Conductor-like Screening Model For Real Solvents Model Research Articles

Evaluation of amine-based ionic liquids as potential solvents for hydrogen sulfide absorption using COSMO-RS: Computational and experimental validation

Ionic liquids (ILs) is an effective way to convert and remove hydrogen sulfide, H2S from natural gas streams. Amine-based ILs have recently been discovered due to their efficiency of removing H2S due to their excellent characteristics. However, the selection of potential amine-based ILs from a wide range combination of cations and amine-based anions are rather challenging if performed experimentally. Conductor-like Screening Model for Real Solvents (COSMO-RS) was used for the prediction of liquids thermodynamics such as activity coefficient at infinite dilution, selectivity, capacity and performance index (PI) values to evaluate the performance of each amine-based ILs and determine the most efficient ILs for H2S absorption without requiring any experimental data. A total of 42 previously unexplored ionic liquids, amine-based ILs from a combination of 7 amine cations and 6 anions were screened by COSMO-RS model. The findings from COSMO-RS prediction results revealed that ILs without aromatic rings displayed higher efficiencies compared to ILs with aromatic rings. Moreover, N,N,N′,N′-tetramethyl-1,3-propanediamine chloride, [TMPDA][Cl] cation-anion combinations displayed the highest PI value of 52.55 among the screened ILs thus, predicted as the most efficient ILs for H2S absorption. The experimental results obtained validated the COSMO-RS predictions with an approximation of ± 4.51% discrepancies between predicted and experimental data. Hence, it is concluded that COSMO-RS can be used for a reliable pre-experimental prediction and amine-based ILs approach has a huge potential for effective H2S absorption in industrial applications.

Screening of Suitable Ionic Liquids as Green Solvents for Extraction of Eicosapentaenoic Acid (EPA) from Microalgae Biomass Using COSMO-RS Model.

Omega-3 poly unsaturated fatty acids (PUFA) particularly eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), have many health benefits including reducing the risk of cancer and cardiovascular disease. Recently, the use of ionic liquids (ILs) in lipid extraction from microalgae provides the potential to overcome common drawbacks, offers several other benefits. To date, very limited researches are available to focus on extracting microalgae lipid and PUFA in particular by using ILs. The objective of current work is to screen the potential ILs that can be applied in EPA extraction. In this study, fast ILs screening was performed with the help of a conductor like screening model for real solvents (COSMO-RS) and the ILs with higher capacity values for use in extraction of EPA were compared. According to the results, the highest capacity for EPA extraction among 352 screened cation/anion combinations belongs to [TMAm][SO4]. It is expected to achieve a higher yield of EPA once applying this combination as the solvent in the process of extraction. ILs with small anions were observed to have higher capacities, as well possessing higher charge density compared to larger ones, and therefore, they are more preferable for extraction purposes. Moreover, shorter alkyl chain cations are preferred when using imidazolium-based IL, which agrees with experimental data.

Ionic liquids for the separation of benzene and cyclohexane – COSMO-RS screening and experimental validation

The separation of benzene and cyclohexane from their mixture is difficult to perform via conventional distillation because of their close boiling points. In this work, liquid-liquid extraction using ionic liquids (ILs) is suggested for this purpose and 16 cations and 13 anions were selected to form 208 possible ILs screened with the Conductor-like Screening Model for Real Solvents (COSMO-RS) module. The screening result was experimentally validated by liquid–liquid extraction using four of the top ranked ILs, namely 1-ethyl-3-methylimidazolium acetate ([C2mim][Ac]), 1-ethyl-3-methylimidazolium dicyanamide ([C2mim][N(CN)2]), 1-ethyl-3-methylimidazolium thiocyanate ([C2mim][SCN]) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][Tf2N]). The ternary liquid–liquid equilibria for these ILs with benzene and cyclohexane were investigated at 25 °C and 1 atm with feed concentration of benzene ranging from 10 to 60 wt%. Good agreement was achieved between the tie-lines obtained from the COSMO-RS model and those obtained experimentally. The performance of ILs used in this study was compared with organic solvents, other ILs, and deep eutectic solvents reported in literature. The results of selectivity and distribution ratio confirmed that COSMO-RS was a reliable method for solvent screening and demonstrated the suitability of the selected ILs as extracting solvents. In all ternary systems, no IL was detected in the cyclohexane layer and the concentration of cyclohexane in the IL layer was very low. This observation indicated that there was minimum cross-contamination between the phases and therefore less energy will be required for the solvent recovery.

Quantum chemical insights and continuum solvation predictions on the dissolution of bituminous and anthracite coal in Ionic Liquid

The current work reports the ab initio calculations on Ionic Liquids (ILs) with bituminous and anthracite coal particles using both Density Functional Theory (DFT) and solvation predictions using COnductor like Screening MOdel for Real Solvents (COSMO-RS) model. The commercial cations used in the study were 1-butyl-1-methylpyrrolidinium ([BMPYR]), 1-methyl-3-propylimmidazolium ([MPIM]), Tributylmethylammonium ([TMA]) and Tributylmethylphosphonium ([MTBP]). The corresponding anions were methyl carbonate ([CH3CO3]), dicyanamide ([N(CN)2]), bis(trifluromethylesulfonyle)imide ([Tf2N]) and methylsulfate ([MeSO4]). A three-tier approach comprising of HOMO-LUMO energies, quantum descriptors (electronegativity, electrophilicity, global hardness, global softness); and Infinite Dilution Activity Coefficient (IDAC) by COSMO-RS model were chosen for studying the simultaneous interaction. 1-butyl-1-methylpyrrolidinium methylcarbonate [BMPYR][CH3CO3] and 1-methyl-3-propylimmidazolium methylcarbonate [MPIM][CH3CO3] were the recommended IL's on the basis of HOMO-LUMO band energy gap. A similar trend for IL-coal interactions were followed up and confirmed by the quantum descriptors and IDAC predictions. A direct correspondence between reported swelling ration and excess Gibb's energy has also been attempted.

Vapor Pressure Measurements for Binary Mixtures Containing Ionic Liquid and Predictions by the Conductor-like Screening Model for Real Solvents

The vapor pressures for binary systems containing the ionic liquid (IL) 1-ethyl-3-methylimidazoliun tetrafluoroborate ([EMIM][BF4]) and a solute were measured with a modified equilibrium still, and the solutes investigated were benzene, toluene, thiophene, and water. The results indicate that the IL [EMIM][BF4] produces an obvious effect on the vapor pressures of binary systems, and the vapor pressures increase with the temperature. The vapor pressures of binary mixtures (i.e., [EMIM][BF4] + benzene, [EMIM][BF4] + thiophene, and [EMIM][BF4] + toluene) first increase with the increase of mole fraction of the solute, and then almost keep stable. However, the vapor pressures of the mixture of water and [EMIM][BF4] increase linearly with the increase of mole fraction of water. The vapor pressure experimental data for the binary systems were compared with the predicted values by the conductor-like screening model for real solvents (COSMO-RS) model. The results demonstrate that the COSMO-RS model gives quantita...

Steric and energetic interpretations of the equilibrium adsorption of two new pyridinium ionic liquids and ibuprofen on a microporous activated carbon cloth: Statistical and COSMO-RS models

The adsorption isotherms of two new ionic liquids (4-tert-butyl-1-propylpyridinium bromide: IL1 and (4-ter-butyl-1-(2 carboxyethyl) pyridinium bromide: IL2) and ibuprofen (2-[4-(2-methylpropyl) phenyl] propanoic acid: IBP) on an activated carbon cloth were studied at 286, 298 and 313 K. Experimental adsorption isotherms were simulated by a single energy monolayer model using statistical physics, allowing to determine the number of molecules per site (n), the density of receptor sites (NM) and the concentration at half saturation (c1/2). Simulation results suggested that two adsorbates were docked per receptor sites of the activated carbon cloth surface. As a function of temperature, the study of the monolayer adsorbed quantity has indicated that the adsorption process is exothermic. The magnitudes of the estimated adsorption energies have indicated that IBP and ILs have been physisorbed on the adsorbent. The conductor-like screening model for real solvents (COSMO-RS) was applied to calculate three specific interaction energies of ILs and IBP with a graphene layer, i.e., the electrostatic misfit energy (EMF), the hydrogen-bonding energy (EHB) and the Van der Waals energy (EvdW). The COSMO-RS model has proved that the interaction of all the three studied adsorbates with a graphene layer mainly depends on the Van der Waals contribution. The highest interaction energies of IL2 and IBP with the carbon surface have been explained by the additional contribution of hydrogen bond attributed to the presence of a carboxyl group on these molecules.

Prediction of ionic liquids phase equilibrium with the COSMO-RS model

Unlimited number of permutations with respect to cation and anion combinations of ionic liquids as well as large number of existed azeotropic mixtures cause experimentally impossibility to screen all of possible systems of these compounds. Therefore, predictive models have been developed as COnductor-like Screening MOdel for Real Solvents (COSMO-RS) – an a priori predictive method independent of experimental data, which only requires the information is the molecular structure of the compounds.In this work, COSMO-RS model has been used in prediction of activity coefficients at infinite dilution of about 60 different organic solutes and water in 12 ionic liquids as well as ternary liquid–liquid equilibrium in 13 systems: (ionic liquid + methanol + heptane), (ionic liquid + thiophene + heptane) and (ionic liquid + benzothiophene + heptane). The model predictions are compared with experimental data (obtained in previously in our laboratory) in order to evaluate the accuracy of COSMO-RS model in phase equilibrium prediction of this kind of systems.

Comprehensive study on the impact of the cation alkyl side chain length on the solubility of water in ionic liquids

A comprehensive study on the phase behaviour of two sets of ionic liquids (ILs) and their interactions with water is here presented through combining experimental and theoretical approaches. The impact of the alkyl side chain length and the cation symmetry on the water solubility in the asymmetric [CN−1C1im][NTf2] and symmetric [CN−1CN−1im][NTf2] series of ILs (N up to 22), from 288.15K to 318.15K and at atmospheric pressure, was studied. The experimental data reveal that the solubility of water in ILs with an asymmetric cation is higher than in those with the symmetric isomer. Several trend shifts on the water solubility as a function of the alkyl side chain length were identified, namely at [C6C1im][NTf2] for asymmetric ILs and at [C4C4im][NTf2] and [C7C7im][NTf2] for the symmetric ILs. To complement the experimental data and to further investigate the molecular-level mechanisms behind the dissolution process, density functional theory calculations, using the Conductor-like Screening Model for Real Solvents (COSMO-RS) and the electrostatic potential-derived CHelpG, were performed. The COSMO-RS model is able to qualitatively predict water solubility as a function of temperature and alkyl chain lengths of both symmetric and asymmetric cations. Furthermore, the model is also capable to predict the somewhat higher water solubility in the asymmetric cation, as well as the trend shift as a function of alkyl chain lengths experimentally observed. Both COSMO-RS and the electrostatic potential-derived CHelpG show that the interactions of water and the IL cation take place on the IL polar region, namely on the aromatic head and adjacent methylene groups that explains the differences in water solubility observed for cations with different chain lengths. Furthermore, the CHelpG calculations for the isolated cations in the gas phase indicates that the trend shift of water solubility as a function of alkyl chain lengths and the difference of water solubility in symmetric may also result from the partial positive charge distribution/contribution of the cation.

The effect of the cation alkyl chain branching on mutual solubilities with water and toxicities.

The design of ionic liquids has been focused on the cation-anion combinations but other more subtle approaches can be used. In this work the effect of the branching of the cation alkyl chain on the design of ionic liquids (ILs) is evaluated. The mutual solubilities with water and toxicities of a series of bis(trifluoromethylsulfonyl)-based ILs, combined with imidazolium, pyridinium, pyrrolidinium, and piperidinium cations with linear or branched alkyl chains, are reported. The mutual solubility measurements were carried out in the temperature range from (288.15 to 323.15) K. From the obtained experimental data, the thermodynamic properties of the solution (in the water-rich phase) were determined and discussed. The COnductor like Screening MOdel for Real Solvents (COSMO-RS) was used to predict the liquid-liquid equilibrium. Furthermore, molecular dynamic simulations were also carried out aiming to get a deeper understanding of these fluids at the molecular level. The results show that the increase in the number of atoms at the cation ring (from five to six) leads to a decrease in the mutual solubilities with water while increasing their toxicity, and as expected from the well-established relationship between toxicities and hydrophobicities of ILs. The branching of the alkyl chain was observed to decrease the water solubility in ILs, while increasing the ILs solubility in water. The inability of COSMO-RS to correctly predict the effect of branching alkyl chains toward water solubility on them was confirmed using molecular dynamic simulations to be due to the formation of nano-segregated structures of the ILs that are not taken into account by the COSMO-RS model. In addition, the impact of branched alkyl chains on the toxicity is shown to be not trivial and to depend on the aromatic nature of the ILs.

COSMO-RS modeling on the extraction of stimulant drugs from urine sample by the double actions of supercritical carbon dioxide and ionic liquid

This work presents the first research linking chemical engineering and sport science as far as we know. The COSMO-RS (conductor-like screening model for real solvents) model was used to make a priori prediction for the extraction of stimulants from aqueous solution by the double action of supercritical carbon dioxide (SC CO 2 ) and ionic liquid. It was found that the suitable ionic liquids should have small molecular volume, unbranched group and no sterical shielding effect around anion charge center, and thus [ C 2 MIM ] + [ OAc ] - is the best among all the ionic liquids investigated. The calculated results from the COSMO-RS model were qualitatively consistent with those from experiments. On this basis, partition coefficients of amphetamine (C9N) and nikethamide (C10N) between aqueous phase and supercritical fluid (or MTBE) phase at different temperatures were calculated. It was shown that the separation efficiency of supercritical extraction with ionic liquid is generally higher than that of traditional liquid–liquid extraction. The modeling present can also be extended to the separation of trace amount of organic substances from aqueous solutions for other purposes.

Selection of entrainers in the 1-hexene/ n-hexane system with a limited solubility

Vapor-liquid equilibria (VLE) have been measured for five 1-hexene/ n-hexane/ionic liquid systems and 1-hexene/ n-hexane/NMP ( N-methyl-2-pyrrolidone) system with a headspace-gas chromatography (HSGC) apparatus at 333.15 K. The ionic liquids investigated were 1,3-dimethylimidazolium tetrafluoroborate [C 2MIM] +[BF 4] −, 1-butyl-3-methylimidazolium tetrafluoroborate [C 4MIM] +[BF 4] −, 1-methyl-3-octylimidazolium tetrafluoroborate [C 8MIM] +[BF 4] −, 1,3-dimethylimidazolium dicyanamide [C 2MIM] +[N(CN) 2] − and 1-octylquinolinium bis(trifluoromethylsulfonyl)amide [C 8Chin] +[BTA] −. It was found that at low feeding concentration of 1-hexene and n-hexane, the separation ability of ionic liquids is in the order of [C 2MIM] +[BF 4] − > [C 4MIM] +[BF 4] − ≈ [C 2MIM] +[N(CN) 2] − > [C 8MIM] +[BF 4] − > [C 8Chin] +[BTA] −, which is consistent with the priori prediction of the COSMO-RS (conductor-like screening model for real solvents) model. But at high feeding concentration, the separation ability of ionic liquids is in the order of [C 2MIM] +[BF 4] − < [C 4MIM] +[BF 4] − ≈ [C 2MIM] +[N(CN) 2] − < [C 8MIM] +[BF 4] − < [C 8Chin] +[BTA] −. The liquid demixing effect should be taken into account. The activity coefficients of 1-hexene and n-hexane at infinite dilution calculated with the COSMO-RS model were correlated using the NRTL, Wilson and UNIQUAC model. In this work the predictive results from the COSMO-RS model and UNIFAC model for the 1-hexene/ n-hexane and 1-hexene/ n-hexane/NMP systems were compared. The UNIFAC model is one of the most important academic contributions by Prof. Jürgen Gmehling.