Tricyanomethanide-based Ionic Liquids Research Articles

Correction to “Experimental and CPA EoS Description of the Key Components in the BTX Separation from Gasolines by Extractive Distillation with Tricyanomethanide-Based Ionic Liquids”

Correction to “Experimental and CPA EoS Description of the Key Components in the BTX Separation from Gasolines by Extractive Distillation with Tricyanomethanide-Based Ionic Liquids”

Accessing Lanthanide Tricyanomethanide Coordination Polymers Using Ionic Liquids

In contrast to alkaline, alkaline earth, and transition metals, tricyanomethanide complexes of f-elements are largely underexplored mainly due to synthetic challenges originating from the harder Lewis acidic character of the trivalent cations; only one crystal structure of an f-element-tricyanomethanide complex has ever been reported. Here, we report that by using the tricyanomethanide-based ionic liquids (ILs) 1-butyl-4-methylpyridinium tricyanomethanide ([C4mpyrid][TCM]) or 1-ethyl-3-methylimidazolium tricyanomethanide ([C2mim][TCM]), we have identified a way to begin building a library of 1D and 2D lanthanide/tricyanomethanide coordination polymers, although not yet in an optimized, controllable fashion. Saturation of NdX3·6H2O (X = Cl– or [NO3]−) over 100 °C in [C4mpyrid][TCM] or [C2mim][TCM] followed by slow cooling allowed for the crystallization of [C2mim]n[Nd(NO3)2(μ3-TCM)(μ2-TCM)(OH2)]n (1), [C4mpyrid]2n[Nd(μ2-Cl)Cl2(μ2-TCM)(TCM)(OH2)]n (2), [C4mpyrid]n[Nd(μ2-TCM)2(TCM)2(OH2)3]n (3), and [C4mpyrid]n[NdCl2(μ2-TCM)2(OH2)2]n (4) as anionic chains (2, 4) or layers (1, 3). Compound 3 could be isolated either by saturation and heating of Nd(NO3)3·6H2O or by reheating the reaction mixture leading to 2. The use of [TCM]−-based ILs as solvent and sources of the coordinating ligand provides a method to promote f-element-[TCM]− complexation without the use of competing O-donor solvents or high temperatures, potentially opening a new route to structurally characterize [TCM]− complexes of the entire lanthanide series. Although these products were not synthesized in high yields, their isolation provides clues on how to modify and optimize the syntheses to obtain specific f-element-[TCM]− targets. This, in turn, should ultimately lead to dramatic diversification of the body of f-element-[TCM]− complexes available for study.

Thermodynamic Properties of Tricyanomethanide-Based Ionic Liquids with Water: Experimental and Modelling

Thermodynamic Properties of Tricyanomethanide-Based Ionic Liquids with Water: Experimental and Modelling

Density, viscosity, and high-pressure conductivity studies of tricyanomethanide-based ionic liquids

In this paper, conductivity and viscosity of 1-alkyl-3-methylimidazolium tricyanomethanide series ([CnC1im][TCM], where n = 2, 4, 6, and 8) were measured and analyzed in the broad temperature range covering supercooled and normal liquid states at ambient pressure. The density at ambient pressure up to 363.15 K was also investigated. From these experimental data, the Walden plots for the studied ionic liquids were obtained and dependencies for all tested samples lie below the reference line for fully dissociated 0.01 mol·dm−3 KCl. The temperature dependence of viscosity revealed clear crossover from one Vogel–Fulcher–Tamman behavior to another at some intermediate temperature that increases with the alkyl chain length of the cation and we discovered that all examined ILs are fragile glass formers. Additionally, the high-pressure conductivity data up to 600 MPa of three homologues (n = 4, 6, and 8) were reported and correspondingly the dynamic modulus and pressure coefficient of glass transition temperature were analyzed. The results demonstrated that the former increases with the alkyl chain length while the latter is independent of alkyl chain length.

Experimental and CPA EoS Description of the Key Components in the BTX Separation from Gasolines by Extractive Distillation with Tricyanomethanide-Based Ionic Liquids

Two tricyanomethanide-based ionic liquids (ILs), namely 1-ethyl-3-methylimidazolium tricyanomethanide ([C2C1im][TCM]) and 1-butyl-4-methylpyridinium tricyanomethanide ([4-C4C1py][TCM]) have been re...

High pressure density of tricyanomethanide-based ionic liquids: Experimental and PC-SAFT modelling

Tricyanomethanide-based ionic liquids (ILs) are, probably, the most interesting ILs for separation purposes considering their low viscosity and high thermal stability, but mainly due to their enhanced performance in a wide number of applications. However, the scarce high pressure density data (ρpT) limits the development of robust models for process simulation implementation and consequently process development. In this work, high pressure density data of 1-ethyl-3-methylimidazolium tricyanomethanide ([C2C1im][TCM]) and 1-butyl-4-methylpyridinium tricyanomethanide ([4-C4C1py][TCM]) are reported in a wide range of temperature (283–363) K and pressure (0.1–95) MPa. The new ρpT data and its derivative properties, namely isothermal compressibility (kT) and isobaric thermal expansivity (αP), of the studied ILs and that reported for the 1-butyl-3-methylimidazolium tricyanomethanide ([C4C1im][TCM]), were successfully modelled using the Perturbed-Chain Statistical Association Fluid Theory (PC-SAFT). New molecular parameters for the tricyanomethanide-based ILs are here proposed allowing a good description of the studied properties while assessing the well-known non-volatile character of the ILs.

Thorough studies of tricyanomethanide-based ionic liquids - the influence of alkyl chain length of the cation.

The glassy, supercooled, and normal liquid states of the 1-alkyl-3-methylimidazolium tricyanomethanide series [CnC1im][TCM] (n = 2, 4, 6, 8, and 16) were investigated by dielectric and mechanical (rheological) experiments supplemented by X-ray diffraction. The conductivity relaxation was found to be accompanied by a pronounced secondary relaxation. However, based on ambient and high-pressure results as well as the coupling model, we assumed that the latter one can not be classified as Johari-Goldstein relaxation. Moreover, the studies on the nanoscale organization of ionic liquids indicated that 1-alkyl-3-methylimidazolium tricyanomethanide ILs begin to form nanoscale aggregates when the alkyl chain of the cation has six carbon atoms.

Toward Modeling the Aromatic/Aliphatic Separation by Extractive Distillation with Tricyanomethanide-Based Ionic Liquids Using CPA EoS

Extractive distillation using tricyanomethanide-based ionic liquids (ILs) has been shown to be a promising and feasible process for effectively separate aromatics from pyrolysis gasolines. The high performance of these mass agents has been reported by evaluating simple synthetic n-heptane/toluene binary mixtures, on a wide temperature and solvent to feed (S/F) ratio ranges. However, industrial streams are much more complex with the presence of other aromatic and aliphatic compounds, like benzene, xylenes, and shorter and longer linear alkanes, creating further difficulties to the separation and thus must be studied. This work covers the phase equilibrium characterization of {n-hexane + benzene + IL} and {n-octane + p-xylene + IL} ternary systems with two tricyanomethanide-based ILs, namely 1-ethyl-3-methylimidazolium tricyanomethanide ([C2C1im][TCM]) and 1-butyl-4-methylpyridinium tricyanomethanide ([4-C4C1py][TCM]), addressing also the phase characterization of the corresponding {hydrocarbon + IL} binary...

Liquid–liquid extraction of sulfur compounds from heptane with tricyanomethanide based ionic liquids

Liquid–liquid phase equilibrium (LLE) data for the {tricyanomethanide-based ionic liquid (1) + tiophene, or benzothiophene (2) + heptane (3)} ternary systems were experimentally determined at T = 308.15 K and at pressure p = 0.1 MPa. In this work three ILs, that is: 1-butyl-1-methylmorpholinium tricyanomethanide, [BMMOR][TCM], 1-butyl-1-methylpyrrolidinium tricyanomethanide, [BMPYR][TCM] and 1-hexyl-1-methylmorpholinium tricyanomethanide, [HMMOR][TCM] have been investigated. The high solubility of sulfur compounds and practically complete immiscibility of heptane with the tested ionic liquids have been observed. The selectivity, S12 and solute distribution ratio, k12 derived from the experimental equilibrium data, were calculated and used to determine the efficiency of these ionic liquids as solvents for the extraction of sulfur compounds from model fuels. The experimental results have been compared to literature data for other tricyanomethanide-based ILs and were discussed in terms of the selectivity and solute distribution ratio of separation of related systems. The NRTL equation was successfully used to correlate the experimental tie-lines. The average root mean square (RMSD) of the phase composition was less than 0.8%. Additionally, the oxidative-extractive desulfurization of model fuels has been studied using tricyanomethanide-based ionic liquid (IL): [BMMOR][TCM] and [BMPYR][TCM] and deep eutectic solvent (DES): ([BMMOR] [Br] + diethylene glycol). Model liquid fuel was prepared by dissolving benzothiophene in octane, 500 ppm of sulfur. Oxidation was achieved by adding hydrogen peroxide and acetic acid to the mixture. Different parameters such as a type of extractant, extraction time, and oxidant to sulfur molar ratio and temperature were optimized. The addition of oxidizing agent improves the efficiency of sulfur extraction and the highest extraction efficiency, equal to 69.1%, was obtained for [BMMOR][TCM] at T = 318.15 K.

Toluene/n-Heptane Separation by Extractive Distillation with Tricyanomethanide-Based Ionic Liquids: Experimental and CPA EoS Modeling

This work covers the phase equilibrium characterization of systems containing n-heptane, toluene, and two tricyanomethanide-based ionic liquids (ILs), 1-ethyl-3-methylimidazolium tricyanomethanide ([C2C1im][TCM]) and 1-butyl-4-methylpyridinium tricyanomethanide ([4-C4C1py][TCM]). Aiming at evaluating these ILs for the n-heptane/toluene extractive distillation, the vapor–liquid–liquid equilibria (VLLE) and vapor–liquid equilibria (VLE) were determined by headspace-gas chromatography (HS-GC) in the whole composition range at temperatures from 323.2 to 423.2 K and solvent to feed (S/F) ratios of 1, 5, and 10. Experimental results were modeled with the Cubic Plus Association (CPA) Equation of State (EoS). ILs’ molecular parameters were regressed through density and heat capacity data and further used to describe the binary and ternary mixtures phase equilibria. Extractive distillation with ILs stands as a powerful approach for the dearomatization of liquid fuels, whereas the combination of HS-GC methodology a...

Carbon dioxide solubilities in tricyanomethanide-based ionic liquids: Measurements and PC-SAFT modeling

This work reports the measurements of the solubility of carbon dioxide (CO2) in three tricyanomethanide based ionic liquids (ILs) constituted by different cations: 1-butyl-3-methylimidazolium, 1-butyl-4-methylpyridinium, 1-butyl-1-methylpyrrolidinium in order to investigate the effect of the cation on the solubility. The solubility of CO2 have been determined using high-pressure variable volume cell in a range of temperature from T = (292.13–367.85) K and pressure up to 121.6 bars. A high solubility of CO2 in the 1-butyl-4-methylpyridinium tricyanomethanide was observed in comparison with the other cation. It was found that the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) may be used to represent with good accuracy the experimental data of CO2 solubility in tricyanomethanide based ionic liquid.

Experimental screening towards developing ionic liquid-based extractive distillation in the dearomatization of refinery streams

Abstract Ionic liquids (ILs) are potential neoteric solvents to design new advanced separation processes. Among several separation cases studied so far, the good performance of ILs regarding the dearomatization of liquid fuels, i.e. pyrolysis and reformer gasolines, has received especially attention. Indeed, a wide number of works has been done to characterize the phase equilibria for {aliphatic + aromatic + ILs} systems as well as the IL thermophysical properties, concluding in the development of a liquid-liquid extraction process. However, this technology seems not to be enough to fulfill current aromatic commercial standards nor potential incoming restrictions for aromatic content in liquid fuels as a result of its low separation effectiveness for extreme aliphatic and aromatic purification. Extractive distillation with ILs stands as a new process configuration to overcome these limitations by enhancing the aliphatic/aromatic relative volatilities. In this work, an IL experimental screening in the n-heptane/toluene separation was done to further develop this new IL-based technology. Nine ILs were tested as mass agents in a wide range of conditions, i.e. solvent to feed (S/F) ratios from 1 to 10 and temperatures from 323.2 to 403.2 K. The required vapor-liquid-liquid equilibria (VLLE) data were obtained by an experimental procedure based on headspace gas chromatography (HS-GC) developed in the framework of this work. Although all pre-selected ILs have shown good performance, tricyanomethanide-based ILs have been the most promising mass agents.

Nanoporous ceramic supported ionic liquid membranes for CO2 and SO2 removal from flue gas

In this work supported ionic liquid membranes (SILMs) were developed via physical imbibition of 1-alkyl-3-methylimidazolium-based ionic liquids incorporating either the tricyanomethanide ([TCM]−) or the trifluoromethanesulfonate ([TfO]−) anion, into tubular composite ceramic substrates bearing a mesoporous separation layer. The developed SILMs were evaluated with respect to their efficiency for removal of CO2 and SO2 gases from mixtures simulating dry flue gas. In this context, the effect of temperature, feed composition and trans-membrane pressure gradient on CO2/N2 and SO2/CO2 separation performance was studied. For all SILMs, the highest CO2/N2 selectivity values (up to 47.6) were exhibited at ambient temperature unlike to CO2 permeance that was favored by elevation of temperature. The SO2 permeances varied over the range of 3–9.6·10−8molm2s−1Pa−1 being much higher than those determined for CO2 at comparable conditions whereas the permeances of the two gases exhibited opposite temperature dependence. The SO2/CO2 selectivity reached up to 30.7 even though it was markedly reduced with rising temperature and applied pressure gradient, in qualitative accordance to the behavior of CO2/N2 selectivity. Besides physical interaction, the embedded ionic liquid incorporating [TfO]− anions showed also weak chemical interaction with absorbed SO2, the contribution of the which resulted in enhanced SO2 permeation rates as compared to the ones through the embedded tricyanomethanide-based ionic liquids.

Separation of aromatics from n-alkanes using tricyanomethanide-based ionic liquids: Liquid-liquid extraction, vapor-liquid separation, and thermophysical characterization

Ionic liquids (ILs) have been extensively studied as replacements to sulfolane in the separation of aromatics from alkanes. The employment of ILs could reduce energy requirements and operating costs of the aromatic extraction unit as a result of their nonvolatile character. However, the ILs studied so far have shown mass-based aromatic distribution ratios lower than the sulfolane values, which would increase the solvent-to-feed ratio in the extractor. To overcome this drawback, we tested the performance of the 1-butyl-3-methylimidazolium tricyanomethanide ([bmim][TCM]) and the 1-butyl-4-methylpyridinium tricyanomethanide ([4bmpy][TCM]) in the separation of toluene from n-heptane, exhibiting the [4bmpy][TCM] mass-based toluene distribution ratios and toluene/n-heptane selectivities higher than those of sulfolane. We also studied the vapor-liquid recovery of the extracted hydrocarbons from the ILs, obtaining relative volatilities of n-heptane from toluene substantially higher in the presence ILs than those without ILs. A thermophysical characterization of the ILs was also made by measuring their densities, viscosities, thermal stabilities, and estimating their maximum operation temperatures. Finally, the regeneration and reuse of the ILs was studied on successive recovery cycles. After five recovery cycles, ILs have shown the same extractive capacity.

Phase diagrams of binary systems containing tricyanomethanide-based ionic liquids and thiophene or pyridine—New experimental data and PC-SAFT modelling

Isothermal vapor–liquid equilibrium (VLE) phase diagram measurements for the binary systems composed of tricyanomethanide-based ionic liquids and thiophene or pyridine were carried out over the whole range of composition at temperature between (293.15 and 313.15) K using a static apparatus. Moreover, liquid–liquid equilibrium (LLE) phase diagrams for the investigated systems have been determined at atmospheric pressure using a dynamic method. The impact of the cation core structure (imidazolium, or pyridinium, or pyrrolidinium) on the both VLE and LLE has been discussed. Modelling of the investigated properties in terms of molecular-based equation of state, namely perturbed-chain statistical associating fluid theory (PC-SAFT), was performed. Pure-fluid parameters for ionic liquids were obtained from ambient pressure densities and the Hildebrand solubility parameters. Calculations of VLE and LLE employed binary corrections to common combining rules fitted to experimental activity coefficients of thiophene and pyridine reported previously in literature.

Separation of pyridine from heptane with tricyanomethanide-based ionic liquids

Recent approaches employ three tricyanomethanide-based ionic liquids (ILs) as selective solvents of the extraction of pyridine as a model compound of nitrogen compounds in fuels from heptane at T=298.15K and ambient pressure. Experimental data for liquid–liquid phase equilibrium (LLE) were obtained for three ternary systems. The 1-butyl-3-methylimidazolium tricyanomethanide, [BMIM][TCM], 1-butyl-1-methylmorpholinium tricyanomethanide, [BMMOR][TCM] and 1-butyl-1-methylpyridinium tricyanomethanide, [BMPY][TCM] were used due to their immiscibility with gasoline and diesel, negligible vapor pressure, and high selectivity to sulfur- and nitrogen-containing compounds. All of proposed ILs showed similar excellent selectivity with the best Smax=609.3 for and similar high distribution ratio with βmax=9.2 for [BMMOR][TCM] in the extraction of pyridine from heptane and much higher to what is currently published for different ILs. Chromatography analysis showed that IL was not present in the heptane layer. This eliminate the process of the separation of the solvent from the raffinate layer. The data obtained have been correlated with the non-random two liquid NRTL model. The experimental tie-lines and the phase composition in mole fraction in the ternary systems were calculated with an average root mean square deviation (RMSD) of 0.004.

Dynamic Viscosity of Tetracyanoborate- and Tricyanomethanide-Based Ionic Liquids by Dynamic Light Scattering

Low-viscosity ionic liquids (ILs) based on the anions [B(CN)4]− (tetracyanoborate) and [C(CN)3]− (tricyanomethanide) are currently discussed as alternative working fluids for various applications. The dynamic viscosity of such ILs carrying [1-alkyl-MIM]+ (1-alkyl-3-methylimidazolium) cations was investigated via determination of the translational particle diffusion coefficient by dynamic light scattering (DLS). The long-term stability of suspensions of different particles in the ILs, their particle diameters, and the influence of laser power on the measured particle diffusion coefficient for semitransparent ILs were studied. For temperatures from 283 to 353 K at atmospheric pressure, the dynamic viscosity of the four pure ILs forming stable suspensions was obtained with an uncertainty of less than 5% (k = 2) and agrees with literature. Absorption of CO2 at pressures up to 0.87 MPa induced a distinct decrease in the dynamic viscosity. Differences between the viscosities of the different systems can be explained by varying strength of molecular interactions.

Phase behavior of tricyanomethanide-based ionic liquids with alcohols and hydrocarbons

Ionic liquids (ILs) are known as attractive solvents showing high extraction capacity for aromatic hydrocarbons from aliphatic hydrocarbons and for sulfur compounds from alkanes. New experimental results on liquid–liquid phase equilibrium (LLE) in the binary systems of {1-butyl-1-methylpyrrolidinium tricyanomethanide, [BMPYR][TCM]+an alcohol (1-octanol, 1-decanol), or + hydrocarbons (benzene, toluene, ethylbenzene, and heptane)} and of {1-butyl-1-methylmorpholinium tricyanomethanide, [BMMOR][TCM]+an alcohol (1-hexanol, 1-octanol, 1-decanol), or + hydrocarbons (benzene, toluene, ethylbenzene, thiophene, and heptane)} have been determined at atmospheric pressure using a dynamic method. Upper critical solution temperature type of phase behavior for alcohols and a visible tendency for heptane was observed. For aromatic hydrocarbons there is a visible tendency of the lower critical solution temperature phase behavior. Decrease of solubility of alcohol with an increase of its alkyl chain length and of aromatic hydrocarbons with an increase of the alkyl chain length of substituent for all studied systems was detected. The correlation of the experimental data has been carried out using the non-random two liquid (NRTL) equation. The influence of the cation structure on the phase behavior has been discussed. The phase diagrams reported here have been compared to the systems published earlier with the 1-butyl-1-methylpyrrolidinium, or TCM – based ionic liquids.