COSMO-SAC Model Research Articles

Vapor–liquid equilibrium for protic ionic liquids and water: [BA][Pr], [DEA][Pr], [m-2HEA][Pr] and [e-2HEA][Pr

Over the last decade, research on ionic liquids (ILs) has shown a significant increase, but phase equilibria data for many systems is still scarce. In this study, vapor–liquid equilibria was measured for water in four protic ionic liquids (PILs), namely: butylammonium propionate ([BA][Pr]), diethylammonium propionate ([DEA][Pr]), N-methyl-2-hydroxyethylammonium propionate ([m-2HEA][Pr]) and N-ethyl-2-hydroxyethylammonium propionate ([e-2HEA][Pr]). The experimental data were measured using the hygrometric method at the temperature range from 293 K to 313 K. In addition, NRTL model parameters were estimated using VLE data. It was possible to use a single parameter set to represent all temperatures with an average deviation of 5.0 %. All water–PILs systems investigated have shown negative deviations to ideality. The predictive capacity of COSMO-SAC model was checked by comparing its response with the measured experimental data. In general, semi-quantitative agreement was observed between the experimental values and COSMO-SAC predictions, indicating that the model can be an alternative for such systems in the absence of experimental information.

Separation of n-hexane-ethanol azeotropic mixture using choline chloride +1,4-butanediol deep eutectic solvents

For an environmentally friendly and economical separation process of ethanol from n-hexane which is hard to handle due to the azeotrope, the liquid-liquid extraction was carried out by using choline chloride (ChCl) based deep eutectic solvents (DESs) in different molar ratios with 1,4-butanediol: DES1 (ChCl:1,4-butanediol=1:3), DES2 (ChCl:1,4-butanediol=1:4), and DES3 (ChCl:1,4-butanediol=1:5). The liquid-liquid phase equilibrium was performed on the n-Hexane (1) + Ethanol (2) + DES (3) systems at 298.15 K and atmospheric pressure. The binodal curve is determined by using the turbidity method. The various physico-chemical properties such as refractive index, viscosity, and density were measured for compositions in the binodal point. The equilibrium compositions of liquid-liquid phase equilibrium were determined from the refractive index value at the binodal points, and were predicted by COSMO-SAC model. The miscibility area predicted by COSMO-SAC model became larger as the molar ratio of 1,4-butanediol in DES increased, that is, DES3 shows the most miscible area. While in the experimental results, the miscibility depending on DES-type does not show a large difference. The experimental values for PI shows the order of DES2 (ChCl:1,4-butanediol=1:4)> DES1 (ChCl:1,4-butanediol=1:3)> DES3 (ChCl:1,4-butanediol=1:5) at less 3 wt% concentration of ethanol, but at higher concentration range (>3 wt%) DES3 shows the best value. Both of DES2 and DES3 are profitable to adopt in the extraction process of ethanol from n-hexane owing to the high performance index, high distribution coefficient, and high selectivity. The experimental results show the possibility of DESs as an alternative to ionic liquids in the separation of azeotropic mixtures, taking into account the properties of DES such as low price, uncomplicated manufacturing methods, environmentally friendly, and low toxicity.

Mechanism analysis and liquid-liquid equilibrium of methyl tert-butyl ether separation from petroleum wastewater azeotrope by green mixed solvent

Petroleum wastewater contains large amounts of methyl tert-butyl ether (MTBE) and ethanol azeotropes. Efficiently and cleanly separating these azeotropes while conserving energy and reducing the emission of petroleum wastewater is an urgent problem that needs to be solved. In this work, the process of extracting MTBE from petroleum wastewater with water and ionic liquids (ILs) mixed extractant was clarified, and a complete method of evaluating the extraction performance based on the COSMO-SAC model, liquid-liquid extraction measurement, and micro-scale analysis mechanism is proposed. The COSMO-SAC model was used to determine organic solvents and ILs with the best extraction performance from among more than 250 ILs. A mixed solvent of water and the IL 1-ethyl-2,3-dimethylimidazolium ethylsulfate ([EMMIM][EtSO4]) at different molar ratios was selected for the liquid-liquid extraction experiment. It was found that the distribution coefficients and selectivity were maximum when the molar ratio of [EMMIM][EtSO4] to water was 1:2. Combined with molecular dynamics simulations and quantum chemical calculations, the interaction mechanisms of different solvents with MTBE and ethanol were revealed on the micro-level. This work provides a prototype for the high-efficiency extraction of MTBE from petroleum wastewater using a new mixed solvent of ILs and water, and it provides an application prospect for the efficient and green recycling of MTBE.

Modified version of the COSMO-SAC model for the prediction of vapour-liquid equilibria of mixtures containing halogen compounds

• COSMO-SAC (+OH-Cl), (+OH-Br) and (+OH-ClBr), extensions of the COSMO-SAC model were developed to take into account hydrogen bonds formed with chlorine or bromine atoms, in particular in mixtures containing deep eutectic solvents and water, alcohols or carboxylic acids. • The new parameters of the extended models were optimized with a data base of 1402 vapour-liquid data points. • Performances were tested with vapour-liquid, liquid-liquid and solid-liquid databases with 2237, 787 and 503 data points, respectively. • Improvements of the prediction of the vapour-liquid equilibria for mixture containing halogens atoms were obtained. • Comparisons between the results from the three extended models showed that the distinction between chlorine and bromine atoms in terms of hydrogen bonds was not necessary within the COSMO-SAC models. In this work, the prediction of the phase behaviour of mixtures containing chlorine or bromine atoms involved in hydrogen bonding is investigated. Based on the COSMO-SAC (2010) model, extended models named COSMO-SAC (+OH-Cl), COSMO-SAC (+OH-Br) and COSMO-SAC (+OH-ClBr) are presented. The extension of the base model focuses on the hydrogen bond contribution. For this contribution, the addition of two parameters in an empirical equation introduces a dependence in temperature. The parameters were optimized using a databased composed of vapour-liquid equilibria data of mixtures comprised of both ionic liquids or deep eutectic solvents and regular compounds. The mixtures always involve halides or halocarbons as well as molecules of water, alcohol or carboxylic acids. The extended models are shown to improve the predictions of such systems for vapour-liquid equilibria as well as being able to keep providing satisfying results for both liquid-liquid and solid-liquid equilibria.

Beyond activity coefficients with pairwise interacting surface (COSMO-type) models

Pairwise interacting surface models, like COSMO-RS and COSMO-SAC, are getting popular in the prediction of activity coefficients when experimental data is scarce. In this work an alternative derivation of the COSMO-SAC model is presented and pair contact probabilities as well as nonrandom factors are compared with classic models. By using these probabilities one can readily calculate the system internal energy (or enthalpy). The case of temperature dependent interaction energies and the potential inconsistencies in this case are discussed in detail. Many properties of the resulting equations are discussed, including the issue of distinguishable or indistinguishable segment types. An accompanying open-source code favoring readability over efficiency is also provided.

Separation of ethyl acetate and ethanol by imidazole ionic liquids based on mechanism analysis and liquid–liquid equilibrium experiment

Azeotrope of ethyl acetate (EAC) and ethanol (EA) generated in the synthesis of ethyl acetate (EAC), was difficult to separate by general distillation. Liquid-liquid extraction using ionic liquids (ILs) as extractants is a green and efficient method for separating azeotropes. To select the suitable ILs, the σ-profiles of EAC, EA, and different anions of imidazole ILs were obtained through the COSMO-SAC model. Then, the extraction mechanism of ILs in the EAC-EA system was discussed from the micro perspective, the interaction between ILs and EA was analyzed graphically by the interaction region indicator (IRI) using the Multiwfn and VMD, the interaction energy between ILs and EA/EAC were calculated by Gaussian 09. Finally, we selected 1-ethyl-3-methyl-imidazolium dihydrogen phosphate ([EMIm][H2PO4]), 1-butyl-3-methyl-imidazolium dihydrogen phosphate ([BMIim][H2PO4]), 1-ethyl-3- methyl-imidazolium hydrogen sulfate ([EMIm][HSO4]), and 1-butyl-3-methyl- imidazolium hydrogen sulfate ([BMIm][HSO4]) as the extractants based on the mechanism analysis. The Liquid-liquid equilibrium(LLE) data of EAC-EA-ILs were measured at 298.15 K under atmospheric pressure; the effects of ILs with different alkyl chain lengths of cations on the extraction efficiency were investigated, and the influence of ILs with different anions was also verified through experiments. Meanwhile, we adopted the NRTL activity coefficient equation to regress the experiment data, and the interaction parameters were optimized by the least square method using Matlab 2014.

Investigation on energy-saving extractive distillation for recovering ethanol and 1,4-dioxane from wastewater

Energy-saving extractive distillation for separating ethanol and 1,4-dioxane from the industrial effluent is proposed. From the point of COSMO-SAC model and thermodynamic insights, appropriate entrainer is screened. Ethylene glycol (EG) is chosen in direct extractive distillation process. Subsequently, it is observed that increasing the pressure can make the azeotropic point of ethanol and 1,4-dioxane disappear. Thus, both EG and dimethyl sulfoxide (DMSO) are used as entrainers in indirect extractive distillation (IED) process. The entropy generation of different sections of each column is analyzed. And then, heat integration and heat pump technologies are used to reduce more energy consumption. The comparison results show that the total annual cost (TAC), total energy consumption, CO2 emissions and entropy generation of IED process with DMSO as entrainer (IED-DMSO) is smaller than those processes with EG as entrainer. The IED-DMSO process in combination with heat integration performs best, the TAC is reduced by 41.96%, energy consumption is reduced by 50.28%, CO2 emissions is decreased by 50.28% and entropy generation is decreased by 57.46% comparison with the IED-EG process.

Hollow and porous TiO2 in PVA matrix nanocomposite green synthesis using ionic liquid micelle for Congo red removal from contaminated water

A new green procedure has been applied to prepare TiO2 nanocomposite in polyvinyl alcohol (PVA) matrix using an aqueous micelle solution of ionic liquid 1-methyl-3-octylimidazolium bromide by determining critical micelle concentration (CMC). The COSMO-SAC model has been used to calculate the activity coefficient of water and understand the water molecules’ behavior in the synthesis mixture. The prepared nanocomposite was porous and layered that has been characterized using FT-IR, XRD, DSC, TGA, SEM, EDX, and elemental mapping. The prepared nanocomposite has been used to remove Congo red dye from contaminated water with the adsorption process. The Langmuir, Freundlich, and Temkin isotherms have been used for modeling equilibrium adsorption of dye removal. Also, the optimized process factors have been evaluated that could achieve 97% dye removal in the following conditions: pH = 12, T = 25 ℃, and t = 45 min using 0.2 g TiO2@PVA (Mesh 100)/L of 10 ppm Congo red aqueous solution. Also, the efficiency of the nanocomposite was 88% after 5 recovery cycles from the optimized condition.

Phase behavior and molecular insights on the separation of dimethyl carbonate and methanol azeotrope by extractive distillation using deep eutectic solvents

Deep eutectic solvents (DESs) exhibit good separation performance as extractants in extractive distillation. In this study, choline chloride (ChCl)-based and tetrabutylammonium bromide (TBAB)-based DESs were prepared using ChCl and TBAB as hydrogen bond acceptors (HBAs) and urea, glycerol (G), malonic acid (MA), and levulinic acid (LA) as hydrogen bond donors (HBDs). Based on the COSMO-SAC model, the possibility of separating the binary azeotropes of methanol (MeOH) and dimethyl carbonate (DMC) using five DESs was verified. The binary azeotropes of MeOH and DMC were separated by extractive distillation using five DESs, and their separation performance was investigated. The experimental results revealed that ChCl-urea had the best separation effect on the binary azeotropes MeOH and DMC. The macroscopic separation phenomenon and microscopic molecular mechanisms were studied systematically. The interaction of the DESs with MeOH and DMC was investigated at the molecular level by quantum chemical (QC) calculations, and the important role of the hydrogen bond of the DESs in extractive distillation was revealed. The experimental and QC results demonstrate that DESs have a significant effect on the intermolecular forces and can effectively separate azeotropes.

Liquid-liquid equilibrium and insights of intermolecular interactions for separation of isopropyl acetate + isopropanol by imidazolium-based ionic liquids

BackgroundDuring the production of isopropyl acetate (IPAC), a mixture of IPAC and isopropanol (IPA) can be produced. Because IPAC and IPA can form a minimum azeotropic mixture with the azeotropic temperature of 354.08 K, it is difficult to separate such a mixture. In this work, liquid-liquid extraction is considered to separate the mixture of IPAC and IPA. Herein, the liquid-liquid equilibrium (LLE) data was determined and correlated for the separation of IPAC and IPA. MethodsFor separating IPAC and IPA by extraction, three ionic liquids (ILs) 1-ethyl-3-methyl-imidazolium hexafluorophosphate, 1‑butyl‑3-methyl-imidazolium hexafluorophosphate and 1‑butyl‑3-methyl-imidazolium dihydrogen phosphate were selected as extractants. The liquid-liquid equilibrium phase behavior of ternary mixtures (IPAC + IPA + ILs) at 298.15 K was investigated. The distribution functions of charge density and interaction energy were determined by the COSMO-SAC model and Dmol3 in Materials Studio, and the interactions between molecules were explored. Significant findingsThe experimental data showed that the three ILs can extract IPA from the mixture of IPAC and IPA and the IL [Bmim][H2PO4] has a better extraction ability compared to the other ILs. The measured LLE data were fitted using the NRTL model and the interaction parameters were regressed, which is a favor in separating the mixture for industrial practice.

Separation of isopropyl alcohol + isopropyl acetate azeotropic mixture: Selection of ionic liquids as entrainers and vapor–liquid equilibrium validation

Based on the COSMO-SAC model, 1-ethyl-3-methylimidazolium acetate and 1-ethyl-3-methylimidazolium p -toluenesulfonate were selected from 30 ILs as entrainers to investigate the separation of the isopropyl alcohol + isopropyl acetate azeotrope. Two screening indicators, σ -profile and infinite dilution selectivity ( S ∞ ), were adopted as the basis. The isobaric vapor–liquid equilibrium experiments for isopropyl alcohol + isopropyl acetate binary system and isopropyl alcohol + isopropyl acetate + confirmed ILs ternary systems were performed at the pressure of atmospheric pressure. The experimental measurement demonstrated that the adopt ILs enhanced the relative volatility of the above alcohol-ester azeotrope, leading to the elimination of the azeotropic point with a certain amount ILs. Meanwhile, the thermodynamic correlation for two systems containing ILs was explored with the NRTL model, which also reflects the extensive applicability of that by comparing the deviation between experimental and calculated data. And its binary interaction parameters were regressed, which can provide a basis for its simulation process.

Economic, environmental, exergy (3E) analysis and multi-objective genetic algorithm optimization of isopropyl acetate production with hybrid reactive-extractive distillation

Isopropyl acetate (IPAC) is an important fine chemical intermediate with a great demand for industrial production. In view of the high energy consumption in the traditional reactive distillation (RD) process of IPAC production, this study further proposed three enhanced processes of reactive-extractive distillation (RED), reactive-extractive dividing wall column (REDWC) and reactive-extractive distillation coupled pervaporation (REDPV) process. Firstly, the surface charge density distribution between components is calculated by COSMO-SAC model to screen a variety of potential solvents. Combined with the empirical screening method, relative volatility is used to determine the optimal solvent. Then, the conceptual design of RD, RED and REDWC three processes are completed based on reaction kinetics, and the operating conditions of processes are optimized by multi-objective genetic algorithm. Furthermore, REDPV process using pervaporation module instead of solvent recovery column is proposed. Finally, the total annual cost (TAC), gas emissions and exergy efficiency are used to evaluate the proposed process. The results show that compared with RD process, the TAC and gas emission of RED process are reduced by 42.69% and 49.82%. While those of REDWC process are reduced by 45.06% and 52.93%. The thermodynamic efficiency of these two processes is increased by 63.28% and 62.67%. Compared with RED process, REDPV process further reduces the cost by 14.45% and the gas emissions by 34.55%, but obtain the lowest thermodynamic efficiency.

Different extractive distillation processes for isopropanol dehydration using low transition temperature mixtures as entrainers

Low transition temperature mixtures (LTTMs) are effective and environmental-friendly entrainers for extractive distillation. However, process intensification for the LTTMs extractive distillation process is less studied. This paper provides a techno-economic study for the separation of isopropanol and water by extractive distillation using ChCl/EG1:2 as entrainer. Firstly, the σ-profiles based on the COSMO-SAC model, the residue curve maps and univolatility lines are used to investigate the advantages of ChCl/EG1:2 over ethylene glycol. Then, the conventional extractive distillation (CED) system with EG or ChCl/EG1:2 entrainers are simulated and optimized by non-dominated sorting genetic algorithm-II (NSGA-II) method with targets of minimum total annual cost (TAC), minimum CO2 emissions and minimum global energy consumption (GEC). The TAC of the CED process using ChCl/EG1:2 as entrainer is reduced by 13.75% than that of the process using ethylene glycol as entrainer. Finally, in order to reduce energy consumption, the processes of extractive dividing wall column (EDWC) and the side-stream extractive distillation system (SED) with ChCl/EG1:2 as entrainer are simulated and optimized. The results show that the EDWC with ChCl/EG1:2 can save 23.83% of TAC, 23.43% of CO2 emissions and 22.66% of GEC compared with the CED process using EG as entrainer.

Removal intensification of basic and non-basic nitrides from liquid fuels by the optimization design of quaternary ammonium salt green solvents

Nitrogen compounds significantly affect the quality of oil products; therefore, the removal of these compounds from oil products has attracted significant attention. In this study, a novel method for separating nitrogen compounds from oil using quaternary ammonium salt (QAS) as an extractant to form deep eutectic solvents (DESs) with non-basic nitrides, interacting with basic nitrides was proposed. Based on the COSMO-SAC model, the possibility of nitrogen compounds acting as hydrogen-bond donors in oil was verified. The effects of four QAS types, agent oil ratios, reaction temperatures, and stirring times on the removal of nitrogen compounds in simulated oil, and the effects of the stripping agent type and recovery times on the recovery rate of QAS were investigated. The DESs were analyzed and characterized by Fourier-transform infrared spectroscopy. The results indicated that tetraethyl ammonium chloride (TEAC) was the best denitrogenation agent. When the stirring time was 8 min, the removal rate of the nitrogen compounds reached 92.62%. Simultaneously, the removal mechanism was studied at the molecular level using a quantum chemical calculation method. Ethyl acetate was used as the stripping agent. After five recovery cycles, the recovery rate of TEAC was 91.5%. This method demonstrates a high selectivity, rapid extraction efficiency, and high recovery efficiency. This study provides theoretical guidance for the efficient and green removal of nitrogen compounds from oil products.

Process evaluation for the separation of acetonitrile-water using extractive distillation with deep eutectic solvents as entrainers

Deep Eutectic Solvents (DESs) show properties that make them effective as environmental-friendly entrainers for extractive distillation. However, the technical and economic evaluation via process simulation and the method of screening a suitable DES for a given azeotropic system are less studied. In this work, the extractive distillation process for acetonitrile dehydration with glycolic acid/choline chloride 3:1 (GC3:1) as entrainer is studied. Firstly, the σ-profiles based on the COSMO-SAC model are employed to select an appropriate DES entrainer. Then, the feasibilities of GC3:1 and ethylene glycol (EG) as entrainer are further studied by the analysis of residue curve maps. Finally, the design and optimization of the extractive distillation process for acetonitrile dehydration with GC3:1 and EG are conducted. The results demonstrate that the conventional extractive distillation process with GC3:1 entrainer gives 13.40% and 9.64% reduction in TAC over the conventional and heat-integrated extractive distillation processes with EG as entrainer, respectively. The TAC of the GC3:1 process is further reduced by 3.14% after heat integration. In addition, the control scheme of the extractive distillation process with GC3:1 entrainer is studied by Aspen Dynamics, and the proposed control structure is effective in managing operational stability.

COSMO-SAC model and vortex assisted liquid-liquid microextraction to assess the hydrophobic deep eutectic solvents as an alternative path for parabens removal from aqueous media

Parabens are widely used preservatives, mainly in personal care products, cosmetics, medicines, and foods. These compounds have been detected in various environmental matrices at low (in the order of µg L−1 or ng L−1) and high concentrations (mg L−1), being recognized as emerging contaminants. In this work, the efficiency of vortex-assisted liquid-liquid microextraction using hydrophobic deep eutectic solvents (HDES) was evaluated in the separation and concentration of parabens (methyl, ethyl, propyl, and butylparaben) in an aqueous solution. The results indicated that the solvents DL-menthol + Caprylic Acid (2:1), DL-menthol + Lactic Acid (1:2), and DL-menthol + Lauric Acid (2:1) are efficient to extract hydrophobic compounds, such as the parabens. The experimental results were supported by the COSMO-SAC predictive thermodynamic model concerning the evaluation of the sigma profile of the molecules. In addition, this model predicts the excess properties of the binaries and explains the behavior of the systems. The potential of liquid-liquid microextraction was demonstrated, given the results presented, and the applicability of the method as an alternative in the removal of micropollutants in aqueous media can be considered.

Modeling of phase separation solvent for CO2 capture using COSMO-SAC model

BackgroundPhase separation solvents are proposed to replace conventional solvents for CO2 capture due to a significant reduction of absorbent regeneration heat. A predictive approach based on COSMO-SAC is developed to model the CO2 capture process using the phase separation solvent of 2-(ethylamino)ethanol (EAE) + water + diethylene glycol diethyl ether (DEGDEE). MethodsIn this approach, liquid phase compositions, including CO2 solubility, are determined from vapor-liquid-liquid equilibrium calculation with a chemisorption reaction in both liquid phases. The behavior of phase separation after CO2 capture and CO2 solubility in both CO2-lean and CO2-rich phases at 313 and 353 K can be well described by the proposed approach. Significant findingsThe overall root-mean-square-deviation (RMSD) in predicting compositions (128 data points) of all components in both liquid phases is 0.064, which is slightly better than a previous study on the accuracy of COSMO-SAC in LLE prediction (RMSD = 0.105). The phase separation behavior of solvent can be realized with the hydrophilic product upon CO2 absorption from the σ-profile analysis. The proposed framework is expected to be a useful tool for the development of a new phase separation solvent.

Catalytic Effect of Ionic Liquid Induced H2-Release from Morpholine Borane Complex: An Efficient Hydrogen Storage Carrier

The demand for effective and secure chemical hydrogen storage systems impedes hydrogen’s usage as an alternative energy carrier. This work reports the use of morpholine borane (MB) as a novel, efficient, and widely viable chemical hydrogen storage material for mobile applications. Herein, for the first time, hydrogen generation from the thermolytic dehydrogenation of MB in the presence of ionic liquid (IL) media is reported. Initially, the COSMO-SAC model was utilized to determine the most appropriate solvent. [Bmim][HSO4] proved to be an excellent catalytic solvent media with maximum solubility in the morpholine borane complex. Thermal dehydrogenation experiments were conducted separately on solid-state and MB-IL systems at 60 and 80 °C in a vacuum-sealed experimental setup. After a prolonged heating period, the solid-state dehydrogenation of the MB complex released 0.62 equiv of hydrogen, whereas the dehydrogenation of the MB-IL system at 60 and 80 °C released 1.75 and 1.46 equiv of hydrogen in a shorter time. The residue products were characterized using 1H and 11B nuclear magnetic resonance (NMR). 1H NMR validated IL’s activity as a catalytic solvent without affecting its structural identity, whereas 11B NMR helped establish an intra- and intermolecular dehydrogenation mechanism connected with MB. As confirmed by the density functional theory-based transition state calculations, the intramolecular dehydrogenation pathway results in a dehydrocoupled product with minimal energy required for the dehydrogenation reaction.

Molecular mechanism, liquid–liquid equilibrium and process design of separating octane-n-butanol system by ionic liquids

The development of clean and green separation technologies has become a key scientific issue in the chemical industry. Because of the wide applicability of ionic liquids (ILs) as green and recyclable extractants, their abilities to extract and separate n-butanol from octane were explored in this work. Based on quantum chemical methods and the COSMO-SAC model, the surface charge density distributions of 22 cations, 19 anions, octane, and n-butanol were calculated. Moreover, the infinite dilution activity coefficients of octane-n-butanol-IL systems were calculated. The distribution coefficients and separation coefficients were also determined. ILs with strong extraction effects (i.e., [Bmim][HSO4], [Bmim][NO3], and [Bmim][OTf]) were used to explore the separation mechanism at the molecular scale; this was conducted by analyzing charge density, bond energy, and bond length of intermolecular interactions. The liquid–liquid equilibrium data of octane-n-butanol-ILs systems were measured, and the distribution coefficients and separation coefficients of each system were calculated. The experimental data were regressed using the NRTL model to obtain the corresponding binary interaction parameters. A process for separating the azeotropic octane and n-butanol systems using ILs was proposed. This process was simulated and optimized using the Aspen Plus 11 software. In addition, the total annual cost was calculated. This work lays the foundation for the screening of green and clean separation solvents.

Phase equilibrium modeling of mixtures containing conformationally flexible molecules with the COSMO-SAC model

The multi-conformational structures sampling of a molecule, considered as conformational information, is found to be crucial for applying COSMO-SAC to systems containing compounds with flexible molecular structures, such as alkylene glycol derivatives. In this study, a hybrid modeling approach that combines the COSMO-SAC model with classical molecular dynamics (MD) is proposed to investigate the phase behavior of systems containing alkylene glycol derivatives. The accuracy in predicting liquid–liquid equilibrium (LLE) was found to be strongly influenced by conformational populations obtaining from MD simulations under different solvation environments. The overall root mean square deviation (RMSD) in predicting LLE mutual solubility from COSMO-SAC for seven selected mixtures containing alkylene glycol derivatives reduces from 19.1% to 10.1% when conformation distribution is included. The new approach significantly improves the accuracy in predicting phase behaviors for alkylene glycol derivatives solutions and can be applied to systems containing compounds with flexible molecular structures.