Process Simulation and Optimization on Ionic Liquids.

Ionic liquids (ILs) are promising alternative compounds that enable the development of technologies based on their unique properties as solvents or catalysts. These technologies require integrated product and process designs to select ILs with optimal process performances at an industrial scale to promote cost-effective and sustainable technologies. The digital era and multiscale research methodologies have changed the paradigm from experiment-oriented to hybrid experimental-computational developments guided by process engineering. This Review summarizes the relevant contributions (>300 research papers) of process simulations to advance IL-based technology developments by guiding experimental research efforts and enhancing industrial transferability. Robust simulation methodologies, mostly based on predictive COSMO-SAC/RS and UNIFAC models in Aspen Plus software, were applied to analyze key IL applications: physical and chemical CO2 capture, CO2 conversion, gas separation, liquid-liquid extraction, extractive distillation, refrigeration cycles, and biorefinery. The contributions concern the IL selection criteria, operational unit design, equipment sizing, technoeconomic and environmental analyses, and process optimization to promote the competitiveness of the proposed IL-based technologies. Process simulation revealed that multiscale research strategies enable advancement in the technological development of IL applications by focusing research efforts to overcome the limitations and exploit the excellent properties of ILs.

Design of Ionic Liquids for Fluorinated Gas Absorption: COSMO-RS Selection and Solubility Experiments.

In recent years, the fight against climate change and the mitigation of the impact of fluorinated gases (F-gases) on the atmosphere is a global concern. Development of technologies that help to efficiently separate and recycle hydrofluorocarbons (HFCs) at the end of the refrigeration and air conditioning equipment life is a priority. The technological development is important to stimulate the F-gas capture, specifically difluoromethane (R-32) and 1,1,1,2-tetrafluoroethane (R-134a), due to their high global warming potential. In this work, the COSMO-RS method is used to analyze the solute-solvent interactions and to determine Henry's constants of R-32 and R-134a in more than 600 ionic liquids. The three most performant ionic liquids were selected on the basis of COSMO-RS calculations, and F-gas absorption equilibrium isotherms were measured using gravimetric and volumetric methods. Experimental results are in good agreement with COSMO-RS predictions, with the ionic liquid tributyl(ethyl)phosphonium diethyl phosphate, [P2444][C2C2PO4], being the salt presenting the highest absorption capacities in molar and mass units compared to salts previously tested. The other two ionic liquids selected, trihexyltetradecylphosphonium glycinate, [P66614][C2NO2], and trihexyl(tetradecyl)phosphonium 2-cyano-pyrrole, [P66614][CNPyr], may be competitive as far as their absorption capacities are concerned. Future works will be guided on evaluating the performance of these ionic liquids at an industrial scale by means of process simulations, in order to elucidate the role in process efficiency of other relevant absorbent properties such as viscosity, molar weight, or specific heat.

Process Evaluation of Fluorinated Ionic Liquids as F-Gas Absorbents.

The environmental impact of fluorinated gases (F-gases) necessitates the development of green technologies to mitigate them. Fluorinated ionic liquids (FIL/ILs) emerged as an alternative absorbent due to their unique and exceptional properties. In this work, a COSMO-based/Aspen Plus methodology was used to evaluate the performance of FIL/ILs as absorbents in the process scale of two F-gases: 1,1,1,2-tetrafluoroethane (R-134a) and difluoromethane (R-32). Results of the absorption column in equilibrium mode revealed that the behavior of FIL/ILs is similar under the same conditions, reaching higher efficiencies in the case of absorbing R-134a at a high F-gas partial pressure. Rate-based calculations in packing column demonstrated a kinetic control with highly viscous FIL/ILs, revealing higher performance differences between FIL/IL absorbents. The regeneration stage was also evaluated in near-industrial conditions. Operating conditions of the absorption column were optimized with a column of height 10 m and diameter ranging from 1.1 to 1.2 m at 10 bar total pressure, reaching 90% F gas recovery with an L/G range of 6-10. Finally, preliminary economic analysis revealed operating costs to recover 90% of F-gas of 70 $/ton (R-134a) and 130 $/ton (R-32) with the FIL/IL that revealed the best behavior, 1-ethyl-3-methylimidazolium triflate.

Methanol-Promoted Oxidation of Nitrogen Oxide (NOx) by Encapsulated Ionic Liquids.

The removal of nitrogen oxides (NOx) has been extensively studied due to their harmful effects to health and environment. In this work, encapsulated ionic liquids (ENILs) are used as catalysts for the NO oxidation at humid conditions and low temperatures. Hollow carbon capsules (CCap) were first synthesized to contain different amounts of 1-butyl-3-methylimidazolium nitrate IL ([bmim][NO3]), responsible for the catalytic oxidation. Then, the materials were characterized using different techniques, by analyzing microstructure, porosity, elemental composition, and thermal stability. The catalytic performance of ENIL materials was tested for NO conversion at different conditions. Thus, NO concentration was fixed at 2000 ppm at dry and humid conditions. Then, the methanol promotion of the reaction was demonstrated, increasing the NO conversion values in all cases, and the alcohol/water ratio was optimized. The temperature effect was studied as well, using the optimal conditions based on the previous measurements. The results reflect that humid conditions do not have a negative effect in terms of NO conversion when using ENILs, opposite behavior as observed for CCap and traditional catalysts studied before. The low amount of IL inside the material (40% in mass) was found to be the optimum for the task, reaching conversions of almost 45% in near industrial conditions of temperature and O2 and H2O concentrations in the flue gas with a GHSV of 10,000 h-1.

Molecular and Thermodynamic Properties of Zwitterions versus Ionic Liquids: A Comprehensive Computational Analysis to Develop Advanced Separation Processes.

Zwitterion ionic liquids (ZIs) are compounds in which both counterions are covalently tethered, conferring them with unique characteristics; however, most of their properties are still unknown, representing a bottleneck to exploit their practical applications. Herein, the molecular and fluid properties of ZIs and their mixtures were explored by means of quantum chemical analysis based on the density functional theory (DFT) and COSMO-RS method, and compared against homologous ionic liquids (ILs) to provide a comprehensive overview of the effect of the distinct structures on their physicochemical and thermodynamic behavior. Overall, ZIs were revealed as compounds with higher polarity and stronger hydrogen-bonding capacity, implying higher density, viscosity, melting point, and even lower volatility than structurally similar ILs. The phase equilibrium of binary and ternary systems supports stronger attractive interactions between ZIs and polar compounds, whereas higher liquid-liquid immiscibility with nonpolar compounds may be expected. Ultimately, the performance of ZIs in the wider context of separation processes is illustrated, while providing molecular insights to allow their selection and design for relevant applications.

Intensification of Basal Insulin Therapy with Lixisenatide in Patients with Type 2 Diabetes in a Real-World Setting: The BASAL-LIXI Study.

BACKGROUND: Basal insulin reduces fasting blood glucose levels, but postprandial blood glucose levels may remain higher. Traditional strategies with rapid insulin intensification can cause hypoglycemic episodes and weight gain. Glucagon-like peptide-1 receptor agonists, such as the short-acting lixisenatide, are able to control postprandial excursions, without weight gain, and with a low risk of hypoglycemic events. OBJECTIVE: Due to the limited data on the combination of lixisenatide with basal insulin (with or without oral antidiabetes drugs) in clinical practice, this study evaluated changes in parameters associated with glycemic control and anthropometric data after 24 weeks of this therapy intensification. METHODS: This was a multicenter, retrospective observational study of 129 patients with type 2 diabetes that was uncontrolled by basal insulin. Their treatment was intensified by the addition of lixisenatide at least 24 weeks before being included in the study. Data were retrospectively collected to determine changes in glycated hemoglobin (HbA1c) levels, blood glucose levels, weight, and body mass index. Adverse reactions and hypoglycemic events were also recorded. RESULTS: After 24 weeks of therapy intensification with lixisenatide, a significant reduction in HbA1c levels was observed (-1.1%; P < 0.001). An HbA1c <7% was achieved in 30.2% of patients, and 17.1% reached an HbA1c <6.5%. There was a reduction in fasting blood glucose (31.8 [60.3] mg/dL; P < 0.001) and postprandial blood glucose (55.0 [49] mg/dL; P < 0.001) levels, as well as body weight (4.0 [5.4] kg; P < 0.001) and body mass index (1.5 [1.9]; P < 0.001). The most commonly observed adverse reactions were nausea (n = 9), in line with previous studies. Hypoglycemia events were rare; only reported in 2 patients. CONCLUSIONS: Intensification strategy based on lixisenatide added to basal insulin (with or without oral antidiabetes drugs) can be an effective treatment option in patients with uncontrolled type 2 diabetes. In this small, selected population, glycemic control was significantly improved in terms of HbA1, fasting blood glucose levels, and postprandial glucose levels, with a reduction of body weight and low risk of hypoglycemic events. (Curr Ther Res Clin Exp. 2018; 79:XXX-XXX).

Encapsulated Ionic Liquids for CO2 Capture: Using 1-Butyl-methylimidazolium Acetate for Quick and Reversible CO2 Chemical Absorption.

The potential advantages of applying encapsulated ionic liquid (ENIL) to CO2 capture by chemical absorption with 1-butyl-3-methylimidazolium acetate [bmim][acetate] are evaluated. The [bmim][acetate]-ENIL is a particle material with solid appearance and 70 % w/w in ionic liquid (IL). The performance of this material as CO2 sorbent was evaluated by gravimetric and fixed-bed sorption experiments at different temperatures and CO2 partial pressures. ENIL maintains the favourable thermodynamic properties of the neat IL regarding CO2 absorption. Remarkably, a drastic increase of CO2 sorption rates was achieved using ENIL, related to much higher contact area after discretization. In addition, experiments demonstrate reversibility of the chemical reaction and the efficient ENIL regeneration, mainly hindered by the unfavourable transport properties. The common drawback of ILs as CO2 chemical absorbents (low absorption rate and difficulties in solvent regeneration) are overcome by using ENIL systems.

Enhancing the adsorption of ionic liquids onto activated carbon by the addition of inorganic salts.

Most ionic liquids (ILs) are either water soluble or present a non-negligible miscibility with water that may cause some harmful effects upon their release into the environment. Among other methods, adsorption of ILs onto activated carbon (AC) has shown to be an effective technique to remove these compounds from aqueous solutions. However, this method has proved to be viable only for hydrophobic ILs rather than for the hydrophilic that, being water soluble, have a larger tendency for contamination. In this context, an alternative approach using the salting-out ability of inorganic salts is here proposed to enhance the adsorption of hydrophilic ILs onto activated carbon. The effect of the concentrations of Na2SO4 on the adsorption of five ILs onto AC was investigated. A wide range of ILs that allow the inspection of the IL cation family (imidazolium- and pyridinium-based) and the anion nature (accounting for its hydrophilicity and fluorination) through the adsorption onto AC was studied. In general, it is shown that the use of Na2SO4 enhances the adsorption of ILs onto AC. In particular, this effect is highly relevant when dealing with hydrophilic ILs that are those that are actually poorly removed by AC. In addition, the COnductor like Screening MOdel for Real Solvents (COSMO-RS) was used aiming at complementing the experimental data obtained. This work contributes with the development of novel methods to remove ILs from water streams aiming at creating "greener" processes.

[Improving the nutritional care of oncology patients - Validation of a multidisciplinary protocol in the Spanish clinical setting]. / Mejorando la atención nutricional del paciente oncológico: validación de un protocolo multidisciplinar en el entorno clínico español.

Introduction: Introduction: malnutrition is a very frequent problem in oncology patients and may have serious repercussions. Adequate nutritional management is cost-effective in terms of health and survival in this population, but it requires multidisciplinary coordination, specific training, and continuous follow-up. Objective: to validate the applicability and efficacy of a multidisciplinary nutritional support protocol in oncology patients. Methods: a multidisciplinary nutritional protocol was developed for oncology patients, with guidelines for screening and assessment of malnutrition, treatment, re-evaluation, and management of side effects, as well as guidance on supplementation and eating patterns. The protocol would be implemented in various clinical centers, collecting data through a structured questionnaire, registering variables before and after implementation. Results: the protocol and its impact were implemented and evaluated in 39 centers. An improvement in nutritional care was observed, evidenced by an earlier initiation of nutritional assessment and an increase in the number of patients receiving adequate care following the protocol implementation. Problems related to inadequate malnutrition coding in the centers, limited resources, and the need for greater interdepartmental collaboration were identified. Conclusions: the conduct of this study provides insights into how the implementation of a multidisciplinary nutritional support protocol can improve the nutritional care received by patients and informs about the main obstacles to adequate implementation.

Introducción: Introducción: la desnutrición es un problema muy frecuente en el paciente oncológico y puede tener graves repercusiones. Un manejo nutricional adecuado es coste-efectivo en términos de salud y supervivencia en esta población, pero requiere de coordinación multidisciplinar, formación específica y seguimiento continuo. Objetivo: validar la aplicabilidad y eficacia de un protocolo multidisciplinar de soporte nutricional en pacientes oncológicos. Métodos: se desarrolló un protocolo nutricional multidisciplinar para pacientes oncológicos, con pautas para el cribado y valoración de la desnutrición, el tratamiento, la reevaluación y la gestión de los efectos secundarios, además de orientaciones sobre suplementación y patrones de alimentación. Se implementaría el protocolo en diversos centros clínicos, recogiendo datos a través de un cuestionario estructurado, registrando variables antes y después de la implementación. Resultados: se implementó y se valoraron el protocolo y su impacto en 39 centros. Se observó una mejoría en la atención nutricional, evidenciada por un inicio más precoz de la valoración nutricional y un aumento en el número de pacientes que recibían atención adecuada tras la implementación del protocolo. Se identificaron problemas relacionados con una inadecuada codificación de la desnutrición en los centros, recursos limitados y la necesidad de mayor colaboración interdepartamental. Conclusiones: la realización de este estudio ofrece información de cómo la implementación de un protocolo multidisciplinar de soporte nutricional puede contribuir a mejorar la atención nutricional que reciben los pacientes e informa de cuáles son los principales obstáculos para una implementación adecuada.

COSMO-RS analysis on mixing properties obtained for the systems 1-butyl-X-methylpyridinium tetrafluoroborate [X = 2,3,4] and 1,ω-dibromoalkanes [ω = 1-6].

A theoretical-experimental study for a set of 18 binary systems comprised of [bXmpy][BF(4)] (X=2-4) + 1,ω-Br(CH(2))(v)Br (v =ω=1-6) at a temperature of 298.15 K is presented. The solubility curves are determined for each binary system, establishing the intervals of measurement for the excess properties, H(E)(m) and V(E)(m). These properties are then determined for those systems that present a miscibility zone. Binary systems containing 1,ω-dibromoalkanes with ω=5,6 present reduced solubility intervals at the temperature of 298.15 K. However, the mixtures with 1,1-dibromomethane were totally miscible with the three isomers of 1-butyl-X-methylpyridinium tetrafluoroborate. Mixtures with dibromomethane present H(E)(m) <0, whereas H(E)(m) >0 for the other binary systems. Sigmoidal curves were observed for the V(E)(m) describing expansion and contraction processes for all the systems, except for the mixtures of [b2mpy][BF(4)] with the smaller dibromoalkanes, which present contraction effects. The COSMO-RS methodology was used to estimate the solubilities and the intermolecular interaction energies, giving an acceptable explanation of the behavioral structure of pure compounds and solutions.

A COSMO-RS based guide to analyze/quantify the polarity of ionic liquids and their mixtures with organic cosolvents.

A COSMO-RS descriptor (S(sigma-profile)) has been used in quantitative structure-property relationship (QSPR) studies by a neural network (NN) for the prediction of empirical solvent polarity E(T)(N) scale of neat ionic liquids (ILs) and their mixtures with organic solvents. S(sigma-profile) is a two-dimensional quantum chemical parameter which quantifies the polar electronic charge of chemical structures on the polarity (sigma) scale. Firstly, a radial basis neural network exact fit (RBNN) is successfully optimized for the prediction of E(T)(N), the solvatochromic parameter of a wide variety of neat organic solvents and ILs, including imidazolium, pyridinium, ammonium, phosphonium and pyrrolidinium families, solely using the S(sigma-profile) of individual molecules and ions. Subsequently, a quantitative structure-activity map (QSAM), a new concept recently developed, is proposed as a valuable tool for the molecular understanding of IL polarity, by relating the E(T)(N) polarity parameter to the electronic structure of cations and anions given by quantum-chemical COSMO-RS calculations. Finally, based on the additive character of the S(sigma-profile) descriptor, we propose to simulate the mixture of IL-organic solvents by the estimation of the S(sigma-profile)(Mixture) descriptor, defined as the weighted mean of the S(sigma-profile) values of the components. Then, the E(T)(N) parameters for binary solvent mixtures, including ILs, are accurately predicted using the S(sigma-profile)(Mixture) values from the RBNN model previously developed for pure solvents. As result, we obtain a unique neural network tool to simulate, with similar reliability, the E(T)(N) polarity of a wide variety of pure ILs as well as their mixtures with organic solvents, which exhibit significant positive and negative deviations from ideality.

Photostability and photocatalytic degradation of ionic liquids in water under solar light.

The aim of this work is to study, (i) the photostability of different imidazolium and pyridinium ionic liquids (ILs) in water under solar light; and (ii) the photocatalytic degradation of those ILs in water with TiO2 under solar light. The effects of the type of cation and anion as well as the length of the cationic chain of the imidazolium ILs have been analyzed. These imidazolium-based ILs show high solar stability, slightly decreasing as the length of the cationic chain increases. The anion plays a main role in the stability of ILs under solar light, decreasing in the case of hydrophobic anions. The kind of head group (pyridinium or imidazolium) or the presence of functional groups (allyl, OH) also influence the solar light stability. DFT calculations on the fundamental and excited electronic states of the ILs were carried out to obtain a deeper insight on their photostability. In the case of the photocatalytic degradation of the ILs, complete conversion was achieved for all the ILS tested but mineralization reached 80% at the most. The rate of degradation increased with the length of the alkyl chain while the anion showed little effect. The pyridinium-based IL tested was the easiest to breakdown.

Encapsulation of Ionic Liquids with an Aprotic Heterocyclic Anion (AHA-IL) for CO2 Capture: Preserving the Favorable Thermodynamics and Enhancing the Kinetics of Absorption.

The performance of an ionic liquid with an aprotic heterocyclic anion (AHA-IL), trihexyl(tetradecyl)phosphonium 2-cyanopyrrolide ([P66614][2-CNPyr]), for CO2 capture has been evaluated considering both the thermodynamics and the kinetics of the phenomena. Absorption gravimetric measurements of the gas-liquid equilibrium isotherms of CO2-AHA-IL systems were carried out from 298 to 333 K and at pressures up to 15 bar, analyzing the role of both chemical and physical absorption phenomena in the overall CO2 solubility in the AHA-IL, as has been done previously. In addition, the kinetics of the CO2 chemical absorption process was evaluated by in situ Fourier transform infrared spectroscopy-attenuated total reflection, following the characteristic vibrational signals of the reactants and products over the reaction time. A chemical absorption model was used to describe the time-dependent concentration of species involved in the reactive absorption, obtaining kinetic parameters (such as chemical reaction kinetic constants and diffusion coefficients) as a function of temperatures and pressures. As expected, the results demonstrate that the CO2 absorption rate is mass-transfer-controlled because of the relatively high viscosity of AHA-IL. The AHA-IL was encapsulated in a porous carbon sphere (Encapsulated Ionic Liquid, ENIL) to improve the kinetic performance of the AHA-IL for CO2 capture. The newly synthesized AHA-ENIL material was evaluated as a CO2 sorbent with gravimetric absorption measurements. AHA-ENIL systems preserve the good CO2 absorption capacity of the AHA-IL but drastically enhance the CO2 absorption rate because of the increased gas-liquid surface contact area achieved by solvent encapsulation.

Computational approach to nuclear magnetic resonance in 1-Alkyl-3-methylimidazolium ionic liquids.

A quantum-chemical computational approach to accurately predict the nuclear magnetic resonance (NMR) properties of 1-alkyl-3-methylimidazolium ionic liquids has been performed by the gauge-including atomic orbitals method at the B3LYP/6-31++G** level using different simulated ionic liquid environments. The first molecular model chosen to describe the ionic liquid system includes the gas-phase optimized structures of ion pairs and separated ions of a series of imidazolium salts containing methyl, butyl, and octyl substituents and PF6-, BF4-, and Br- anions. In addition, a continuum polarizable model of solvation has been applied to predict the effects of the medium polarity on the molecular properties of 1,3-dimethylimidazolium hexafluorophosphate (MmimPF6). Furthermore, the specific acidic and basic solute-solvent interactions have been simulated by a discrete solvation model based on molecular clusters formed by MmimPF6 species and a discrete number of water molecules. The computational prediction of the NMR spectra allows a consistent interpretation of the dispersed experimental evidence in the literature. The following are main contributions of this work: (a) Theoretical results state the presence of a chemical equilibrium between ion-pair aggregates and solvent-separated counterions of 1-alkyl-3-methylimidazolium salts which is tuned by the solvent environment; thus, strong specific (acidic and basic) and nonspecific (polarity and polarizability) solvent interactions are predicted favoring the dissociated ionic species. (b) The calculated 1H and 13C NMR properties of these ionic liquids are revealed as highly dependent on the nature of solute-solvent interactions. Thus, the chemical shift of the hydrogen atom in position two of the imidazolium ring is deviated to high values by the specific interactions with water molecules, whereas nonspecific interaction with water (as a solvent) affects, in the opposite direction, this 1H NMR parameter. (c) Last, current calculations support the presence of hydrogen bonding between counterions, suggesting the importance of this interaction in the properties of the solvent in the 1-alkyl-3-methylimidazolium ionic liquids.

Description of the behavior of dichloroalkanes-containing solutions with three [bXmpy][BF4] isomers, using the experimental information of thermodynamic properties, 1H NMR spectral and the COSMO-RS-methodology.

This work studies the binaries of 1-butyl-X-methylpyridinium tetrafluoroborate [bXmpy][BF4] (X = 2, 3, and 4) with four 1,ω-dichloroalkanes, ω = 1-4, using the results obtained for the mixing properties h(E) and v(E) at two temperatures. The three isomers of the ionic liquid (IL) are weakly miscible with the 1,ω-dichloroalkanes when ω ≥ 5 and moderately soluble for ω = 4. The v(E)s of all the binaries present contractive effects, v(E) < 0, which are more pronounced with increasing temperature; the variation in v(E) with ω is positive, although this changes after ω = 4 due to problems of immiscibility. The energetic effects of the mixing process are exothermic in the solutions with the shorter dichloroalkanes, ω = 1 and 2, and this effect increases slightly with temperature. However, mildly exothermic effects are found in the binaries with larger halides, where (dh(E)/dT) > 0. The experimental data are correlated with a suitable equation. The study is completed with (1)H NMR measurements of both the pure compounds and some of the solutions, which showed minor diamagnetic shifts with increasing IL compositions, related to the anisotropy of the pyridine ring. The variation in h(E) with ω for a same IL, due to an increase in the contact surfaces, is related to the reduction in polarity which, in turn, depends on the smaller chemical shifts of the pure dihalide compounds. The COSMO-RS method determines the energetic effects of the mixing process and predicts an exothermic contribution for the electrostatic Misfit-interaction which is quantitatively very similar for the three IL isomers. The differences proposed by the model are mainly reflected in the van der Waals interactions, which are exothermic and clearly influenced by the position of the methylene group in the IL. The contribution made by hydrogen bonds is negligible.

Ionic liquid mixtures--an analysis of their mutual miscibility.

The use of ionic liquid mixtures (IL-IL mixtures) is being investigated for fine solvent properties tuning of the IL-based systems. The scarce available studies, however, evidence a wide variety of mixing behaviors (from almost ideal to strongly nonideal), depending on both the structure of the IL components and the property considered. In fact, the adequate selection of the cations and anions involved in IL-IL mixtures may ensure the absence or presence of two immiscible liquid phases. In this work, a systematic computational study of the mixing behavior of IL-IL systems is developed by means of COSMO-RS methodology. Liquid-liquid equilibrium (LLE) and excess enthalpy (H(E)) data of more than 200 binary IL-IL mixtures (including imidazolium-, pyridinium-, pyrrolidinium-, ammonium-, and phosphonium-based ILs) are calculated at different temperatures, comparing to literature data when available. The role of the interactions between unlike cations and anions on the mutual miscibility/immiscibility of IL-IL mixtures was analyzed. On the basis of proposed guidelines, a new class of immiscible IL-IL mixtures was reported, which only is formed by imidazolium-based compounds.

Excess enthalpy of monoethanolamine + ionic liquid mixtures: how good are COSMO-RS predictions?

Mixtures of ionic liquids (ILs) and molecular amines have been suggested for CO2 capture applications. The basic idea is to replace water, which volatilizes in the amine regeneration step and increases the parasitic energy load, with a nonvolatile ionic liquid solvent. To fully understand the thermodynamics of these systems, here experimental excess enthalpies for binary mixtures of monoethanolamine (MEA) and two ILs: 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [hmim][NTf2], and 1-(2-hydroxyethyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [OHemim][NTf2], were obtained by calorimetry, using a Setaram C80 calorimeter, over the whole range of compositions at 313.15 K. Since it is the temperature derivative of the Gibbs energy, enthalpy is a sensitive measure of intermolecular interactions. MEA + [hmim][NTf2] is endothermic and MEA + [OHemim][NTf2] is exothermic. The reliability of COSMO-RS to predict the excess enthalpy of the (MEA+IL) systems was tested based on the implementation of two different molecular models to define the structure of the IL: the IL as separate cation and anion [C+A] and the IL as a bonded single specie [CA]. Quantum-chemical calculations were performed to gain additional insight into the intermolecular interactions between the components of the mixture. For MEA + [hmim][NTf2] both the [C+A] and [CA] models predict endothermic behavior, but the [CA] model is in better agreement with the experimental results. For MEA + [OHemim][NTf2] the [C+A] model provides the best match to the experimental exothermic results. However, what is really surprising is that two different conformations of the cation-anion pair with nearly identical energies in the [CA] model result in completely different (exothermic vs endothermic) predictions of the excess enthalpy. Nonetheless, the results do show that the influence of the structure of the IL on the thermodynamic behavior of the mixture (endothermic vs exothermic) can be attributed to hydrogen bonding between the cation and the MEA molecule. However, this study highlights the importance of carefully selecting the molecular model and conformation in order to obtain even qualitatively correct predictions with COSMO-RS. The fact that even very slightly different conformations of the IL can drastically change the thermodynamic estimations using COSMO-RS is of significant concern. Overall, we believe the present work provides a better understanding of the behavior of mixtures involving amines and ILs, which is an important aspect to consider when evaluating the use of such solvent mixtures in CO2 capture technologies.

Selection of ionic liquids for enhancing the gas solubility of volatile organic compounds.

A systematic thermodynamic analysis has been carried out for selecting cations and anions to enhance the absorption of volatile organic compounds (VOCs) at low concentration in gaseous streams by ionic liquids (ILs), using COSMO-RS methodology. The predictability of computational procedure was validated by comparing experimental and COSMO-RS calculated Henry's law constant data over a sample of 125 gaseous solute-IL systems. For more than 2400 solute-IL mixtures evaluated, including 9 solutes and 270 ILs, it was found that the lower the activity coefficient at infinite dilution (γ(∞)) of solutes in the ILs, the more the exothermic excess enthalpy (H(E)) of the equimolar IL-solute mixtures. Then, the solubility of a representative sample of VOC solutes, with very different chemical nature, was screened in a wide number of ILs using COSMO-RS methodology by means of γ(∞) and H(E) parameters, establishing criteria to select the IL structures that promote favorable solute-solvent intermolecular interactions. As a result of this analysis, an attempt of classification of VOCs respect to their potential solubility in ILs was proposed, providing insights to rationally select the cationic and anionic species for a possible development of absorption treatments of VOC pollutants based on IL systems.

Anion effects on kinetics and thermodynamics of CO2 absorption in ionic liquids.

A thermogravimetric technique based on a magnetic suspension balance operating in dynamic mode was used to study the thermodynamics (in terms of solubility and Henry's law constants) and kinetics (i.e., diffusion coefficients) of CO2 in the ionic liquids [bmim][PF6], [bmim][NTf2], and [bmim][FAP] at temperatures of 298.15, 308.15, and 323.15 K and pressures up to 20 bar. The experimental technique employed was shown to be a fast, accurate, and low-solvent-consuming method to evaluate the suitability of the ionic liquids (ILs) to be used as CO2 absorbents. Thermodynamic results confirmed that the solubility of CO2 in the ILs followed the order [bmim][FAP] > [bmim][NTf2] > [bmim][PF6], increasing with decreasing temperatures and increasing pressures. Kinetic data showed that the diffusion coefficients of CO2 in the ILs followed a different order, [bmim][NTf2] > [bmim][FAP] > [bmim][PF6], increasing with increasing temperatures and pressures. These results evidenced the different influence of the IL structure and operating conditions on the solubility and absorption rate of CO2, illustrating the importance of considering both thermodynamic and kinetic aspects to select adequate ILs for CO2 absorption. On the other hand, the empirical Wilke-Chang correlation was successfully applied to estimate the diffusion coefficients of the systems, with results indicating the suitability of this approach to foresee the kinetic performance of ILs to absorb CO2. The research methodology proposed herein might be helpful in the selection of efficient absorption solvents based on ILs for postcombustion CO2 capture.