graphical Abstract Proposed thermal decomposition of [aEMMIM][BF4] via unimolecular ( SN1) and bimolecular( SN2) nucleophilic substitution mechanisms. The electrostatic potential surface (ESP) of the transition state illustrates that hydrogen bonds are generated when [BF4](-) is close to [aEMMIM](+), and SN1 decomposition is much favorable than SN2 decomposition.

Synthesis of efficient SBA-15 immobilized ionic liquid catalyst and its performance for Friedel–Crafts reaction

Friedel–Crafts alkylation of benzene with 1-dodecene, which is an important reaction of synthetic detergent, was studied via ionic liquid [bmim][TFSI]/AlCl3 (1-butyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide/AlCl3) immobilized on SBA-15 catalysts. XRD, BET, TEM, TG, ammonia TPD investigations were used to search insight into catalyst characteristic. The immobilized catalysts preserved ordered structure and presented high specific surface areas. The utilization of active sites was significantly improved by immobilization. Based on ammonia TPD, immobilized catalysts exhibited higher Lewis acidity than aluminum chloride grafted SBA-15. TG indicated that thermal stability of ionic liquid has been improved by immobilization. The influences of various reaction conditions including reaction time, benzene/1-dodecene ratio were studied. Immobilized ionic liquids have better performance of no matter 1-dodecene conversion or 2-linear alkyl benzene (2-LAB) selectivity, than bulk ionic liquid catalysts or aluminum chloride grafted mesoporous materials. 2-LAB selectivity can be increased from about 35% with bulk ionic liquid to more than 60% with immobilized catalysts. Under optimal condition, 2-LAB selectivity reached as high as 80%. The immobilized catalysts could be reused. And at 3th cycle of catalysts, 1-dodecene conversion could still reach more than 50%. The role of deactivation was proposed based on TEM, BET and TG investigations. By-products as oligomer, produced by oligomerization of olefin, blocked or covered the pores, led to deactivation of catalysts.

The High Temperature Operation of Lithium Secondary Batteries with Using Ionic Liquids

Ionic liquids (ILs) composed of perfluoroanion such as BF4 − and bis(trifluoromethylsulfonyl)amide (([(CF3SO2)2N]−, Tf2N−) have attracted attention as less flammable and less volatile electrolyte for a lithium secondary battery for past decade. Especially, Tf2N- forms ILs not only 1-ethyl-3-methylimidazolium (C2mim+), but also various aliphatic quaternary ammonium (AQA+). The AQA-Tf2N exhibited large apparent electrochemical windows enough wide to use a solvent free electrolyte for a 4 V-class battery such as a LiCoO2 half-cell. Though the rate properties of the cell at room temperature were much lower than that for a conventional organic solvents, another promising ILs composed of bis(fluoromethylsulfonyl)amide (f2N−) are dramatically improved the rate property of the cells using ILs. However, it should be focused on not only the rate performance but also the actual thermal stability of the cells using ILs, which might not depend on only the thermal stability of ILs.[1] In this presentation, we would like to show the effect of cationic species of Tf2N--ILs on the cycle stability of a cathode half-cell at high temperature over 100 °C. For this purpose, a conventional LiFePO4 cathode composed of polyvinylidene fluoride (PVDF) (KUREHA, #1120) as binder and acetylene black (AB) as the conductive additive. We found that the rate property of the LiFePO4half-cells were much improved over 85 °C and also the cycle performance of the cells over 100 °C were much depend on the kind of cation in ILs. Acknowledgements A part of this work was supported by the R&D project for Li batteries by NEDO of Japan (Li-EAD) and Advanced Low Carbon Technology Research and Development Program (ALCA) of Japan Science and Technology Agency (JST). Reference [1] H. Matsumoto, in Electrolytes for Lithium-ion Batteries, eds. T. R. Jow, K. Xu, O. Borodin and M. Ue, Springer, 2014, ch.4 and references therein.

Biodegradability of 27 pyrrolidinium, morpholinium, piperidinium, imidazolium and pyridinium ionic liquid cations under aerobic conditions

The chemical and thermal stability of ionic liquids (ILs) makes them interesting for a large variety of applications in nearly all areas of the chemical industry. However, this stability is often reflected in their recalcitrance towards biodegradation, which comes with the risk of persistence when they are released into the environment. In this study we carried out a systematic investigation of the biodegradability of pyrrolidinium, morpholinium, piperidinium, imidazolium and pyridinium-based IL cations substituted with different alkyl or functionalised side chains and using halide counterions. We examined their primary degradability by specific analysis and/or their ultimate biodegradability using biochemical oxygen demand tests according to OECD guideline 301F. Biological transformation products were investigated using mass spectrometry. A comparison of the biodegradation potential of these ILs shows that for all five head groups, representatives can be found that are readily or inherently biodegradable, thus permitting the structural design of ILs with a reduced environmental hazard.

Studies on an Ionic Liquid Confined in Silica Nanopores: Change inTgand Evidence of Organic–Inorganic Linkage at the Pore Wall Surface

Ionic liquid (IL) 1-ethyl-3-methylimidazolium ethyl sulfate [EMIM][EtSO4] has been immobilized in silica matrix by using nonhydrolytic one-pot sol–gel method, with tetraethyl orthosilicate (TEOS) used as precursor and formic acid as a reagent. The glass transition temperature (Tg) of the confined IL was ∼20 °C higher than the bulk IL. The thermal stability of IL also increased upon confinement. These changes are explained on the basis of interactions between the inorganic SiO2 pore wall surface and the organic cation [EMIM]+ and anion [EtSO4]− of the ionic liquid. Quantum mechanical calculation based on DFT has been used to show that the oxygen of SiO2 interacts with the C–H of the imidazolium ring of [EMIM]+ cation and the surface Si atoms interact with S–O of the [EtSO4]− anion. The latter has led to Si–O–S linkages, which have been experimentally confirmed by FTIR studies. The silanol OH group is also likely to interact but less dominantly as compared to the earlier discussed interaction. These interac...

Effect of Heating Temperature on the Flash Point of Ionic Liquids

The ionic liquids are considered to be a green chemical because of their thermal stability and low volatility. This research investigated the flash point variation of ionic liquids after heat treatment at different temperature. Thermogravimetric analysis (TGA), Fourier Transform Infrared Spectroscopy FTIR) and Flash point analyser were used to analyze the thermal stability of ionic liquids. The ionic liquids, [C6mim] [Cl] and [C2mim] [NTf2] were selected as tested samples. The results indicated that the flash point of the ionic liquids was affected by the temperature of heat treatment, owing to the thermal decomposition of ionic liquids, therefore.

Thermal Stability of Ionic Liquids for Their Application as New Absorbents

The thermal stability of three ionic liquids (ILs) with the same anion and different lengths of imadazolium cations was investigated using thermogravimetric analysis to consider their usefulness for their potential application as absorbents in absorption heat pumps and refrigeration cycles. First, the influence of experimental conditions such as sample mass, heating rate, and atmosphere was analyzed for one of these ILs. Afterward, dynamic and isothermal studies were performed for the three ILs. From dynamic results, onset temperature has been often selected to define the thermal stability. Nevertheless, to obtain a more precise value, long-term isothermal studies at temperatures lower than the onset one were required, showing that the thermal stability decreases slightly as the length of the cations increases. Using the Arrhenius relationship, the kinetics of isothermal decomposition was also evaluated, and an upper limit for the “working” time of these ILs as potential absorbents was estimated.

Studies on mesoporous silica ionogels prepared by sol–gel method at different gelation temperatures

Ionogels (IGs), a novel group of materials having an ionic liquid entrapped in a mesoporous silica matrix, have been synthesized by a non-hydrolytic sol–gel process at different gelation temperatures (30, 0, −10 °C) using 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM][BF4] ionic liquid (IL), tetraethylortho-silicate (TEOS) as a metallic precursor and formic acid as a catalyst. The rate of gelation was lower at lower temperatures. Gelation temperature has also been found to affect (i) the densities of IGs, (ii) pore parameters of IGs like average pore diameter, pore surface area, pore volume and porosity, (iii) phase transition temperatures Tm, Tc, and Tg, (iv) thermal stability of IL and (v) vibrational spectra. The porosity of IG ingots, prepared at lower gelation temperatures (0, −10 °C) was higher. Unexpectedly, their densities were found to be higher than the IGs prepared at higher temperatures (say 30 °C). Possibly, one of the reaction products of the sol–gel process (namely, ethyl formate) could not escape the matrix due to its slow evaporation at low temperatures which resulted in their higher densities. The presence of ethyl formate in the IGs was confirmed by FTIR. The variation of the other properties of the IGs, listed above, synthesized at different gelation temperatures is also discussed and explained in the paper.

Superhydrophobic self-assembled monolayers of long-chain fluorinated imidazolium ionic liquids

Self-assembled monolayers (SAMs) of 1-long-chain fluorinated-alkyl-3-(3-triethoxysilylpropyl)-4,5-dihydroimidazolium ionic liquids (CnFtespim+X−) were fabricated via –Si–O– covalent bonds on Al substrates and the wettability of Al substrates with SAMs was studied. The water contact angles (CAs) of Al substrates coating with SAMs increase with the increase of the chain length of CnFtespim+X− and X− can be tuned by the exchange of counteranions. It was found that the effect of counteranions on the wettability of SAMs was dependent on the cations in some degree. Combining with micro- and nano-scale hierarchical structures via being treated with 4 mol L−1 HCl aqueous solution for 12.5 min, superhydrophobic Al surfaces having CA above 160° at n ≥ 6 can be obtained. The unique chemical and thermal stabilities of ionic liquids could be transferred to the Al substrate surfaces through anchoring, which should satisfy the superhydrophobic requirements of especial environments.

Formation and Thermal Stabilities Research of Ionic Liquids/α-ZrP Antibacterial Materials

Three different ionic liquids/alpha-zirconium phosphonates (IL-ZrP) composites antibacterial materials were prepared by introducing quarternary ammonium type ionic liquids (1-hexadecyl-3-methylimidazolium bromide, C(16)MIMBr; hexadecyl dimethyl benzyl ammonium chloride, C(16)HDBACCl; hexadecyl trimethyl ammonium chloride, C(16)CTACCl) into the interlayer of alpha-zirconium phosphonates (alpha-ZrP). The structure, components and thermal stability of composites was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscope (FTIR), Thermogravimetric-Fourier transform infrared spectroscope analysis (TG-FTIR). XRD patterns show that the interlayer spacing of IL-ZrP are larger than the original alpha-ZrP. It represents that the ionic liquids are intercalated into the layer of alpha-ZrP. TG-FTIR shows that the mass fraction of C(16)MIMBr, C(16)HDBACCl and C(16)CTACCl in three IL-ZrP are 53.11wt%, 50.65wt% and 51.25wt%, respectively. The onset temperatures of the decomposition for C(16)MIMBr, C(16)HDBACCl and C(16)CTACCl are 174 degrees C, 198 degrees C and 219 degrees C, while the onset temperatures of the decomposition for C(16)MIMBr-ZrP, C(16)HDBACCl-ZrP and C(16)CTACCl-ZrP are 219 degrees C, 225 degrees C and 263 degrees C. The existing of alpha-ZrP improves the thermal stability of ionic liquids. Among the three IL-ZrP, the C(16)MIMBr-ZrP has excellent antibacterial activity, (i.e. within 24 h, the minimal inhibitory concentration of C(16)MIMBr pillared alpha-zirconium phosphonates against S. aureus and E. coli is less than 19 mg/L).

Thermal stability of 1,3-disubstituted imidazolium tetrachloroferrates, magnetic ionic liquids

Thermal stability of synthesized magnetic liquids, tetrachloroferrates of 1,3-disubstitued derivatives of imidazolium, was examined. An effect of the cation structure on thermal stability of ionic liquids was considered and a mechanism of thermal destruction was suggested.

Thermal Stability of Ionic Liquids as an Electrolyte for Lithium-Ion Batteries

We have examined the thermal stability of several ionic liquids contacted with a charged cathode material Li0.5CoO2 by DSC and TG as the easy model-method to estimate the safety of ionic liquids as an electrolyte. From the results of DSC, it was found that the thermal stability depended on the type of ionic liquid, especially the chemical structure of the anion. The introduction of F atom to anion improved the thermal stability, but C=O groups in anion reduced the stability. For EMI·BF4 with Li0.5CoO2, DSC profile showed the exothermic peak from 200 degree C to 300 degree C and TG profile showed the weight loss in the same temperature area, though neither exothermic peak nor weight loss was observed up to 350 degree C for sole EMI·BF4. From the analysis of generated gas, the main gas was CO2 in the area of exothermic heat.

Preparation of Nylon‐6 Particles in Ionic Liquids

AbstractSummary: Utilizing the thermal stability of ionic liquid, micrometer‐sized Nylon‐6 particles were successfully prepared by hydrolytic polymerization of ε‐caprolactam at high temperature with polyvinyl pyrrolidone as stabilizer in ionic liquids, 1‐butyl‐3‐methyl imidazolium tetrafluoroborate, [Bmim][BF4] and N,N‐diethyl‐N‐methyl‐N‐(2‐methoxyethyl)ammonium bis(trifluoro‐methanesulfonyl)amide, [DEME][TFSA]. The obtained particles had a unique shape because Nylon‐6 is a crystalline polymer. Viscosity‐average molecular weights of Nylon‐6 prepared in [Bmim][BF4] and [DEME][TFSA] at 180 °C for 48 h were 4200 and 2200, respectively.

Thermal decomposition of allyl-imidazolium-based ionic liquid studied by TGA–MS analysis and DFT calculations

Thermal stability of ionic liquids (ILs) is of great significance for their applications in dissolving cellulose at elevated temperature. A novel ionic liquid, 1-allyl-3-methylimidazolium chloride ([Amim]Cl), was found to be a powerful solvent for cellulose. However, the study about long-term isothermal stability, thermal decomposition mechanism and decomposition products of [Amim]Cl are scarce. Herein, we studied the thermal stability and degradation mechanism of [Amim]Cl using isothermal thermogravimetric analysis (TGA) experiments and density functional theory (DFT) calculations. The weight loss of [Amim]Cl at 100 °C under air atmosphere within 15 days was only 1.9% and [Amim]Cl after long-term heating also had dissolving capability of cellulose, indicating that [Amim]Cl has high thermal stability and can be long-term used at the dissolving temperature of cellulose. Both TGA experiments and DFT calculations revealed [Amim]Cl decomposed along two channels and the main pyrolysis products of the proposed mechanisms were detected using thermogravimetric technique coupled with mass spectrometry (TGA–MS).

Thermal stability of ionic liquids assessed by potentiometric titration

The long-term thermal stability of imidazolium-based ionic liquids is addressed here. We have found that potentiometric titration is a precise, low-cost and quick analytical method to assess the quality changes occurring during the thermal aging of ionic liquids. Using this protocol, we have discovered that imidazolium-based ionic liquids start to decompose, to a small extent, at much lower temperatures than those inferred from thermogravimetric analysis.