Carbon Dioxide In Ionic Liquids Research Articles

Transport and Energetics of Carbon Dioxide in Ionic Liquids at Aqueous Interfaces.

A major hurdle in utilizing carbon dioxide (CO2) lies in separating it from industrial flue gas mixtures and finding suitable storage methods that enable its application in various industries. To address this issue, we utilized a combination of molecular dynamics simulations and experiments to investigate the behavior of CO2 in common room-temperature ionic liquids (RTIL) when in contact with aqueous interfaces. Our investigation of RTILs, [EMIM][TFSI] and [OMIM][TFSI], and their interaction with a pure water layer mimics the environment of a previously developed ultrathin enzymatic liquid membrane for CO2 separation. We analyzed diffusion constants and viscosity, which reveals that CO2 molecules exhibit faster mobility within the selected ILs compared to what would be predicted solely based on the viscosity of the liquids using the standard Einstein-Stokes relation. Moreover, we calculated the free energy of translocation for various species across the aqueous-IL interface, including CO2 and HCO3-. Free energy profiles demonstrate that CO2 exhibits a more favorable partitioning behavior in the RTILs compared to that in pure water, while a significant barrier hinders the movement of HCO3- from the aqueous layer. Experimental measurement of the CO2 transport in the RTILs corroborates the model. These findings strongly suggest that hydrophobic RTILs could serve as a promising option for selectively transporting CO2 from aqueous media and concentrating it as a preliminary step toward storage.

Free volume in physical absorption of carbon dioxide in ionic liquids: Molecular dynamics supported modeling

Understanding the mechanisms underlying the carbon dioxide (CO2) absorption in ionic liquids (ILs) is the key to their efficient utilization in industrial flue gas treatment. One of the parameters considered substantially important in the process is the Free Volume. In this study, the Fractional Free Volume (FFV) of 73 ILs was calculated using Molecular Dynamics (MD). A quantitative Structure-Property Relationship (QSPR) study was then employed to predict the FFV, but the validation parameters were unsatisfactory. In the second part, the importance of Free Volume in the absorption of CO2 in ILs was assessed by creating two models to predict Henry’s Law Constant of CO2 in ILs. It was found that the addition of the FFV parameter considerably improved the statistical parameters and predictability of the QSPR model. Furthermore, FFV was found to be heavily dependent on the cation type and its inclusion allowed for the determination of more subtle molecular interactions.

Solubility of carbon dioxide in some imidazolium and pyridinium-based ionic liquids and correlation with NRTL model

In this study, the solubility of carbon dioxide gas in a series of 1-alkyl-4-methyl pyridinium and 1-alkyl-3-methylimidazolium-based ionic liquids with various anions, viz. thiocyanate ([SCN]−), chloride ([Cl]−) and bromide ([Br]−) was investigated using a quartz crystal microbalance at 298.15 K and pressures up to 0.4 MPa. CO2 solubility in the ionic liquids correlates well with the non-random two-liquid (NRTL) model. The results indicate that the cation alkyl chain length and the type of anion have the main effects on the solubility of carbon dioxide in ionic liquids. CO2 solubility in both 1-alkyl-4-methyl pyridinium and 1-alkyl-3-methylimidazolium-based ionic liquids increased with increasing alkyl chain length of the cation. Also, CO2 solubility was strongly dependent on the selection of the anion. CO2 solubility in both 1-alkyl-4-methyl pyridinium and 1-alkyl-3-methylimidazolium-based ionic liquids increased as follows: [SCN]− > [Cl]− > [Br]−.

On the in situ formation of carbenes in ionic liquids

Ionic liquids are considered as tunable designer liquids that may provide the perfect environment or active species for chemical reactions. N-Heterocyclic carbenes are known to be important organocatalysts enabling novel and specific routes for general synthetic strategies. There has been a lot of speculation about the role, stability, and the existence of in situ formed carbenes in ionic liquids. Here, we show that cation stabilised carbenes can exist in room temperature ionic liquids as reactive intermediates detectable with liquid microbeam IR laser desorption mass spectrometry. The experimental results were supported by density functional theory. Intriguingly, we also found that carbenes appear to correlate with and may be the origin of strong chemisorption of carbon dioxide in ionic liquids.

Study of the Parameters Impacting the Photocatalytic Reduction of Carbon Dioxide in Ionic Liquids

AbstractThe front cover artwork is provided by the CP2M laboratory at the University of Lyon (France). The image shows the photocatalytic reduction of CO2 to CO in a bare ionic liquid (IL) medium after an initial CO2 pre‐activation step via the elaboration of an IL–carboxylate complex that bends the CO2. Read the full text of the Article at 10.1002/cptc.202100006.

Study of the Parameters Impacting the Photocatalytic Reduction of Carbon Dioxide in Ionic Liquids

AbstractTo overcome the chemical inertness of CO2, one strategy consists of pre‐activating or destabilizing it, to lower the reduction barrier, by preparing a carbene‐CO2 compound where the CO2 is bent rather than linear. This pre‐activation has been studied in ionic liquids (IL) based on imidazolium as a cation with different anions under conditions of mild pressure, room temperature and UV/Vis light. This screening showed that only 1‐butyl‐3‐methyl‐imidazolium acetate (C1C4ImOAc) was capable of effectively pre‐activating CO2 by chemical sorption to give a more reactive 1‐butyl‐3‐methyl‐imidazolium‐2‐carboxylate (C1C4ImCO2) species. A co‐solvent can be used to consume the photo‐generated holes in Pd/g‐C3N4 as a sacrificial agent but also to provide the protons necessary to reduce CO2. In this study, the influence of several type of co‐solvents such as H2O, isopropanol (iPrOH), and 1‐(2‐hydroxyethyl)‐3‐methyl imidazolium bis(trifluoromethanesulfonyl)imide [C1C2(OH)ImNTf2], has been tested on the activation of CO2 in C1C4ImOAc. We first defined the optimal molar ratio of co‐solvent to be used in order not to compromise CO2 pre‐activation for subsequent application in CO2 transformation. Photocatalytic reductions of CO2 to CO on Pd/g‐C3N4 by varying different parameters demonstrated that CO2 pre‐activation in a mixture of C1C4ImOAc and isopropanol was the most efficient to consider a prospective strategy of CO2 photoreduction in an IL medium.

Absorption characteristic of carbon dioxide in Ionic Liquids based sulfite anion in the pre-combustion condition

Absorption characteristic of carbon dioxide in Ionic Liquids based sulfite anion in the pre-combustion condition

Solubility predictions through LSBoost for supercritical carbon dioxide in ionic liquids

The LSBoost model is developed to predict the solubility of supercritical carbon dioxide in 24 ionic liquids by using critical properties and biphasic system parameters as descriptors. The model is highly accurate and stable.

Rigorous Connectionist Models to Predict Carbon Dioxide Solubility in Various Ionic Liquids

Estimating the solubility of carbon dioxide in ionic liquids, using reliable models, is of paramount importance from both environmental and economic points of view. In this regard, the current research aims at evaluating the performance of two data-driven techniques, namely multilayer perceptron (MLP) and gene expression programming (GEP), for predicting the solubility of carbon dioxide (CO2) in ionic liquids (ILs) as the function of pressure, temperature, and four thermodynamical parameters of the ionic liquid. To develop the above techniques, 744 experimental data points derived from the literature including 13 ILs were used (80% of the points for training and 20% for validation). Two backpropagation-based methods, namely Levenberg–Marquardt (LM) and Bayesian Regularization (BR), were applied to optimize the MLP algorithm. Various statistical and graphical assessments were applied to check the credibility of the developed techniques. The results were then compared with those calculated using Peng–Robinson (PR) or Soave–Redlich–Kwong (SRK) equations of state (EoS). The highest coefficient of determination (R2 = 0.9965) and the lowest root mean square error (RMSE = 0.0116) were recorded for the MLP-LMA model on the full dataset (with a negligible difference to the MLP-BR model). The comparison of results from this model with the vastly applied thermodynamic equation of state models revealed slightly better performance, but the EoS approaches also performed well with R2 from 0.984 up to 0.996. Lastly, the newly established correlation based on the GEP model exhibited very satisfactory results with overall values of R2 = 0.9896 and RMSE = 0.0201.

The Solubility Parameter of Carbon Dioxide and Its Solubility in Ionic Liquids

Carbon dioxide as a solute interacts with solvents mainly via dispersion forces. Its Hildebrand solubility parameter, δH, may therefore be used to predict its dissolution. The usual definition of δH, involving ΔvH, the molar enthalpy of vaporization, is inapplicable for carbon dioxide, it being a gas at the temperatures of technical interest (298 ≤ T/K ≤ 333). The ability of CO2 to accept hydrogen bonds from donor solvents and its appreciable polarizability justify the determination of its Hansen solubility parameters. The definite equation of state of CO2 reported by Span and Wagner permits the determination of the required parameters. The solubility of gaseous carbon dioxide in ionic liquids (room temperature ionic liquids and deep eutectic solvents) has been extensively studied and is discussed in the light of the above statements.

Water and Proton Concentration Affects the Electrocatalytic Conversion of Carbon Dioxide in Ionic Liquids

We report efforts to carry out the reduction of CO2 in mixtures of imidazolium based RTIL in water (H2O) as functions IL:H2O solution ratio and solution pH. IL electrolytes are expensive (relative to water) and many are hydroscopic. Development of CO2 reduction methods based on electrolytes tolerant of significant amounts of water is desirable for large-scale processes. Further, optimization of solution conditions will allow reduced over-potentials, suppression of the competing hydrogen evolution reaction (HER), increases in diffusion rate of dissolved carbon dioxide, and overall improved current efficiencies. In this work we discuss the varying concentration and source of protons in the context of results obtained by carrying out the CO2 reduction in aqueous/IL solutions at various pH values.

Cu-Ni Alloy Catalyzed Electrochemical Carboxylation of Benzyl Bromide with Carbon Dioxide in Ionic Liquid 1-Butyl-3-methylimidazolium tetrafluoroborate

Cu-Ni Alloy Catalyzed Electrochemical Carboxylation of Benzyl Bromide with Carbon Dioxide in Ionic Liquid 1-Butyl-3-methylimidazolium tetrafluoroborate

The effect of cyano groups on the solubility of carbon dioxide in ionic liquids containing cyano groups in anion

The solubility of carbon dioxide (CO2) was investigated using three ionic liquids containing different numbers of cyano groups in the anion, 1-hexyl-3-methylimidazolium tricyanomethanide ([c6mim][C(CN)3]), 1-hexyl-3-methylimidazolium dicyanamide ([c6mim][N(CN)2]), and 1-hexyl-3-methylimidazolium thiocyanate ([c6mim][SCN]). The CO2 solubilities were determined by measuring the bubble point pressures of the CO2+ionic liquid mixtures at temperatures ranging from 303.15 to 373.15 K and pressure up to 105MPa. The experimental results showed that the solubilities of CO2 in ionic liquids increased with pressure, decreased with temperature, and increased with the length of the alkyl chains in the cation. Furthermore, a higher CO2 solubility was achieved in the ionic liquid with more cyano groups in the anion. The experimental data were correlated with the Peng-Robinson equation of state (PR-EoS), using the conventional van der Waals one fluid mixing rule and the modified Lydersen-Joback-Reid method. The average absolute deviation values of pressure (AAD-P) were 0.0658 for CO2+[c6mim][SCN], 0.0633 for CO2+[c6mim][N(CN)2], and 0.0761 for CO2+[c6mim][C(CN)3] system.

Prediction of Gas Solubility in Ionic Liquids Using the Cosmo-Sac Model

Abstract Thermodynamic principles for the dissolution of gases in ionic liquids (ILs) and the COSMO-SAC model are presented. Extensive experimental data of Henry’s law constants for CO2, N2 and O2 in ionic liquids at temperatures of 280-363 K are compared with numerical predictions to evaluate the accuracy of the COSMO-SAC model. It is found that Henry’s law constants for CO2 are predicted with an average relative deviation of 13%. Both numerical predictions and experimental data reveal that the solubility of carbon dioxide in ILs increases with an increase in the molar mass of ionic liquids, and is visibly more affected by the anion than by the cation. The calculations also show that the highest solubilities are obtained for [Tf2N]ˉ. Thus, the model can be regarded as a useful tool for the screening of ILs that offer the most favourable CO2 solubilities. The predictions of the COSMOSAC model for N2 and O2 in ILs differ from the pertinent experimental data. In its present form the COSMO-SAC model is not suitable for the estimation of N2 and O2 solubilities in ionic liquids.

Rigorous modeling of CO2 equilibrium absorption in ionic liquids

Over the past few decades, solution of high amount of carbon dioxide in ionic liquids (ILs) has been the object of extensive studies. It is believed that ILs can be applied to capture CO2 and avoiding greenhouse gas emissions into the atmosphere. In this communication, the predictive capability of the Least Square Support Vector Machine (LSSVM), Adaptive Neuro-Fuzzy Inference System (ANFIS), Multi-Layer Perceptron Artificial Neural Network (MLP-ANN), and Radial Basis Function Artificial Neural Network (RBF-ANN) has been evaluated for estimating carbon dioxide solubility in 67 different ILs as a function of the operational temperature (T), pressure (P) accompanied with the properties of ILs including the critical temperature (Tc), critical pressure (Pc) and, acentric factor (ω). In this regard, an extensive data bank containing 5368 data gathered from the literature was employed. Results obtained from the LSSVM approach indicate its satisfactory predictions than other strategies. Moreover, an outlier analysis was utilized to detect suspected data points. Obtained values of R-squared (R2), Mean Squared Error (MSE) were 0.9942 & 0.00035, 0.9135 & 0.004883, 0.9135 & 0.004883, and 0.9135 & 0.004883 for the LSSVM, ANFIS, MLP-ANN, and RBF-ANN respectively. Accordingly, the LSSVM strategy was introduced as a great tool for estimating CO2 solubility in such ionic liquids, which is easy to apply and can avoid time-consuming experimental measurement and expensive experimental apparatuses as well as complicated interpretation procedures. In addition, it can help chemists and chemical engineers to have a low parameter model with satisfactory results for the estimation of CO2 solubility in ILs.

Influence of Fluorination on the Solubilities of Carbon Dioxide, Ethane, and Nitrogen in 1-n-Fluoro-alkyl-3-methylimidazolium Bis(n-fluoroalkylsulfonyl)amide Ionic Liquids.

The effect on gas solubilities of adding partially fluorinated alkyl side chains either on imidazolium-based cations or on bis(perfluoroalkylsulfonyl)amide anions was studied. The aim was to gain knowledge of the mechanisms of dissolution of gases in fluorinated ionic liquids and, if possible, to improve physical absorption of carbon dioxide in ionic liquids. We have determined experimentally, in the temperature range of 298-343 K and at pressures close to atmospheric pressure, the solubility and thermodynamics of solvation of carbon dioxide, ethane, and nitrogen in the ionic liquids 1-octyl-3-methylimidazolium bis[trifluoromethylsulfonyl]amide ([C8mim][NTf2]), 1-octyl-3-methylimidazolium bis[pentafluoroethylsulfonyl]amide ([C8mim][BETI]), 1-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)-3-methylimidazolium bis[trifluoromethylsulfonyl]amide ([C8H4F13mim][NTf2]), and 1-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)-3-methylimidazolium bis[pentafluoroethylsulfonyl]amide ([C8H4F13mim][BETI]). Ionic liquids with partial fluorination on the cation were found to exhibit higher carbon dioxide and nitrogen mole fraction solubilities but lower ethane solubilities, compared to those of their hydrogenated counterparts. Molecular simulation provided insights about the mechanisms of solvation of the different gases in the ionic liquids.

Rotational dynamics of carbon dioxide in ionic liquids

The rotational dynamics of carbon dioxide (CO2) in four ionic liquids (ILs) has been investigated by 17O NMR T1 measurement. The ILs have the bis(trifluoromethanesulfonyl)imide anion ([NTf2]−) in common while they have diversity in the cationic component. The cations studied are 1-ethyl-3-methylimidazolium ([C2C1im]+), 1-butyl-3-methylimidazolium ([C4C1im]+), tributylmethylphosphonium ([P4441]+) and tetraoctylphosphonium ([P8888]+) cations. The observed rotational relaxation times (τ2R) are smaller than the prediction by the Stokes-Einstein-Debye (SED) theory (subslip behavior). When correction is made to the SED theory with respect to the solvent/solute molecular size ratio according to Gierer and Wirtz (Z. Naturforschg 1953, 8a, 832), a reasonable agreement between theory and experiment is reached for the τ of CO2 in [C2C1im][NTf2] and [C4C1im][NTf2]. The modified theory, however, still overestimates the τ in [P4441][NTf2] and [P8888][NTf2]. These results demonstrate that the hydrodynamic model does not work well for the extreme end of the solvent/solute size ratio.

Volumetric and phase behaviour of mixtures of fluoroalkylphosphate-based ionic liquids with high pressure carbon dioxide

The high-pressure solubility of carbon dioxide in ionic liquids based on tris(pentafluoroethyl)trifluorophosphate ([eFAP]) anion, combined with 1-ethyl-3-methylimidazolium ([emim]), 1-butyl-3-methylimidazolium ([bmim]) and 1-hexyl-3-methylimidazolium ([hmim]) cation, was determined experimentally at the temperature of 313.15K and pressures up to 10MPa. Measurements of the volume expansion of the liquid phase upon carbon dioxide dissolution are also reported. The obtained results show that the solubility of CO2 in ionic liquids with the fluoroalkylphosphate anion, as well as the CO2-induced volume expansion of the liquid, are among the highest so far reported for ionic liquids where CO2 dissolves through “physical” mechanisms.

Volumetric and phase behaviour of mixtures of tetracyanoborate-based ionic liquids with high pressure carbon dioxide

The high-pressure solubility of carbon dioxide in ionic liquids based on tetracyanoborate anion, 1-ethyl-3-methylimidazolium tetracyanoborate ([emim][B(CN)4]) and 1-hexyl-3-methylimidazolium tetracyanoborate ([hmim][B(CN)4]), was determined experimentally at the temperature of 313.15K and pressures up to 19MPa. Additionally, measurements of volume expansion of a liquid phase, based on a change in total or molar volume of a liquid upon carbon dioxide addition, are reported. The obtained results show that CO2 has a high solubility in tetracyanoborate-based ionic liquids, comparable, or even slightly higher, to the CO2 solubility in fluorinated CO2-philic ionic liquids. Approximately 60% CO2-induced volume expansion of the liquid was observed at the highest pressures, an unprecedented result for ionic liquid+ CO2 systems.

Prediction carbon dioxide solubility in presence of various ionic liquids using computational intelligence approaches

Ionic liquids (ILs) are highly promising for industrial applications such as design and development of gas sweetening processes. For a safe and economical design, prediction of carbon dioxide solubility by a trustworthy model is really essential. In this research, based on the pressure and temperature of system and the critical properties such as critical temperature (Tc) and critical pressure (Pc) and also acentric factor (ω) and molecular weight (Mw) of pure ionic liquids, a multi-layer perceptron artificial neural network (MLP-ANN) and an adaptive neuro-fuzzy interference system (ANFIS) have been developed to estimate carbon dioxide solubility in presence of various ILs over wide ranges of pressure, temperature and concentration. To this end, 728 experimental data points collected from the literature have been used for implementation of these models. To verify the proposed models, regression analysis has been conducted on the experimental and predicted solubility of carbon dioxide in ILs. Moreover, in this study, a comparison between experimental carbon dioxide solubilities and predicted values of carbon dioxide solubility by thermodynamic models based on Peng–Robinson (PR) and Soave–Redlich–Kwong (SRK) equation of states has been performed. For MLP-ANN, coefficient of determination (R2) between experimental and predicted values is 0.9972 and mean squared errors (MSEs) is 0.000133 and the values of R2=0.9336 and MSE=0.002942 were obtained for ANFIS model while, the values of R2 and MSE for PR-EOS were 0.7323 and 0.002702 respectively, and also, R2=0.6989 and MSE=0.005578 were obtained for SRK-EOS model. Therefore, in current study, ability and better performance of MLP-ANN as an accurate correlation for estimating carbon dioxide solubility in ILs was showed against other alternative models.