Modified Separation Of Cohesive Energy Density Research Articles

Correlating Pure Component Properties with MOSCED Solubility Parameters: Enthalpy of Vaporization and Vapor Pressure

Tools to predict vapor–liquid phase equilibria are indispensable for the conceptualization and design of separation processes. Modified separation of cohesive energy density (MOSCED) is a solubility-parameter-based method parameterized to make accurate predictions of the limiting activity coefficient. As a solubility-parameter-based method, MOSCED can not only make quantitative predictions, but can shed light on the underlying intermolecular interactions. In the present study, we demonstrated the ability of MOSCED to correlate the enthalpy of vaporization and vapor pressure at a specific temperature using multiple linear regression. With this addition, MOSCED is able to predict vapor–liquid phase equilibria in the absence of reference data. This was demonstrated for the prediction of the Henry’s constant and solvation free energy of organic solutes in water, which was found to be superior to mod-UNIFAC. In addition to being able to make phase equilibrium predictions, the ability to correlate the enthalpy of vaporization and vapor pressure offers the opportunity to include additional properties in the regression of the MOSCED parameters. Given this success, we additionally attempted to correlate a wide range of physical properties using a similar expression. While, in some cases, the results were reasonable, they were inferior to the correlations of the enthalpy of vaporization and vapor pressure. Future efforts will be needed to improve the correlations.

Prediction of azeotrope formation in binary mixtures with pure component properties and limiting activity coefficients

For a binary mixture without azeotrope, its boiling temperature at quasi-infinite dilution TbQID< Tb,H (the higher boiling temperature of the two components), and TbQID> Tb,L (the lower boiling temperature of the two components). For a binary mixture with minimum boiling azeotrope,TbQID < Tb,L at the neighbourhood of the lower-boiling-temperature component. For a binary mixture with maximum boiling azeotrope, TbQID> Tb,H at the neighbourhood of the higher-boiling-temperature component. The above phenomena are used as predicting criteria for azeotrope formation in this paper. The value of TbQID is calculated by inversely using an existing method proposed to estimate the vaporization heat of pure liquid at its normal boiling temperature. The vaporization heat of the binary mixture at quasi-infinite dilution is taken as the sum of the vaporization heats of the pure components and the mixing heat to form the mixture, where the mixing heat can be estimated with the MOSCED (modified separation of cohesive energy density) Model or other limiting activity coefficient models. The method proposed requires only pure component properties, Tb, Tc, Pc and the MOSCED parameters. The method is illustrated with 311 mixtures, and about 89% of mixtures are predicted successfully.

Predicting the Solubility of Nonelectrolyte Solids Using a Combination of Molecular Simulation with the Solubility Parameter Method MOSCED: Application to the Wastewater Contaminants Monuron, Diuron, Atrazine and Atenolol

Methods to predict the equilibrium solubility of nonelectrolyte solids are indispensable for early-stage process development, design, and feasibility studies. Conventional analytic methods typically require reference data to regress parameters, which may not be available or limited for novel systems. Molecular simulation is a promising alternative, but is computationally intensive. Here, we demonstrate the ability to use a small number of molecular simulation free energy calculations to generate reference data to regress model parameters for the analytical MOSCED (modified separation of cohesive energy density) model. The result is an efficient analytical method to predict the equilibrium solubility of nonelectrolyte solids. The method is demonstrated for the wastewater contaminants monuron, diuron, atrazine and atenolol. Predictions for monuron, diuron and atrazine are in reasonable agreement with MOSCED parameters regressed using experimental solubility data. Predictions for atenolol are inferior, suggesting a potential limitation in the adopted molecular models, or the solvents selected to generate the necessary reference data.

Assessment of the SM12, SM8, and SMD Solvation Models for Predicting Limiting Activity Coefficients at 298.15 K

The SMx (x = 12, 8, or D) universal solvent models are implicit solvent models which using electronic structure calculations can compute solvation free energies at 298.15 K. While solvation free energy is an important thermophysical property, within the thermodynamic modeling of phase equilibrium, limiting (or infinite dilution) activity coefficients are preferred since they may be used to parameterize excess Gibbs free energy models to model phase equilibrium. Conveniently, the two quantities are related. Therefore the present study was performed to assess the ability to use the SMx universal solvent models to predict limiting activity coefficients. Two methods of calculating the limiting activity coefficient where compared: (1) the solvation free energy and self-solvation free energy were both predicted and (2) the self-solvation free energy was computed using readily available vapor pressure data. Overall the first method is preferred as it results in a cancellation of errors, specifically for the case in which water is a solute. The SM12 model was compared to both the Universal Quasichemical Functional-group Activity Coefficients (UNIFAC) and modified separation of cohesive energy density (MOSCED) models. MOSCED was the highest performer, yet had the smallest available compound inventory. UNIFAC and SM12 exhibited comparable performance. Therefore further exploration and research should be conducted into the viability of using the SMx models for phase equilibrium calculations.

Comparison of MOSCED (NRTL) model results with regular correlative and predictive models based on vapor-liquid equilibrium calculations for azeotropic systems

The Modified Separation of Cohesive Energy Density (MOSCED) model is an attractive and accurate engineering tool for process design and modeling. MOSCED is able to make qualitative as well as precise quantitative predictions of principal molecular-level interactions. However, the capability of this model in predicting Vapor-Liquid Equilibrium (VLE) of different azeotropic systems has not yet been fully assessed, when compared with the conventional methods. In this study, the ability of MOSCED model to predict the binary interaction parameters of NRTL model has been evaluated by comparing the obtained isobaric phase diagrams of the experimental sets of data for 11 binary isobaric systems. In order to better evaluate the performance of MOSCED model, the same calculations were performed via correlative (Wilson and NRTL) and predictive (UNIFAC) models. The values of statistical parameters have demonstrated acceptable predictions for the studied systems. Overall, the MOSCED model has provided an Average Absolute Relative Deviation(s) (AARD %) of 0.1978% and 4.3239% for temperature and K-value, respectively; which illustrate excellent performance of this model in spite of no dependence on experimental data, which is a big advantage over other methods.

Expanding the Solubility Parameter Method MOSCED to Pyridinium-, Quinolinium-, Pyrrolidinium-, Piperidinium-, Bicyclic-, Morpholinium-, Ammonium-, Phosphonium-, and Sulfonium-Based Ionic Liquids.

MOSCED (modified separation of cohesive energy density) is a solubility parameter method that offers an improved treatment of association interactions. Solubility parameter methods are well known for their ability to both make quantitative predictions and offer a qualitative description of the underlying molecular-level driving forces, lending themselves to intuitive solvent selection and design. Currently, MOSCED parameters are available for 130 organic solvents, water, and 33 imidazolium-based room temperature ionic liquids (ILs). In this work, we expand MOSCED to cover 66 additional ILs containing the pyridinium, quinolinium, pyrrolidinium, piperidinium, bicyclic, morpholinium, ammonium, phosphonium, and sulfonium cations using 10,052 experimental limiting activity coefficients. The resulting parameters may readily be used to predict the phase behavior in mixtures involving ILs.

MOSCED parameters for 1-n-alkyl-3-methylimidazolium-based ionic liquids: Application to limiting activity coefficients and intuitive entrainer selection for extractive distillation processes

Solubility parameter based methods have long been valuable design tools due to their ability to make both quantitative predictions and to shed insight into the underlying intermolecular interactions. The use of MOSCED (modified separation of cohesive energy density) is particularly attractive due to its advanced treatment of association interactions. Nonetheless, the use of MOSCED is limited due to its relatively small parameter matrix. Here, we work to expand MOSCED to cover room temperature ionic liquids (ILs) by regressing parameters for 33 ILs with the common imidazolium based cation. The ability to use MOSCED for intuitive solvent selection is demonstrated by identifying promising IL entrainer candidates to break an example minimum and maximum boiling binary azeotropic system using extractive distillation.

Predicting Limiting Activity Coefficients and Phase Behavior from Molecular Structure: Expanding MOSCED to Alkanediols Using Group Contribution Methods and Electronic Structure Calculations

The modified separation of cohesive energy density (MOSCED) is a powerful tool for early stage process conceptualization and design. It is capable of making quantitative phase-equilibrium calculations, and more importantly may be used to qualitatively understand the underlying molecular level details of a system for intuitive process design. Unfortunately, its use is limited in that parameters must first be known before predictions may be made. Here we explore the use of group contribution methods (GC-MOSCED) and electronic structure calculations in the solvation model based on density (SMD) and SM8 continuum solvation models to calculate missing parameters. We demonstrate the use of GC-MOSCED to expand MOSCED using limited data, and the ability of electronic structure calculations to calculate parameters devoid of experimental data. While GC-MOSCED performs best, we demonstrate that good predictions may be made using electronic structure calculations with the SMD continuum solvation model. Application is...

Estimation of MOSCED parameters from the COSMO-SAC database

MOSCED (Modified Separation of Cohesive Energy Density) is a particularly attractive model for infinite dilution activity coefficients because it offers intuitive insights into how to tune solvent-solute interactions to achieve optimized formulations. Unfortunately, only 133 compounds have been characterized with the MOSCED method. Available methods for extending MOSCED predictions to new compounds involve quantum mechanical computations on a compound-by-compound basis. On the other hand, surface charge densities (σ-profiles) from density functional theory (DFT) computations are readily available for 1432 compounds through a public database. This work develops correlations for estimating MOSCED parameters from the available σ-profiles, extending the applicability of MOSCED from 133 to roughly 1400 compounds. Additional DFT computations for new compounds would be straightforward.The predictive functions were regressed based on 4368 binary solution infinite dilution activity coefficients. The average logarithmic deviation for the predictive MOSCED model was 0.318 while using the original correlative model had a deviation of 0.106 compared to 0.183 for the UNIFAC model and 0.444 for the Virginia Tech implementation of COSMO-SAC. Analysis of a predictive “simplified” SCED model (PSSCED) was also considered. Omitting MOSCED's polarity and solvent polarity parameters increased deviations to 0.596. As a basis for comparison, regular solution theory provided deviations of 0.947 for the same data set.

Assessment and Revision of the MOSCED Parameters for Water: Application to Limiting Activity Coefficients and Binary Liquid–Liquid Equilibrium

Modified Separation of Cohesive Energy Density (MOSCED) is an attractive method for modeling phase-equilibria because it both can make quantitative predictions and give insight into the system’s underlying molecular-level interactions. While MOSCED predicts satisfactory values of limiting activity coefficients of organics in water, we find that predicted limiting activity coefficients for water (here the solute) in organic solvents shows a much greater disparity with reference data. Moreover, the error is systematic and increases as the value of the limiting activity coefficient increases. After detailed assessment of the MOSCED parameters for water, we find this is not a limitation of the model but results from how the parameters were regressed. As a consequence, in the present study we reregress MOSCED parameters for water which greatly improves the accuracy with which MOSCED may predict limiting activity coefficients of water in organic solvents, with the average absolute error decreasing from 3056.2% to 63.2%. The improvement is systematic, increasing as the value of the limiting activity coefficient increases. We additionally demonstrate the ability of the revised parameters to make improved binary liquid–liquid equilibrium calculations in aqueous systems.

Application of MOSCED To Predict Limiting Activity Coefficients, Hydration Free Energies, Henry’s Constants, Octanol/Water Partition Coefficients, and Isobaric Azeotropic Vapor–Liquid Equilibrium

Modified Separation of Cohesive Energy Density (MOSCED) is a solubility parameter-based method to predict limiting activity coefficients. In addition to making quantitative predictions, MOSCED may additionally be used to understand the underlying molecular-level driving forces for intuitive solvent selection and formulation. A major improvement of MOSCED over similar solubility parameter methods is that it splits the association term. We show by example how this change allows MOSCED to better model the molecular interactions of associating fluids. While parametrized to predict limiting activity coefficients, we demonstrate the ability to predict hydration-free energies, Henry’s constants in water, and octanol/water partition coefficients. We focus on water as MOSCED was previously found to perform substantially worse when water was the solvent. Comparison is made to molecular simulation and mod-UNIFAC, and we find for the studied reference set that predictions with MOSCED were in better agreement with exp...

GC-MOSCED: A group contribution method for predicting MOSCED parameters with application to limiting activity coefficients in water and octanol/water partition coefficients

The MOdified Separation of Cohesive Energy Density (MOSCED) is a solubility parameter based method that can both quantitatively predict limiting activity coefficients and can additionally be used to qualitatively understand the underlying molecular-level interactions for intuitive solvent selection and formulation. However, before predictions may be made, MOSCED parameters must be available. Here we propose a group contribution method (GC-MOSCED) to predict parameters devoid of experimental data. Predictions of limiting activity coefficients in water and octanol/water partition coefficients made using GC-MOSCED are found to be in close agreement with MOSCED using existing parameters. We additionally propose a relation between MOSCED parameters and enthalpy of vaporization, and demonstrate the ability of GC-MOSCED to predict enthalpy of vaporization. An interactive software suite has also been developed to facilitate the calculation of GC-MOSCED parameters.

Predicting the equilibrium solubility of solid polycyclic aromatic hydrocarbons and dibenzothiophene using a combination of MOSCED plus molecular simulation or electronic structure calculations

ABSTRACTMethods to predict the equilibrium solubility of non-electrolyte solids are important for the design of novel separation processes. Here we demonstrate how conventional molecular simulation free energy calculations or electronic structure calculations in a continuum solvent, here SMD or SM8, can be used to predict parameters for the MOdified Separation of Cohesive Energy Density (MOSCED) method. The method is applied to the solutes naphthalene, anthracene, phenanthrene, pyrene and dibenzothiophene, compounds of interested to the petroleum industry and for environmental remediation. Adopting the melting point temperature and enthalpy of fusion of these compounds from experiment, we are able to predict equilibrium solubilities. Comparing to a total of 422 non-aqueous and 193 aqueous experimental solubilities, we find the proposed method is able to well correlate the data. The use of MOSCED is additionally advantageous as it is a solubility parameter-based method useful for intuitive solvent selection and formulation.

Combining MOSCED with molecular simulation free energy calculations or electronic structure calculations to develop an efficient tool for solvent formulation and selection.

Solubility parameter based methods have long been a valuable tool for solvent formulation and selection. Of these methods, the MOdified Separation of Cohesive Energy Density (MOSCED) has recently been shown to correlate well the equilibrium solubility of multifunctional non-electrolyte solids. However, before it can be applied to a novel solute, a limited amount of reference solubility data is required to regress the necessary MOSCED parameters. Here we demonstrate for the solutes methylparaben, ethylparaben, propylparaben, butylparaben, lidocaine and ephedrine how conventional molecular simulation free energy calculations or electronic structure calculations in a continuum solvent, here the SMD or SM8 solvation model, can instead be used to generate the necessary reference data, resulting in a predictive flavor of MOSCED. Adopting the melting point temperature and enthalpy of fusion of these compounds from experiment, we are able to predict equilibrium solubilities. We find the method is able to well correlate the (mole fraction) equilibrium solubility in non-aqueous solvents over four orders of magnitude with good quantitative agreement.

Infinite-dilution activity coefficients by comparative ebulliometry. Binary systems containing chloroform and diethylamine

Coutinho, J.P., and Macedo, E.A., 1994. Infinite-dilution activity coefficients by comparative ebulliometry. Binary systems containing chloroform and diethylamine. Fluid Phase Equilibria, 95: 149-162. New data were determined by comparative ebulliometry for infinite-dilution activity coefficients of the following systems: chloroform/methanol, chloroform/acetonitrile, chloroform/ tetrahydrofuran, chloroform/methyl acetate, chloroform/diethylamine and diethylamine/ n-hexane, at both the upper and lower concentration limits and at two different temperatures. The measured infinite-dilution activity coefficients were compared with the predicted values obtained with the MOSCED (Modified Separation of Cohesive Energy Density) and UNIFAC models. For the UNIFAC model the predictions were made using group-interactions from the VLE parameter Tables. The differences between experimental and calculated infinite-dilution activity coefficients show that both methods predict fairly well the majority of the experimental data. The data obtained were used to estimate UNIFAC interaction parameters for the groups CCl3/CH3OH, CCl3/CCN, CCl3/CH2O, CCl3/CCOO, CCl3/CNH and CH2/CNH, which are not available in the infinite-dilution specific Parameter Table. These parameters were used to predict VLE data for systems containing the same groups, and a comparison between experimental and predicted values is presented.