Conductor-like Screening Model For Real Solvents Research Articles

Desulfurization of fuel oils: Mutual solubility of ionic liquids and fuel oil

Extractive and oxidative desulfurization of fuel oil using ionic liquids (ILs) as solvents have been intensively studied recently. In such processes, the mutual solubility of ILs and fuel oil is still a major concern. Less mutual solubility is desired to reduce the loss of ILs and the contamination of fuel oil. To screen the ideal ILs with less mutual solubility with fuel oil and to understand the effects of ILs structural characteristics on the mutual solubility, we employed Conductor-like Screening Model for Real Solvents (COSMO-RS) to calculate the mutual solubility of 1830 ILs and model fuel oil. The influences of ILs structural characteristics such as cationic nature, cationic alkyl chain length, cationic symmetry, anionic nature, anionic alkyl chain length and functional group on the mutual solubility are investigated from micro-level view with σ-profile, σ-moment and COSMO-RS energies. The mutual solubility is strongly dependent on cation or anion species and is highly influenced by van der Waals (vdW) and hydrogen-bonding (HB) energies. Cations with smaller non-polarity, shorter alkyl chain length and less symmetry tend to have weaker vdW energies and smaller mutual solubility, while anions with larger polarity tend to have stronger HB energies and smaller mutual solubility. The functional groups also show remarkable effects on mutual solubility; those functional groups that decrease the non-polarity and vdW energies or increase the polarity and HB energies favor the small mutual solubility. Moreover, experimental determinations of the mutual solubility indicate [C1pyr]H2PO4 is a good solvent for desulfurization. This work provides the theoretical basis to design and select the ILs, which have small mutual solubility with fuel oil.

Complexation and molecular modeling studies of europium(III)–gallic acid–amino acid complexes

With many metal-based drugs extensively used today in the treatment of cancer, attention has focused on the development of new coordination compounds with antitumor activity with europium(III) complexes recently introduced as novel anticancer drugs. The aim of this work is to design new Eu(III) complexes with gallic acid, an antioxida'nt phenolic compound. Gallic acid was chosen because it shows anticancer activity without harming health cells. As antioxidant, it helps to protect human cells against oxidative damage that implicated in DNA damage, cancer, and accelerated cell aging. In this work, the formation of binary and ternary complexes of Eu(III) with gallic acid, primary ligand, and amino acids alanine, leucine, isoleucine, and tryptophan was studied by glass electrode potentiometry in aqueous solution containing 0.1M NaNO3 at (298.2±0.1) K. Their overall stability constants were evaluated and the concentration distributions of the complex species in solution were calculated. The protonation constants of gallic acid and amino acids were also determined at our experimental conditions and compared with those predicted by using conductor-like screening model for realistic solvation (COSMO-RS) model. The geometries of Eu(III)–gallic acid complexes were characterized by the density functional theory (DFT). The spectroscopic UV–visible and photoluminescence measurements are carried out to confirm the formation of Eu(III)–gallic acid complexes in aqueous solutions.

Overview of Activity Coefficient of Thiophene at Infinite Dilution in Ionic Liquids and their Modeling Using COSMO-RS

Ionic liquids (ILs) gained a lot of attention, from both academe and industry, as alternative liquids for different types of applications. Chemical and physical characteristics can be designed with the large availability of cation and anions. Experimental measurement of all these systems is not practically feasible, hence requiring the use of a computational predictive model study. This work evaluates the prediction of the activity coefficient (γs∞) at infinite dilution in several classes of ILs using the conductor-like screening model for real solvents (COSMO-RS), a model based on unimolecular quantum chemistry calculations. Comparison of the experimental γs∞ value with COSMO-RS predicted data is carried out, and absolute average relative deviation was determined to be 24.1%, indicating that the COSMO-RS model presents a reliable prediction to determine γs∞ in a wide range of ILs. The observation also confirms that polarizability of ILs plays a crucial role in their interaction with thiophene. With respe...

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.

Application of COSMO-RS in Investigating Ionic Liquid as Thermodynamic Hydrate Inhibitor for Methane Hydrate

Gas hydrate formation in oil and gas pipelines has resulted in flow assurance issues. To mitigate hydrate formation, recently, ionic liquid (IL) inhibitors have been studied frequently using experimental method. However, experimental testing alone is insufficient to examine all potential ionic liquid combinations due to large amounts of cation and anion. Therefore, in this work, the thermodynamic inhibition ability of ILs have been predicted based on its fundamental property, or specifically hydrogen bonding energy. For this, Conductor-Like Screening Model for Real Solvent (COSMO-RS) software is used to simulate and study the fundamental property of IL-hydrate system. Relationship between IL inhibition ability and hydrogen bonding energy is then justified. The pattern of relationship is next applied to rank the IL inhibition ability. Through this method, pre-screening of ineffective ILs can be conducted and hence narrows down the scope of ILs waiting to be tested experimentally. As consequence, effective thermodynamic hydrate inhibitor could be discovered faster and be applied in industry.

Aqueous biphasic systems composed of ionic liquids and polypropylene glycol: insights into their liquid-liquid demixing mechanisms.

Novel ternary phase diagrams of aqueous biphasic systems (ABSs) composed of polypropylene glycol with an average molecular weight of 400 g mol(-1) (PPG-400) and a vast number of ionic liquids (ILs) were determined. The large array of selected ILs allowed us to evaluate their tuneable structural features, namely the effect of the anion nature, cation core and cation alkyl side chain length on the phase behaviour. Additional evidence on the molecular-level mechanisms which rule the phase splitting was obtained by (1)H NMR (Nuclear Magnetic Resonance) spectroscopy and by COSMO-RS (Conductor-like Screening Model for Real Solvents). Some systems, for which the IL-PPG-400 pairs are completely miscible, revealed to be of type "0". All data collected suggest that the formation of PPG-IL-based ABSs is controlled by the interactions established between the IL and PPG, contrarily to previous reports where a "salting-out" phenomenon exerted by the IL over the polymer in aqueous media was proposed as the dominant effect in ABS formation. The influence of temperature on the liquid-liquid demixing was also evaluated. In general, an increase in temperature favours the formation of an ABS in agreement with the lower critical solution temperature (LCST) phase behaviour usually observed in polymer-IL binary mixtures. Partition results of a dye (chloroanilic acid, in its neutral form) further confirm the possibility of tailoring the phases' polarities of IL-PPG-based ABSs.

Binary adsorption isotherms of two ionic liquids and ibuprofen on an activated carbon cloth: simulation and interpretations using statistical and COSMO-RS models

Chemical structures of IL1, IL2 and IBP.

Phase Equilibria upon Denitrification of Liquid Fuels Using Imidazolium-Based Ionic Liquids: Experiment and Quantum Chemical Calculations

The interaction between pyrrole and pyridine with 1-ethyl-3-methylimidazolium ethyl sulfate ([EMIM][EtSO4]) was investigated using quantum chemical calculations, the conductor-like screening model for real solvent (COSMO-RS) approach, and experimental ternary liquid–liquid equilibrium (LLE) data. Geometry optimization was performed usign density functional theory (DFT) with B3LYP functional and 6-311+G* basis set for individual species and complexes of [EMIM][EtSO4] with pyrrole/pyridine. The amount of charge transfer in [EMIM][EtSO4] + pyrrole was found to be ∼20% greater than that in [EMIM][EtSO4] + pyridine, indicating that CH−π interaction was stronger with pyrrole. The more negative interaction energy for the complex [EMIM][EtSO4] + pyrrole implies that [EMIM][EtSO4] has a more favorable interaction with pyrrole than with pyridine. σ-profile analysis using COSMO-RS confirmed the pivotal role of the CH-π interaction between [EMIM][EtSO4] and pyrrole or pyridine. Ternary LLE experiments were performed ...

Surface tensions of ionic liquids: Non-regular trend along the number of cyano groups

Ionic liquids (ILs) with cyano-functionalized anions are a set of fluids that are still poorly characterized despite their remarkably low viscosities and potential applications. Aiming at providing a comprehensive study on the influence of the number of –CN groups through the surface tension and surface organization of ILs, the surface tensions of imidazolium-based ILs with cyano-functionalized anions were determined at atmospheric pressure and in the (298.15–343.15) K temperature range. The ILs investigated are based on 1-alkyl-3-methylimidazolium cations (alkyl = ethyl, butyl and hexyl) combined with the [SCN]-, [N(CN)2]−, [C(CN)3]− and [B(CN)4]− anions. Although the well-known trend regarding the surface tension decrease with the increase of the size of the aliphatic moiety at the cation was observed, the order obtained for the anions is more intricate. For a common cation and at a given temperature, the surface tension decreases according to: [N(CN)2]− > [SCN]− > [C(CN)3]− > [B(CN)4]-. Therefore, the surface tension of this homologous series does not decrease with the increase of the number of –CN groups at the anion as has been previously shown by studies performed with a more limited matrix of ILs. A maximum in the surface tension and critical temperature was observed for [N(CN)2]-based ILs. Furthermore, a minimum in the surface entropy, indicative of a highly structured surface, was found for the same class of ILs. All these evidences seem to be a result of stronger hydrogen-bonding interactions occurring in [N(CN)2]-based ILs, when compared with the remaining CN-based counterparts, and as sustained by cation-anion interaction energies derived from the Conductor Like Screening Model for Real Solvents (COSMO-RS).

COSMO-RS and solvatochromic parameters to investigate the correlation between P3HT assembly and the nucleophilicity of solvents

The use of specific binary solvent mixtures to drive the self-assembly of semiconducting polymers, such as poly(3-hexylthiophene) (P3HT), as a route to well-organized films and optoelectronic composites has garnered a lot of interest. To date, the dominant intermolecular forces in these mixtures have only been partially scrutinized. The σ-profiles obtained from the Conductor-like Screening Model for Real Solvents (COSMO-RS) calculations are used to assess the lipophilic, electrophilic, and nucleophilic characteristics of 48 binary solvent mixtures. Correlations between these characteristics and experimentally measured Kamlet–Taft (α, β, π*) and ETN solvatochromic parameters are examined to assess the nature of the solvent-polymer interactions directing the assembly of P3HT into macromolecular architectures. The experimental and computed σ-profiles results are in good agreement and indicate that while the polarity of the solvent impacts the general solubility behavior of P3HT, the nucleophilicity of the solvent mixture is a key factor in dictating the structural order of P3HT aggregates.

Separation of Aeruginosin-865 from Cultivated Soil Cyanobacterium (Nostoc sp.) by Centrifugal Partition Chromatography combined with Gel Permeation Chromatography

Aeruginosin-865 was isolated from cultivated soil cyanobacteria using a combination of centrifugal partition chromatography (CPC) and gel permeation chromatography. The solubility of Aer-865 in different solvents was evaluated using the conductor-like screening model for real solvents (COSMO-RS). The CPC separation was performed in descending mode with a biphasic solvent system composed of water-n-BuOH-acetic acid (5:4:1, v/v/v). The upper phase was used as a stationary phase, whereas the lower phase was employed as a mobile phase at a flow rate of 10 mL/min. The revolution speed and temperature of the separation column were 1700 rpm and 25 degrees C, respectively. Preparative CPC separation followed by gel permeation chromatography was performed on 50 mg of crude extract yielding Aer-865 (3.5 mg), with a purity over 95% as determined by HPLC. The chemical identity of the isolated compound was confirmed by comparing its spectroscopic data (UV, HRESI-MS, HRESI-MS/MS) with those of an authentic standard and data available in the literature.

Tuning ionic liquids for natural gas dehydration using COSMO-RS methodology

The quantum chemical COSMO-RS (Conductor like Screening Model for Real Solvents) methodology was applied to evaluate the ability ionic liquids as alternative solvents for dehydration of natural gas. First, a general evaluation of COSMO-RS model to predict activity coefficients at infinite dilution of water in ionic liquids were performed by comparing the computed results with a set of experimentally measured activity coefficient of water in different ionic liquids over various temperatures. The mean prediction error (MPE) and linear correlation coefficient (R2) between the experimental and predicted activity coefficients are 29.9% and 0.968, respectively. Then, a detailed analysis of water and ionic liquids behaviors and the effects of possible structural variation of ionic liquids on the water-ionic liquids interactions were performed using the sigma-profile and sigma-potential generated by COSAMO-RS model. For which, a total of 31 cations and 43 anions resulting in 1333 possible combinations were screened via COSMO-RS model by calculating the activity coefficient of water in these ionic liquids at infinite dilution over temperature range of (298.15–368.15) K. It was found that ionic liquids the contain cations with longer alkyl chain show less affinity for water molecules. Moreover, ionic liquids with fluorinated and cyano anions shows lower affinity and selectivity for water molecules. However, ionic liquids containing carboxylate and amino acid based anions and cations with shorter alkyl side chain have strong affinity and more selectivity for water molecules.

Desulfurization of Fuel Oil: Conductor-like Screening Model for Real Solvents Study on Capacity of Ionic Liquids for Thiophene and Dibenzothiophene

To screen and use ionic liquids (ILs) as environmental-friendly extractive solvents in removing aromatic sulfur compounds (S-compounds) from fuel oils, the knowledge of their capacity for S-compounds (or solubility of S-compounds in ILs) is very important. In this work, the capacities of 1860 potential ILs (30 anions, 62 cations) for two representative S-compounds of thiophene (TS) and dibenzothiophene (DBT) are calculated using conductor-like screening model for real solvents (COSMO-RS). The influences of cation family, cation alkyl chain length, cation symmetry, anion nature, anion alkyl chain length, and functional group on the capacity are extensively discussed and are understood from microlevel view with σ-profile, σ-moments, and COSMO-RS energies. It is observed that the capacity is very dependent on cation and anion structure characteristics and is in a very wide range (e.g., 10–3∼101 for TS, 10–3∼102 for DBT); the van der Waals (vdW) and hydrogen-bonding (HB) energies have significant effects on t...

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.

High-pressure phase equilibrium in the {carbon dioxide (1) + 1-chloropropane (2)} binary system

The current study reports original vapour-liquid equilibrium (VLE) for the system {CO2 (1)+1-chloropropane (2)}. The measurements have been performed over the entire pressure-composition range for the T=(303.15, 313.15 and 328.15)K isotherms. The values obtained have been used for comparison of four predictive approaches, namely the equation of state (EoS) of Peng and Robinson (PR), the Soave modification of Benedict–Webb–Rubin (SBWR) EoS, the Critical Point-based Revised Perturbed-Chain Association Fluid Theory (CP-PC-SAFT) EoS, and the Conductor-like Screening Model for Real Solvents (COSMO-RS). It has been demonstrated that the three EoS under consideration yield similar and qualitatively accurate predictions of VLE, which is not the case for the COSMO-RS model examined. Although CP-PC-SAFT EoS exhibits only minor superiority in comparison with PR and SBWR EoS in predicting VLE in the system under consideration, its relative complexity can be justified when taking into account the entire thermodynamic phase space and, in particular, considering the liquid densities and sound velocities over a wider pressure-volume-temperature range.

Solubility prediction, solvate and cocrystal screening as tools for rational crystal engineering.

The fact that novel drug candidates are becoming increasingly insoluble is a major problem of current drug development. Computational tools may address this issue by screening for suitable solvents or by identifying potential novel cocrystal formers that increase bioavailability. In contrast to other more specialized methods, the fluid phase thermodynamics approach COSMO-RS (conductor-like screening model for real solvents) allows for a comprehensive treatment of drug solubility, solvate and cocrystal formation and many other thermodynamics properties in liquids. This article gives an overview of recent COSMO-RS developments that are of interest for drug development and contains several new application examples for solubility prediction and solvate/cocrystal screening. For all property predictions COSMO-RS has been used. The basic concept of COSMO-RS consists of using the screening charge density as computed from first principles calculations in combination with fast statistical thermodynamics to compute the chemical potential of a compound in solution. The fast and accurate assessment of drug solubility and the identification of suitable solvents, solvate or cocrystal formers is nowadays possible and may be used to complement modern drug development. Efficiency is increased by avoiding costly quantum-chemical computations using a database of previously computed molecular fragments. COSMO-RS theory can be applied to a range of physico-chemical properties, which are of interest in rational crystal engineering. Most notably, in combination with experimental reference data, accurate quantitative solubility predictions in any solvent or solvent mixture are possible. Additionally, COSMO-RS can be extended to the prediction of cocrystal formation, which results in considerable predictive accuracy concerning coformer screening. In a recent variant costly quantum chemical calculations are avoided resulting in a significant speed-up and ease-of-use.

Alternative bio-based solvents for extraction of fat and oils: solubility prediction, global yield, extraction kinetics, chemical composition and cost of manufacturing.

The present study was designed to evaluate the performance of alternative bio-based solvents, more especially 2-methyltetrahydrofuran, obtained from crop’s byproducts for the substitution of petroleum solvents such as hexane in the extraction of fat and oils for food (edible oil) and non-food (bio fuel) applications. First a solvent selection as well as an evaluation of the performance was made with Hansen Solubility Parameters and the COnductor-like Screening MOdel for Realistic Solvation (COSMO-RS) simulations. Experiments were performed on rapeseed oil extraction at laboratory and pilot plant scale for the determination of lipid yields, extraction kinetics, diffusion modeling, and complete lipid composition in term of fatty acids and micronutrients (sterols, tocopherols and tocotrienols). Finally, economic and energetic evaluations of the process were conducted to estimate the cost of manufacturing using 2-methyltetrahydrofuran (MeTHF) as alternative solvent compared to hexane as petroleum solvent.

Theoretical selection of most effective ionic liquids for liquid–liquid extraction of NdF3

The purpose of this study was to select the most effective ionic liquid (IL) extraction solvents for NdF3 using a theoretical conductor-like screening model for real solvents (COSMO-RS) for predefined NdF3-IL systems.Chemical potentials of NdF3 were predicted in 900 hydrophobic ILs. On the basis of these predictions, a number of IL ions showing a significant decrease in their chemical potentials were selected.Considering the calculated physicochemical properties of ILs containing these specific ions, the most effective IL extraction solvents for liquid–liquid extraction of the salts were proposed.This study shows that the COSMO-RS approach can be applied before conducting extensive experiments to quickly screen the affinity of any rare earth element for many IL 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.

Estimation of ginger bioactive compound solubilities in hot compressed water and enhancement with entrainer

Knowledge concerning the solubility of ginger bioactive compounds in hot compressed water (HCW) is important for designing an extraction process with water as a green solvent. The solubilities of 6-gingerol and 6-shogaol in hot compressed water are calculated using the conductor-like screening model for real solvent (COSMO-RS) method to study the potential of water as a solvent. The comparison indicates that the calculated solubility is at a higher concentration for the binary system of 6-gingerol+water and 6-shogaol+water when compared to the HCW extraction. This illustrates the performance of the HCW extraction, which has not reached the equilibrium condition, and gives an opportunity to explore the options for further improving the process. The availability as well as the thermo-labile nature of the bioactive compounds are factors that must be considered for the improvement of HCW as a solvent. The solubilities of 6-gingerol and 6-shogaol in aqueous ethanol solutions are also calculated by the COSMO-RS method to study the entrainer effect of ethanol. The calculations with ethanol as entrainer indicate that the molecular cavity and contact interaction are changed so as to increase the solubilities. Based on the calculations, the suitable amount of ethanol as an entrainer is estimated to be 0.02mole fraction for both 6-gingerol and 6-shogaol with an improved solubility of 1.86 and 1.76 times, respectively. In general, the addition of the entrainer will improve the recovery and operating parameters at a milder operating condition. This approach may be applied to other bioactives and will further strengthen the use of water as a solvent in natural extracts.