COSMO-SAC Model Research Articles

Mechanism analysis of extractive distillation for separation of acetic acid and water based on quantum chemical calculation and molecular dynamics simulation

The selection of high efficiency and environmental protection entrainer is the inevitable requirement of extractive distillation sustainable development. According to the extraction mechanism, the σ-profile was drawn by COSMO-SAC model. Based on the quantum chemistry method, the interaction energy, deformation charge density and total charge density of different organic solvent, ionic liquids and acetic acid-water system were calculated. The binding energy between organic solvents, ionic liquids and acetic acid-water system was further analyzed by Gaussian software. The binding energies of organic solvent tetramethylene sulfone and 1-butyl-3-methylimidazolium dibutyl phosphate ([BMIM][BDP]) ionic liquid with acetic acid were - 934.9622 a.u., − 1610.6557 a.u., respectively. Through molecular dynamics simulation, the radial distribution functions of organic solvents and ionic liquids were calculated and compared at the molecular level, and the interaction between different molecules was analyzed. The cation plays a leading role. When Å = 4.5, ionic liquid and solvent interact strongly with acetic acid, respectively. The comprehensive results showed that tetramethylene sulfone and [BMIM][BDP] had better extraction effect. Finally, the self-diffusion coefficient of [BMIM][BDP] and HAc is 0.0105 cm2 / s. The combination of quantum chemical calculation and molecular dynamics simulation provides theoretical guidance for the effective separation of acetic acid-water system, which provides a certain reference for the selection of the best entrainer.

Separation of n-heptane and tert-butanol by ionic liquids based on COSMO-SAC model

In the process of liquid–liquid extraction, it is necessary to look for green solvents as extractants. Ionic liquids have been studied as extractants due to their green recyclability in recent years. The infinite dilution activity coefficients of 100 ionic liquids with a combination of 10 cations and 10 anions were calculated by COSMO-SAC model, and the σ-profiles were plotted. The distribution coefficient and separation coefficient of n-heptane + tert-butanol + ILs were determined. [OMIM][OTF], [HMIM][OTF] and [BMIM][OTF] were selected as solvents for this study. The interaction energy, bond length and charge density of ionic liquids with tert-butanol were calculated by quantum chemistry calculation method. According to these results, the rationality of selected ionic liquids as extractants could be analyzed from the molecular level. At 298.15 K and 101.325 kPa, the liquid–liquid equilibrium data of the ternary system {n-heptane + tert-butanol + [OMIM][OTF], n-heptane + tert-butanol + [BMIM][OTF], n-heptane + tert-butanol + [HMIM][OTF]}) were measured. The distribution coefficient and separation coefficient for judging the extraction effect were obtained. The NRTL model was used to correlate liquid–liquid equilibrium experimental data, and correlation result proved that the correlated and experimental data had a good correlation. The research on ionic liquids is of great significance to the development of green and sustainable chemical industry.

Role of Computational Variables on the Performances of COSMO-SAC Model: A Combined Theoretical and Experimental Investigation

The effect of key computational parameters of the quantum chemical approach underpinning the COSMO-SAC model is investigated, considering as target property the activity coefficients at infinite dilution, γ∞, of furan in several solvents. In particular, different density functional theory models, as well as parameters concerning the solvent model (COSMO), are varied, and the obtained results were compared with the experimental data, integrated with specific experiments, as well as with those provided by empirical methods such as UNIFAC. The results show that a significant improvement in the COSMO-SAC evaluation of γ∞ is obtained by a judicious choice of the computational parameters, including the exchange–correlational functionals and the atomic cavity radii. More importantly, the accuracy of the obtained protocol on γ∞ is significantly better than that provided by the robust and widely used UNIFAC model.

Separation of low molecular weight alcohols from water with deep eutectic solvents: Liquid-liquid equilibria and process simulations

Low molecular weight alcohols such as ethanol, propanol and butanol are currently gaining attention owing to their complete combustion and higher calorific value. These low molecular weight alcohols are obtained by ABE (acetone−butanol−ethanol) fermentation, where they are produced within an aqueous phase. Extraction is contemplated as one of the effective methods for the separation of these lower alcohols from aqueous phase through a solvent. The solvent explored here relates to the formulation of Deep Eutectic Solvent (DES) comprising of DL-menthol (Hydrogen Bond Donor) + decanoic acid (Hydrogen Bond Acceptor). The current work adopts a multiscale approach leading with DES preparation and subsequent batch scale Liquid-Liquid Equilibria (LLE) measurement and finally concludes through process simulation studies. The experimental LLE data of DES (1)-Alcohol (2)-Water (3) gave a higher affinity towards alcohol and lower solubility with water. The experimental results were thereafter regressed with the NRTL model using the additional constraint where a positive tangent plane distance is imposed for all the tie lines within the Gibbs energy of mixing (Gm) surface. The average absolute RMSD values correlated via NRTL and COSMO-SAC model were found to be 0.003 and 0.008 respectively. A flow sheet with a hybrid extraction-distillation system is then proposed and simulated for the solvent recovery, scale-up and cost analysis.

Investigation of COSMO-SAC model for solubility and cocrystal formation of pharmaceutical compounds

In this study, a predictive model named COSMO-SAC was investigated in solid/liquid equilibria for pharmaceutical compounds. The examined properties were the solubility of drug in the pure and mixed solvents, octanol/water partition coefficient, and cocrystal formation. The results of the original COSMO-SAC model (COSMO-SAC (2002)) was compared with a semi-predictive model named Flory–Huggins model and a revised version of the COSMO-SAC (COSMO-SAC (2010)). The results indicated the acceptable accuracy of the COSMO-SAC (2002) in the considered scope. The results emphasized on the suitability of the COSMO-SAC model for simple molecules containing C, H, and O by covalent and hydrogen bonding interactions. Applicability of the COSMO-SAC for more complicated molecules made of various functional groups such as COO and COOH doubly requires more modification in the COSMO-SAC.

Predictions of thermodynamic properties and phase equilibria of refrigerant systems with COSMO approaches

The knowledge of the phase equilibrium of refrigerant mixtures is crucial for the optimization of the production processes of refrigerant molecules, and the design of energetic systems (heat pumps, Organic Rankine Cycles, …). In this work, different predictive thermodynamic models (COSMO-RS and COSMO-SAC-dsp) have been used to determine the phase behavior of mixtures of refrigerants involving alkanes, fluorinated and chlorinated compounds. The COSMO-RS model leads to rather satisfactory predictions of the vapor-liquid equilibria of mixtures and is able to capture the azeotropic behavior for most systems. However, the original COSMO-SAC model as well as the COSMO-SAC 2010 version lead to unsatisfactory predictions of VLE for these systems, as they are unable to predict the azeotropic behavior in alkane + refrigerants. By combining COSMO-SAC with a dispersion term (COSMO-SAC dsp model) and readjusting the universal parameter for the F atom, it is possible to get very satisfactory predictions of similar accuracy as COSMO-RS. In order to predict the phase behavior at high pressure, the COSMO-SAC-dsp model can be combined with the Peng-Robinson equation of state and the MHV1 mixing rule. Excellent predictions of relative volatilities can be obtained with this approach over wide temperature and pressure ranges. COSMO calculation can also be used to predict saturated liquid densities, vaporization enthalpy and boiling points of pure refrigerants.

Sustainable wastewater treatment via PV-distillation hybrid process for the separation of ethyl acetate/isopropanol/water

The recovery of ethyl acetate and isopropanol from ampicillin sodium wastewater is an important task. The existence of azeotropes system makes it difficult to achieve high purity separation by conventional distillation. In this work, the extractive distillation of ethyl acetate/isopropanol/water by efficient separation method was explored. Based on the COSMO-SAC model, the infinite dilution activity coefficients of the components were calculated, and the potential extractant was further determined. Taking the minimum TAC as the objective function, a sequential iterative method was used to optimize the process. Furthermore, steam recompression and pervaporation technologies were used to reduce the process energy consumption. The economic and environmental performance of several processes was calculated to assess their feasibility. It is conclusion that compare with basic process, the steam recompression process performs well in both economy and environment. While the pervaporation-distillation hybrid process obtained a better environmental performance but showed poor economic performance due to huge equipment costs, which requires a corresponding tradeoff based on the actual industry.

Energy-saving investigation of organic material recovery from wastewater via thermal coupling extractive distillation combined with heat pump based on thermoeconomic and environmental analysis

Cyclohexane and sec-butyl alcohol are widely used in the pharmaceutical and chemical industries. The separation of cyclohexane/sec-butyl alcohol/water azeotropic mixture is of great significance for mitigating environmental risk, recycling solvents, and maintaining developmental sustainability. Based on the COSMO-SAC model, the infinite dilution activity coefficients of the components were calculated, and the final solvent was further obtained by relative volatility and solvent power screening. Taking the total annual cost as the objective function, the extractive distillation process is optimized based on a sequential iterative optimization algorithm. To further reduce the process energy consumption, several energy-saving processes were explored. Energy-saving processes are compared in terms of total annual cost, CO2 emissions, and thermodynamic efficiency. It was found that the total annual cost and thermodynamic efficiency of the processes show an increasing trend, while CO2 emissions show a decreasing trend. The results of stage-exergy indicate that the processes with heat pump are relatively small. The heat pump combined with the thermal coupling extractive distillation process exhibits better thermoeconomic and environmental performance. It provides theoretical guidance for improving the separation and recovery of value organics and energy-saving optimization of processes, which conforms to the theme of sustainable and environmental development.

Extraction of ethanol from mixtures with n-hexane by deep eutectic solvents of choline chloride + levulinic acid, + ethylene glycol, or + malonic acid

The separation of azeotropic mixtures is a great challenge for concentrating a desired chemical compound because it cannot be attained by a simple distillation process. Liquid-liquid extraction can be an alternative process to resolve the separation problem if an appropriate solvent is selected to effectively partition the mixture. In this work, the feasibilities of three different deep eutectic solvents (DESs) for breaking azeotropes of n-hexane and ethanol mixture were examined by means of liquid-liquid extraction. Choline chloride (ChCl) was chosen as a base compound and three hydrogen bond donors (HBDs) of levulinic acid, ethylene glycol, and malonic acid were added at their eutectic ratio to form DESs. Liquid-liquid equilibrium experiments for an azeotropic n-hexane + ethanol system were carried out to determine binodal compositions and, then, evaluate the compositions at both liquid phases at 298.2 K and atmospheric pressure by employing the prepared DESs. Refractive index, density, and viscosity at the binodal compositions were measured to provide properties required for extraction process establishment. The measured tie-lines were compared with the predicted results calculated by COSMO-SAC model. Moreover, the ability for extracting ethanol was evaluated with distribution coefficient and selectivity. It was found that the distribution coefficient and selectivity values are high enough to support a scaling-up process by a liquid–liquid extraction.

Quantum chemical calculation, molecular dynamics simulation and process design for separation of heptane - butanol using ionic liquids extraction

Investigating energy-saving and environmentally friendly green solvents is an inevitable requirement for the sustainable development of liquid-liquid extraction. In this work, σ- profiles were drawn using COSMO-SAC model according to the extraction mechanism. Based on quantum chemistry method, the interaction energy, total charge density, deformed charge density and bond length of ionic liquids and butanol were calculated. According to the absolute value of the interaction energy, the hydrogen bond of the total charge density and the deformed charge density, the extractant with good extraction effect can be determined. The radial distribution function of ionic liquids was calculated at the molecular level through molecular dynamics simulation, and the extraction ability of ionic liquids were analyzed. According to the binary interaction parameters obtained from the liquid-liquid equilibrium data of 298.15 K ternary system, the extraction process was simulated. The minimum total annual cost was calculated when the required butanol recovery and heptane purity were achieved. Combining quantum chemical calculation and molecular dynamics simulation to select the best extractant, and verifying the feasibility of ionic liquids as extractant through the simulation process, is of great significance for the industrial application of ionic liquids.

An extended COSMO-SAC method for the prediction of carboxylic acid solubility

The COSMO-SAC model provides a convenient method for predicting the phase behavior of components with minimal information about molecules using quantum-mechanical principles. During the past few years, several researchers tried to improve the prediction capability with modifications to hydrogen bonding terms and other methods of calculation. In this contribution, we focused on carboxylic acid groups, which may exhibit different hydrogen-bond behavior as compared with alcohols. The calculation scheme in COSMO-SAC (2017 version) was slightly modified to encompass a hydrogen-bond term specifc to carboxylic acid groups. The parameters for the extended COSMO-SAC model were fitted using 559 data points. The characteristics of the extended model were investigated for the prediction capability of binary solubility, ternary solubility, and vapor-liquid equilibrium data. The results show that the extension correctly predicts the phase behavior of mixtures containing carboxylic acids.

Rigorous simulation and techno-economic analysis of a bio-jet-fuel intermediate production process with various integration strategies

In this paper, we firstly report on the different scenarios of the process integration to produce jet-fuel intermediates from biomass. Rigorous process simulation, optimization, techno-economical evaluation, and carbon emission calculation are performed. We start from the aldol condensation process converting furfural and acetone to the jet-fuel intermediate. COSMO-SAC model and the PR+COSMOSAC equation of state (EOS) are firstly incorporated to estimate the missing physical properties of both pure component and the mixture. In this part, three process schemes (the distillation-only process, the multi-effect evaporation (MEE) assisted process, and the solvent-less process) are investigated, and the total annual cost (TAC) are compared. Comparing with the distillation-only process, the optimization results indicate a more favorable condition in the solvent-less process (89.76% TAC reduction) than the MEE-assisted process (25.54% TAC reduction). Moreover, different strategies of integrating the aldol condensation process with the front-end furfural production process are discussed. They are presented in five scenarios. YUMC (yearly unit manufacture cost) and ER (emission ratio) are calculated to quantify the economic performance and CO2 emission. Through this work, we suggest that the Scenario 4 (YUMC=0.716USD/kg, ER=−1.65) would be the most suitable one for CO2 reduction in the future, and the Scenario 2 (YUMC=0.698USD/kg, ER=0.28) could be the nearest solution to enhance the economic performance and reducing CO2 emission based on the current technology.

Efficient extraction of phenol from low-temperature coal tar model oil via imidazolium-based ionic liquid and mechanism analysis

Abstract Since phenol is a high value-added compound in chemical industry, which is separated from coal tar, in this work, the imidazolium-based ionic liquid, 1-ethyl-3-methyl imidazolium lactate ([EMIM][LAC]) was prepared as extractant to separate phenol from the model oil. The prepared [EMIM][LAC] was characterized by 1H NMR. The effects of extraction temperature, time, and IL/model oil mass ratio were explored. The results showed that [EMIM][LAC] can extract phenol efficiently. Then, the separation mechanism between phenol and [EMIM][LAC] was investigated by discussing the surface-charge density distribution obtained by the COSMO-SAC model and intermolecular interaction obtained by quantum chemical calculations. The results showed that [EMIM][LAC] was a suitable extractant due to hydrogen bond formed by the IL and phenol. Moreover, the chemical bond for [EMIM][LAC] with phenol was further validated by FT-IR spectra.

Improved Prediction of Phase Behaviors of Ionic Liquid Solutions with the Consideration of Directional Hydrogen Bonding Interactions

The consideration of directional hydrogen bonding in the COSMO-SAC model based on the minima in the molecular electrostatic potential has been shown to significantly improve the description of solv...

Predicting phase equilibrium of aqueous sugar solutions and industrial juices using COSMO-SAC

COSMO-SAC model was used to predict bubble point pressure, bubble point temperature, water activity, freezing point depression and solubility of sugars in aqueous solutions. COSMO-SAC is based on quantum chemistry computations and has a high predictive character, not requiring a specific parameter calibration for each application. For most systems studied, the results obtained were close to experimental data, with relative mean errors varying from 0.1% to 6.4% for vapor–liquid equilibrium. Solubility results with COSMO-SAC presented the same tendency observed in experimental data, but with higher deviations, probably due to the fact that the loss of crystalline structure in sugars is a kinetic process more than a thermodynamic melting, and does not occur at a single temperature with a constant enthalpy value. COSMO-SAC model was also used to predict industrial juices water activity, bubble point temperature, and freezing point depression. Very low deviations from experimental data were observed for COSMO-SAC calculations, similar to those found for simpler sugar solutions.

The UNIFAC-LLE and COSMO-SAC ternary aqueous LLE calculations

The reliable description of a liquid-liquid equilibrium system is irrefragably important, given that liquid-liquid equilibrium has several important applications in industry, such as the extraction of propionic acid, reactant of esterification reaction for thermoplastics production, the removal of congeners of bioethanol through the equilibrium displacement by adding water, and the proper calculation of fuel blends equilibrium composition. The use of accurate models is one of the main necessities to achieve good predictions of a system. In this work, the use of the UNIFAC(LLE) and COSMO-SAC (2002) excess Gibbs energy models in liquid-liquid equilibrium is analyzed. Liquid-liquid equilibrium predictions of 55 ternary aqueous systems are performed, the models are compared and their accuracy evaluated. The systems may contain water, alkanes, alkenes, aromatic compounds, acids, alcohols and esters. The COSMO-SAC model yielded the most reliable results, although some systems were better described by the UNIFAC-LLE model.

Experimental measurement, correlation and COSMO-SAC prediction of liquid-liquid equilibrium for MIPK + dimethylphenols + water mixtures

Liquid-liquid equilibrium (LLE) data for ternary systems of methyl isopropyl ketone (MIPK) + 2,3-/3,4-/3,5-dimethylphenol + water was determined from 298.15 K to 338.15 K under 101.3 kPa in this work. Distribution coefficient and selectivity were calculated to investigate solvent extraction efficiency of dimethylphenol from water and their high values indicated that MIPK could extract dimethylphenols well. The NRTL and UNIQUAC models were applied to correlate experimental LLE data and related root-mean square deviations (RMSDs) were less than 0.5%. Additionally, the experimental data was predicted by COSMO-SAC model, and the corresponding RMSD values demonstrated that COSMO-SAC model can be applied as a predictive tool to calculate LLE data of the investigated ternary systems.

Separation of azeotrope 2,2,3,3-tetrafluoro-1-propanol and water by extractive distillation using ionic liquids: Vapor-liquid equilibrium measurements and interaction analysis

To separate the azeotrope 2,2,3,3-tetrafluoro-1-propanol (TFP) and water, the extractive distillation was applied using ionic liquids. In this work, two ionic liquids, [EMIM][Ac] and [EMIM][Cl], were selected as the entrainers screened by the COSMO-SAC model. For purpose of validating the separation effect of these two ionic liquids, the isobaric vapor-liquid equilibrium (VLE) data for the mixtures (water + TFP + [EMIM][Ac] / [EMIM][Cl]) were determined at 101.3 kPa with a modified Rose-type recirculating still. By adding certain amount of entrainers, the relative volatility increased significantly. Afterwards, the NRTL model was adopted to correlate the measured experimental data. Moreover, the surface-charge density distribution (σ-profile) and the interaction energy for the above systems were calculated and explored, which can provide the theoretical insight into the separation of the azeotrope by ionic liquids.

Separation of azeotropic mixture (2, 2, 3, 3-Tetrafluoro-1-propanol + water) by extractive distillation: Entrainers selection and vapour-liquid equilibrium measurements

For separating the azeotrope of 2, 2, 3, 3-tetrafluoro-1-propanol (TFP) and water by extractive distillation, N-methyl pyrrolidone (NMP), N-methyl formamide (NMF) and N, N-dimethyl formamide (DMF) were selected as entrainers using the COSMO-SAC model based on solvent capacity. And the charge density surface of entrainers and each component in the azeotrope system were calculated. The vapour-liquid equilibrium (VLE) data for the mixtures (TFP + NMP), (TFP + NMF) and (TFP + DMF) were measured by a modified Rose-type recirculating still at the pressure 101.3 kPa. The thermodynamic consistency for the VLE data was validated using the Herington and van Ness methods. The VLE data were correlated with NRTL, Wilson and UNIQUAC models, and the interaction parameters of thermodynamic models were fitted. Meanwhile, the effect of the entrainers on the VLE for TFP and water was explored. Compared with NMF and DMF, NMP was adopted as the suitable entrainer for separation of the azeotropic mixture TFP and water by extractive distillation.

Liquid-liquid extraction of methanol from its mixtures with hexane using three imidazolium-based ionic liquids

N-hexane plays a significant role in the industrial manufacturing process of methanol. The separation of n-hexane and methanol is important and difficult due to the azeotropic phenomenon. The objective of this work is to measure the experimental data for the three ternary systems n-hexane + methanol + ionic liquids (1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl), 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide and 1-butyl-3-methylimidazolium hexafluorophosphate) at T = 298.15 K and 101.3 kPa. The COSMO-SAC model was used to calculate the infinite dilution activity coefficients of the eleven ILs in the work and in the literature. The liquid-liquid equilibrium data for the ternary systems were compared with the calculated values obtained using the non-random two liquid and universal quasi-chemical activity models, and the binary interaction parameters of the two models were obtained by regressing the experimental data. Comparing the values of the distribution coefficients and separation factors of the three ILs, 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide showed the best extraction effect. The influence of the alkyl chain length and different anions on the liquid-liquid equilibrium data was discussed.