Tf 2N Research Articles

PREDIÇÃO DA ENERGIA DE ATIVAÇÃO DE FLUXO VISCOSO DOS LÍQUIDOS IÔNICOS IMIDAZÓLICOS [HMIM][PF6] E [BMIM][TF2N

The ionic liquids have attracted great interest especia lly in relation to potencial to replace conventiona l organic solvents in various processes. This work aimed to predict values for the activatio n energy for viscous flow of imidazolium ionic liquids 1-methyl-3-hexylimidazoli um hexafluorophosphate ((HMIM)(PF 6)) and 1-butyl-3- methylimidazolium bis(trifluorosulfonyl)imide ((BMIM)(Tf 2N)). For this purpose, there was a linear regressio n analysis of experimental data of the viscosity of each imida zolium ionic liquid according to the temperature at 0.1MPa. These experimental data were found in the literature. The values of activation energy for viscous flow were equal to 46.6211kJ.mol-1 for (HMIM)(PF 6) and 29.1744kJ.mol -1 for (BMIM)(Tf 2N). In both cases, the correlation coefficients

Liquid–liquid extraction of toluene from n-heptane using binary mixtures of N-butylpyridinium tetrafluoroborate and N-butylpyridinium bis(trifluoromethylsulfonyl)imide ionic liquids

Liquid–liquid extraction of toluene from heptane using binary mixtures of the ionic liquids N-butylpyridinium bis(trifluoromethylsulfonyl)imide ([bpy][Tf 2N]) and N-butylpyridinium tetrafluoroborate ([bpy][BF 4]) have been investigated at 313.2 K and atmospheric pressure. On the basis of the experimental liquid–liquid equilibrium data for the pseudoternary system n-heptane + toluene + mixed ionic liquids, the values of the distribution ratio and selectivity were calculated and compared to those for the pure ionic liquids, for sulfolane, and those predicted by an ideal mixing rule. The results showed that the use of binary mixture of {[bpy][BF 4] + [bpy][Tf 2N]} at a mole solvent composition of 0.7 for [bpy][BF 4] improves both the distribution ratio of toluene and the selectivity with respect to those of sulfolane. Thus, this mixed ionic liquid could be considered an environmentally benign alternative solvent for the aromatic extraction process.

Laser-induced fluorescence and infrared spectroscopic studies on the specific solvation of tris(1-(2-thienyl)-4,4,4-trifluoro-1,3-butanedionato)europium(III) in an ionic liquid

The extraction constant and the two-phase stability constant ( K D,M β 3) of tris(2-thenoyltrifluoroacetonato)europium(III) between 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C 4mim][Tf 2N]) as an ionic liquid and an aqueous phase were determined by considering the extraction equilibria including anionic tetrakis(2-thenoyltrifluoroacetonato)europate(III). Specific solute–solvent interactions between the neutral Eu(III) chelate and [C 4mim][Tf 2N] molecules were revealed from the relationships between the distribution constant of the enol form of 2-thenoyltrifluoroacetone (Htta) as a proton chelate and the distribution constant ( K D,M) of the neutral Eu(III) chelate because the [C 4mim][Tf 2N] system gave the high K D,M β 3 value compared with those in conventional molecular solvents such as benzene and 1,2-dichloroethane. The coordination environment of Eu 3+ in the neutral Eu(III) chelate in [C 4mim][Tf 2N] was investigated by time-resolved laser-induced fluorescence spectroscopy and infrared absorption spectroscopy. Both methods consistently indicated that not only the Eu(III) chelate extracted but also Eu(tta) 3(H 2O) 3 synthesized as a solid crystal were almost completely dehydrated in [C 4mim][Tf 2N] saturated with water. Consequently, the higher K D,M or extractability of the neutral Eu(III) chelate in the [C 4mim][Tf 2N] system can be ascribed to the dehydration of the Eu(III) chelate, which is caused by the specific solvation with [C 4mim][Tf 2N] molecules.

Ionic liquids as novel spectroscopic solvents for Eu(III)-containing complex

Novel soft materials, Eu(III)-containing complex dissolved in [C 8mim][X] (X=Cl −, PF 6 − and Tf 2N −) ionic liquids, were synthesized. FT-IR and elementary analysis of complex proved that the molecular formula is [C 8mim][Eu(TTA) 4]. The complex and ionic liquids had high thermal stability according to TGA. The photoluminescence spectra showed that the [C 8mim][Eu(TTA) 4] exhibited typical red emission deriving from 5D 0– 7F 2 transition. After dissolving the complex in [C 8mim][X] (X=Cl −, PF 6 − and Tf 2N −) ionic liquids, the luminescence intensity decreased in the following order: [C 8mim][Tf 2N]≈[C 8mim][PF 6]>[C 8mim][Cl]. This was because Tf 2N − and PF 6 − anions had larger molecular volume and weaker coordination ability than Cl −.

Ionic liquid membranes for carbon dioxide–methane separation

The transport of carbon dioxide and methane in polymer containing ionic liquid was studied by a dynamic gas permeation method. Poly(vinylidene fluoride-co-hexafluoropropylene) polymeric membrane (Viton) and two ionic liquids 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([hmim][Tf 2N]) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf 2N]) were used for preparation of ionic liquid membranes (ILM) with different ionic liquid amounts (from 0 to 80 wt%). For the better understanding of transport mechanism through ionic liquid membranes it is very useful to know also transport properties of pure ionic liquids and pure polymeric material. The gas transport through pure ionic liquid was determined indirectly, by means of the gas transport measurement through two special types of membranes: “sandwich arrangement” and “support arrangement”. The dependencies of the separation factor and gas fluxes on the ionic liquid amounts in ionic liquid membranes were determined. The gas permeability increased with the ionic liquid [emim][Tf 2N] content in the membrane, the permeability for the membranes with [hmim][Tf 2N] exhibits the maximum for IL concentration of 70 wt%. Ideal separation factor CO 2/CH 4 was low for small contents of ILs in membranes (0–15 wt%), around 7 for [emim][Tf 2N] and 8 for [hmim][Tf 2N] but for higher contents (30–75 wt%) it was approximately constant, 15 for [emim][Tf 2N] and 12 for [hmim][Tf 2N]. Very interesting is the comparison of carbon dioxide permeability, it increases in the series: polymer, ionic liquid and ionic liquid membrane. Although the transport properties values of ILM were expected to be in the middle of the ionic liquid and the polymer from which were formed, surprisingly the obtained transport properties of ILM are much better than those for the pure components. For example, the carbon dioxide permeability for the ionic liquid membrane with 70 wt% of [hmim][Tf 2N] is almost thousand times higher than for the pure polymer, and hundred times higher than for the ionic liquid. This fact indicates that the mechanism of the transport in ionic liquid membranes has to be different from the transport mechanisms in an ionic liquid. An explanation could be that “new transport pores” are created between polymer chains and an ionic liquid.

Simultaneous solubility of carbon dioxide and hydrogen in the ionic liquid [hmim][Tf 2N]: Experimental results and correlation

The solubility of a single gas as well as the simultaneous solubility of several gases in an ionic liquid is of great interest in many areas of chemical engineering, particularly in heterogeneous catalysis. One of the most interesting features involved in the study of the simultaneous solubility of several gases in a pure ionic liquid is the difference between experimental data and predictions for the simultaneous solubility (based on experimental data for the solubility of the single gases). The well soluble gas might act as a cosolvent or as an antisolvent for a sparsely soluble second gas. New experimental results and a correlation are presented for the simultaneous solubility of hydrogen (i.e., a sparsely soluble gas) and carbon dioxide (a well soluble gas) in the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf 2N]) at temperatures between 293 K and 373 K and pressures up to about 9.2 MPa. The experimental results reveal that carbon dioxide acts as a cosolvent for hydrogen in that particular ionic liquid. A correlation shows that the cosolvency effect can be modeled by considering interaction parameters between hydrogen and carbon dioxide in liquid [hmim][Tf 2N]. The correlation can also be used to quantify that cosolvency effect: one mole of carbon dioxide in 1000 g of [hmim][Tf 2N] increases the solubility of (small amounts of) hydrogen by about 20%.

High-pressure phase behavior of binary mixtures containing ionic liquid [HMP][Tf 2N], [OMP][Tf 2N] and carbon dioxide

This paper presents bubble-point pressure data for CO 2 in ionic liquids 1-hexyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([HMP][Tf 2N]) and 1-octyl-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([OMP][Tf 2N]) at pressures up to approximately 62 MPa and temperatures between 303.15 and 373.15 K. The solubility of CO 2 in ionic liquids was measured with a high-pressure variable-volume view cell. At high CO 2 concentrations in ionic liquids, the equilibrium pressure increased sharply with increasing CO 2 concentrations while the solubility of CO 2 in the ionic liquids decreased commensurate to increases in temperature. We have observed that in the [Tf 2N] anion-based ionic liquids, the shorter the alkyl group chain in cation is, the larger the solubility of CO 2 in ionic liquid become. The experimental data for the CO 2 + ionic liquid system were relatively well correlated using the Peng–Robinson equation of state.

CO 2 separation membranes using ion gels by self-assembly of a triblock copolymer in ionic liquids

CO 2 separation ion gel membranes with compatible permselectivity for supported ionic liquid membranes (SILMs) and good mechanical stability were developed using a triblock copolymer that self-assembles in CO 2-selective ionic liquids (ILs). Three ion gels with 1-n-hexyl-3-methylimidazolium ([hmim]) cation base, each containing different anions ([Tf 2N −], [BF 4 −], and [PF 6 −]) and a small amount of poly(styrene-block-ethylene oxide-block-styrene) (SEOS) triblock copolymer were prepared and characterized using differential scanning calorimetry and wide-angle X-ray diffraction analysis. Mechanically stable composite membranes made with three different ion gels were prepared by the self-assembly of IL/SEOS on the surface of the nylon support membrane and characterized by the measurement of their CO 2 separation performance. The ideal CO 2/CH 4 separation factors were 9.0, 9.5 and 9.9 for the ion gel membranes containing [hmim][Tf 2N], [hmim][BF 4] and [hmim][PF 6], respectively. These values are consistent with or higher than those of SILMs due to the microstructure formation inside the ion gels.

Recovery of erythromycin from aqueous solutions with an ionic liquid and high-pressure carbon dioxide

Recovery of erythromycin from aqueous solutions was studied in two steps: (i) single- and multi-stage extraction of erythromycin from an aqueous solution with a hydrophobic ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide [BMPyrrol][Tf 2N], as a function of pH and feed to solvent volume ratio, and (ii) high-pressure CO 2 extraction of erythromycin from the ionic liquid, as a function of pressure, temperature and presence of water. Furthermore, data on the mutual solubilities of the hydrophobic ionic liquid and water, as well as on the solubility of erythromycin in [BMPyrrol][Tf 2N], were obtained. The chemical stability of erythromycin in water-free and water saturated ionic liquid was tested. These results allowed the evaluation of the coupling of liquid–liquid and high-pressure CO 2 extractions.

Iodide/triiodide electrochemistry in ionic liquids: Effect of viscosity on mass transport, voltammetry and scanning electrochemical microscopy

The electrochemistry of I −/I 3 − was studied in ionic liquids using a combination of cyclic voltammetry, chronoamperometry and scanning electrochemical microscopy (SECM). The electrolytes were 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [C n C 1Im][Tf 2N], ionic liquids (where n = 2, 4 and 8) and I − was typically added at a concentration of approximately 11 mM. During cyclic voltammetry, two sets of peaks were observed in each ionic liquid due to oxidation and reduction of the I −/I 3 − redox couple and oxidation/reduction of the I 3 −/I 2 redox couple. The diffusion coefficients of I − and I 3 −, as determined using chronoamperometry, increased with increasing temperature and decreased with increasing ionic liquid viscosity. The effect of ionic liquid viscosity on ultramicroelectrode (UME) voltammetry was also determined using the I −/I 3 − redox couple. Steady-state behaviour was observed at 1.3 μm UMEs at slow voltammetric scan rates and steady-state SECM feedback approach curves were also obtained at a 1.3 μm Pt SECM tips, provided that the tip approach speed was sufficiently low.

Photoinduced intermolecular electron transfer in a room temperature imidazolium ionic liquid: An excitation wavelength dependence study

In this work we have reported the photoinduced intermolecular electron transfer reaction from N, N-dimethylaniline to different Coumarin dyes in a neat room temperature imidazolium ionic liquid, 1-ethyl-3-methylimidazolium-bis (trifluoromethylsulfonyl) imide ([Emim][Tf 2N]) and observed a difference in electron transfer rate with the variation of excitation wavelengths. We have also observed an excitation wavelength dependent solvation dynamics in this ionic liquid media. The excitation wavelength dependence is attributed to the presence of structural heterogeneity in this neat ionic liquid media. The electron transfer rate vs free energy correlation curve show a retardation in the electron transfer rate at higher free energy region.

Study on immobilized liquid membrane using ionic liquid and PVDF hollow fiber as a support for CO 2/N 2 separation

This study focuses on improving the CO 2 permeability and stability of the liquid membrane. To improve permeability, polymeric hollow fiber support with a high effective area per unit volume were prepared with various dope composition as a support; to improve stability, the effects of varying the structure of the support and immobilization conditions were observed and analyzed. For the experiment, 1-ethyl-3-methylimidazolium-bis(trifluoromethylsulfonyl) imide ([emim][Tf 2N]) and polyvinylidene fluoride (PVDF) were used. For immobilization of the [emim][Tf 2N], the liquid was diluted to 40 vol.% in methanol and immobilized liquid membranes (ILMs) were prepared as gas permeation modules. The prepared ILM module was characterized by single gas permeation of CO 2 and N 2 according to feed pressure at atmosphere temperature. All of prepared modules were observed with high CO 2 permeability of over 2600 barrer, respectively. However, stability on pressure was affected by support structure.

Novel mixed matrix membranes based on polymerizable room-temperature ionic liquids and SAPO-34 particles to improve CO 2 separation

A mixed-matrix membrane containing three components consisting of a solid polymerized room-temperature ionic liquid (poly(RTIL)), a liquid RTIL, and a zeolite material was previously investigated. This membrane showed an improvement in CO 2/CH 4 separation over the neat poly(RTIL)–RTIL composite membrane without the zeolite component. It was hypothesized that the RTIL served as “wetting agent,” improving the adhesion between the poly(RTIL) (a charged organic polymer) and zeolite particles (charged inorganic particles). In this article, a detailed study of the CO 2 separation performance of this 3-component MMM system is presented, along with results showing how the system can be optimized or tuned. Specifically, this study focuses on the effect of varying SAPO-34 and RTIL loadings on the separation performance of the 3-component MMMs. 3-Component MMMs containing [emim][Tf 2N] and styrene-based poly(RTIL)s with various loadings of SAPO-34 and various compositions of RTILs and poly(RTIL)s were prepared. Another type of poly(RTIL), which has a longer n-alkyl substituent and a polyolefin backbone was also investigated, in addition to the initial styrene-based poly(RTIL). The single gas permeation of various compositions and types of these 3-component MMMs were investigated. The results show that increasing the amount of RTIL in the 3-component MMM increases the CO 2 permeability of the composite membrane. The presence of the SAPO-34 particles in the 3-component MMM improves both the CO 2/CH 4 selectivity and CO 2 permeability in comparison to the neat poly(RTIL)–RTIL composite membrane. For the 3-component MMMs based on the poly(RTIL) with an olefin backbone, the presence of the added liquid RTIL component is not mandatory, which may be due to the similarity of its structure compared to [emim][Tf 2N]. In this paper, we also propose a potential molecular arrangement of the poly(RTIL), RTIL, and SAPO-34 particles in the 3-component MMMs.

Supported hydrophobic ionic liquid on nano-silica for adsorption of lead

The hydrophobic character incorporated into 1-methyl-3-octylimidazolium bis(trifluoromethyl-sulfonyl)imide [OMIM +Tf 2N −] based on both the anion and cation natures was employed to develop a novel solid phase extraction medium based on physical adsorption approach. Two modified nano-silica sorbents were synthesized via direct immobilization of [OMIM +Tf 2N −] on the surface of active nano-silica [NSi-OH] and amino nano-silica [NSi-NH 2] for the formation of [NSi-OH-OMIM +Tf 2N −] and [NSi-NH 2-OMIM +Tf 2N −], respectively. Surface characterization was confirmed by TGA, FT-IR and SEM. The surface coverage values were identified in the range of 1.223–1.272 mmol g −1. Modified sorbents were extensively studied and characterized by their high similarity and affinity for lead extraction without the need for chelating intermediate. Excellent sorption capacity values (0.5–0.9 and 0.8–1.3 mmol g −1) of lead were determined in pH 1–7. Other factors such as reaction contact time, sorbent dose, initial metal ion concentration and interfering ions were studied to spot more light on the sorption capability of loaded hydrophobic ionic liquid for application in the solid phase extraction mode. These sorbents were successfully implemented for removal and preconcentration of lead from various water samples via application of a multi-stage micro-column giving rise to percentage recovery values of lead in the range of 98.0–100.0 ± 3.0–4%.

Density, viscosity, and electrical conductivity of N-methoxymethyl- N-methylpyrrolidinium bis(trifluoromethanesulfonyl)amide

The densities, viscosities, and electrical conductivities of the ionic liquid N-methoxymethyl- N-methylpyrrolidinium bis(trifluoromethanesulfonyl)amide, [Pyr 1,1O1][Tf 2N] have been measured with expanded uncertainties of ±0.05 kg m −3, ±2%, and ±2% over a wide temperature range between 273.15 and 363.15 K at atmospheric pressure. The temperature dependence of the viscosity and conductivity was analyzed by the Litovitz and Vogel–Fulcher–Tammann equations. The effect of the methoxymethyl group instead of the propyl one on such physicochemical properties is discussed in comparison with the similar analogue, N-methyl- N-propylpyrrolidinium bis(trifluoromethanesulfonyl)amide, [Pyr 1,3][Tf 2N].

Evaporation of ionic liquids at atmospheric pressure: Study by ion mobility spectrometry

A conventional ion mobility spectrometry (IMS) was used to study atmospheric pressure evaporation of seven pure imidazolium and pyrrolidinium ionic liquids (ILs) with [Tf 2N], [PF 6], [BF 4] and [fap] anions. The positive drift time spectra of the as-received samples measured at 220 °C exhibited close similarity; the peak at reduced mobility K 0 = 1.99 cm 2 V −1 s −1 was a dominant spectral pattern of imidazolium-based ILs. With an assumption that ILs vapor consists mainly of neutral ion pairs, which generate the parent cations in the reactant section of the detector, and using the reference data on the electrical mobility of ILs cations and clusters, this peak was attributed to the parent cation [emim]. Despite visible change in color of the majority of ILs after the heating at 220 °C for 5 h, essential distinctions between spectra of the as-received and heated samples were not observed. In negative mode, pronounced peaks were registered only for ILs with [fap] anion.

Nonenzymatic glucose sensor based on flower-shaped Au@Pd core–shell nanoparticles–ionic liquids composite film modified glassy carbon electrodes

A novel nonenzymatic glucose sensor based on flower-shaped (FS) Au@Pd core–shell nanoparticles–ionic liquids (ILs i.e., trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl) imide, [P(C 6) 3C 14][Tf 2N]) composite film modified glassy carbon electrodes (GCE) was reported. The Au@Pd nanocatalysts were prepared by seed-mediated growth method, forming the three-dimensional FS nanoparticles, where tens of small Pd nanoparticles (∼3 nm) aggregated on gold seeds (∼20 nm). The FS Au@Pd nanoparticle was a good candidate for the catalytic efficiency of nanometallic surfaces because of its flower-shaped nature, which has greater adsorption capacity. XPS analysis and zeta potential indicated that the surface of Pd atoms is positively charged, profiting the oxidation process of glucose. And ILs acted as bridge connecting Au@Pd one another and bucky gel as platform within the whole nanocomposite. So the modified electrode has higher sensitivity and selectivity owing to intrinsic synergistic effects of this nanocomposite. Amperometric measurements allow observation of the electrochemical oxidation of glucose at 0.0 V (vs. Ag/AgCl), the glucose oxidation current is linear to its concentration in the range of 5 nM–0.5 μM, and the detection limit was found to be 1.0 nM (S/N = 3). The as-prepared nonenzyme glucose sensor exhibited excellent stability, repeatability, and selectivity.

Ionic liquids in electrosynthesis and characterization of a polyazulene-fullerene composite

Polyazulene (PAz) was electrosynthesized in the ionic liquid N,N-butyl-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP][Tf 2N]) and characterized using electrochemical methods. By using [BMP][Tf 2N] as the electrolyte we obtained films with improved electrochemical and morphological properties compared to films electrosynthesized in an acetonitrile-based electrolyte solution. Composite films consisting of drop cast C 60 and electrosynthesized PAz were also investigated in [BMP][Tf 2N] using electrochemical methods, UV–vis and SEM and the results were compared to similar films prepared in acetonitrile. The use of ionic liquids made it possible to study the redox reactions of C 60 at room-temperature and in an extended cathodic potential range. In comparison to pure PAz the presence of C 60 in the composite film improved the charge storing ability. Electrosynthesis in [BMP][Tf 2N] resulted in composite films with a lower degree of charge trapping compared to composite films synthesized in organic media.

Effects of temperature and anion species on CO 2 permeability and CO 2/N 2 separation coefficient through ionic liquid membranes

The permeability of carbon dioxide (CO 2) through imidazolium-based ionic liquid membranes was measured by a sweep gas method. Six species of ionic liquids were studied in this work as follows: [emim][BF 4], [bmim][BF 4], [bmim][PF 6], [bmim][Tf 2N], [bmim][OTf], and [bmim][dca]. The ionic liquids were supported with a polyvinylidene fluoride porous membrane. The measurements were performed at T = (303.15 to 343.15) K. The partial pressure difference between feed and permeate sides was 0.121 MPa. The permeability of the CO 2 increases with temperature for the all ionic liquid species. Base on solution diffusion theory, it can be explained that the diffusion coefficient of CO 2 in an ionic liquid affects the temperature dependence more strongly than the solubility coefficient. The greatest permeability was obtained with the [bmim][Tf 2N] membrane. The membrane of [bmim][PF 6] presents the lowest permeability. The separation coefficient between CO 2 and N 2 through the ionic liquid membranes was also investigated at the volume fraction of CO 2 at feed side 0.10. The separation coefficient decreases with the increase of temperature for the all ionic liquid species. The membrane of [emim][BF 4] and [bmim][BF 4] gives the highest separation coefficient at constant temperature. The lowest separation coefficient was obtained from [bmim][Tf 2N] membrane which presents the highest permeability of CO 2.

Combination of dispersive liquid–liquid microextraction and flame atomic absorption spectrometry for preconcentration and determination of copper in water samples

A simple and rapid dispersive liquid–liquid microextraction procedure based on an ionic liquid (IL-DLLME) was developed for the determination of trace amounts of copper (Cu 2+) by flame atomic absorption spectrometry (FAAS). In this work, a small amount of an IL 1-hexyl-3-methylimmidazolium bis(trifluormethylsulfonyl)imid ([Hmim][Tf 2N]) as an extraction solvent was dissolved in acetone as a disperser solvent and then the binary solution was rapidly injected by a syringe into the water sample containing Cu 2+, which were complexed by 4,4′-bis(dimethylamino)thiobenzophenone (TMK). After preconcentration, the settled IL-phase was dissolved in 40 μL of ethanol and aspirated into the flame atomic absorption spectrometer (FAAS) using a home-made microsample introduction system. Injection of 50 μL volumes of analyte into an air–acetylene flame provided very sensitive spike-like and reproducible signals. Some important IL-DLLME parameters, such as amount of the ionic liquid, chelating reagent concentration, pH and salt concentration were inspected by a (2 4) full factorial design to identify the most important parameters and their interactions. Under optimum conditions, the calibration graph was linear in the range of 2–50 μg L −1 with a limit of detection of 0.45 μg L −1. The relative standard deviation was 3.3% (n = 5).