Original UNIFAC Research Articles

Solubility Prediction of Active Pharmaceutical Compounds with the UNIFAC Model

The crystallization from solution of an active pharmaceutical ingredient requires the knowledge of the solubility in the entire temperature range investigated during the process. However, during the development of a new active ingredient, these data are missing. Its experimental determination is possible, but tedious. UNIFAC Group contribution method Fredenslund et al. (Vapor–liquid equilibria using UNIFAC: a group contribution method, 1977; AIChE J 21:1086, 1975) can be used to predict this physical property. Several modifications on this model have been proposed since its development in 1977, modified UNIFAC of Dortmund Weidlich et al. (Ind Eng Chem Res 26:1372, 1987), Gmehling et al. (Ind Eng Chem Res 32:178, 1993), Pharma-modified UNIFAC Diedrichs et al. (Evaluation und Erweiterung thermodynamischer Modelle zur Vorhersage von Wirkstoffloslichkeiten, PhD Thesis, 2010), KT-UNIFAC Kang et al. (Ind Eng Chem Res 41:3260, 2002), \(\ldots \) In this study, we used UNIFAC model by considering the linear temperature dependence of interaction parameters as in Pharma-modified UNIFAC and structural groups as defined by KT-UNIFAC first-order model. More than 100 binary datasets were involved in the estimation of interaction parameters. These new parameters were then used to calculate activity coefficient and solubility of some molecules in various solvents at different temperatures. The model gives better results than those from the original UNIFAC and shows good agreement between the experimental solubility and the calculated one.

Reparameterization of COSMO-SAC for Phase Equilibrium Properties Based on Critically Evaluated Data

COSMO-SAC model was reparameterized with use of the critically evaluated data generated by the NIST ThermoData Engine for vapor–liquid equilibria, excess enthalpies for binary mixtures, and activity coefficients of binary mixture components. The calculated σ-profile library contained 897 individual compounds. The temperature-dependent σ profiles included contributions of up to 40 conformers of a molecule. Splitting of the H-bonding σ profiles into OH and non-OH parts decreased the root-mean square deviation from the experimental data points by about 10% compared to the model using one H-bonding parameter. The original UNIFAC model demonstrated comparable performance with the more advanced COSMO-SAC variation. The challenges of uncertainty evaluation for parameters of the model and the predicted values are discussed.

Phase equilibria of three binary systems containing 2,5-dimethylthiophene and 2-ethylthiophene in hydrocarbons

Isobaric vapor–liquid equilibrium (VLE) data for binary systems 2-ethylthiophene + n-decane, 2,5-dimethylthiophene + n-decane and 2-ethylthiophene + mesitylene were measured at 101.33 kPa using the modified Rose–Williams equilibrium still. Gas chromatography was used to analyze compositions of the samples from the vapor–liquid equilibrium system. Thermodynamic consistency of the experimental data were checked both with the Herington consistency test and point-to-point test of Van Ness, which ensure the reliability of experimental data. The experimental data were correlated by the Wilson and non-random two-liquid (NRTL) activity coefficient models and were compared with original UNIFAC predictive model. The corresponding parameters for the Wilson and NRTL models were obtained. The results show that the calculated values of the vapor-phase mole fraction and bubble point temperature by Wilson, NRTL and UNIFAC models agree well with the experimental data.

Vapour liquid equilibria of monocaprylin plus palmitic acid or methyl stearate at P = (1.20 and 2.50) kPa by using DSC technique

The Differential Scanning Calorimetry (DSC) technique is used for measuring isobaric (vapour+liquid) equilibria for two binary mixtures: {monocaprylin+palmitic acid (system 1) or methyl stearate (system 2)} at two different pressures P=(1.20 and 2.50)kPa. The obtained PTx data are correlated by Wilson, NRTL and UNIQUAC models. The original UNIFAC group contribution method is also considered and new binary interaction parameters for the main groups CH2, CCOO, OH and COOH are regressed, to account for the non-idealities found in these lipid systems. Established thermodynamic consistency tests are applied and attest the quality of the measured data. In terms of relevance of the selected components, system 1 can be found in the purification and deodorization steps during the production of edible oils, while, system 2 can be found in the purification steps of biodiesel. It should be noted that no such data could be found in the open literature, not only for the specific components selected but also for the combination of the classes of components considered; that is, acylglycerol plus fatty acid or fatty ester.

Data, analysis and modeling of physical properties for process design of systems involving lipids

Pure component and mixture properties are necessary for synthesis, design, and analysis of processes for the production of edible oils, fats, biodiesel, and other lipids. The lack of measured data for these systems makes it necessary to develop reliable predictive models based on limited data. We have systematically collected data for vapor–liquid equilibrium (VLE), solid–liquid equilibrium (SLE) and related pure component properties involving lipid systems as a first step toward developing relevant property models. The established consistency tests to evaluate the VLE data of lipid systems as well as lipid properties are briefly reviewed. For SLE systems, where consistency tests based on the Gibbs–Duhem equation cannot be implemented, a consistency test has been developed. It involves limiting conditions and regression of the parameters for a new thermodynamic model that combines solute activity coefficients in the liquid phase at infinite dilution and a theoretically based term to account for the non-ideality in dilute solutions. This model gives noticeably better descriptions of experimental data in lipid systems than do traditional models. Examination of various objective functions for regressing model parameters showed that some variation of parameter values and differences in accuracy can be found, though they are not large. Some original UNIFAC group contribution parameters for lipids have been revised by fitting to the lipid database.

Measurements of activity coefficients at infinite dilution in vegetable oils and capric acid using the dilutor technique

This paper reports experimental activity coefficients at infinite dilution, γi∞, for methanol, ethanol and n-hexane in three refined vegetable oils (soybean, sunflower, and rapeseed oils) measured using the dilutor technique (inert gas stripping method). The measurements were carried out in the temperature range between 313.15 and 353.15K. Furthermore, activity coefficients at infinite dilution for various solutes (acetone, methanol, ethanol, n-hexane, cyclohexane and toluene) were measured in capric (decanoic) acid using the same technique in the temperature range from 313.13 to 353.30K. The new data obtained for capric acid and soybean oil were compared with already published experimental data. Additionally, densities of the investigated vegetable oils were measured in the temperature range from 293.15 to 353.15K. Using the experimental γi∞ values obtained over the temperature range, the partial molar excess Gibbs energy (ΔGiE,∞), enthalpy (ΔHiE,∞) and entropy (ΔSiE,∞) at infinite dilution were determined. The relative error for the γi∞ measurements carried out using the dilutor technique is approximately ±2.5%. The measured γi∞ data in the investigated refined vegetable oils were also compared with the results of the group contribution methods original UNIFAC and modified UNIFAC (Dortmund) and an extension of the latter method to triacylglycerols was proposed.

Correction to “Comparison of the a Priori COSMO-RS Models and Group Contribution Methods: Original UNIFAC, Modified UNIFAC(Do), and Modified UNIFAC(Do) Consortium”

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionORIGINAL ARTICLEThis notice is a correctionCorrection to “Comparison of the a Priori COSMO-RS Models and Group Contribution Methods: Original UNIFAC, Modified UNIFAC(Do), and Modified UNIFAC(Do) Consortium”Zhimin Xue†, Tiancheng Mu†*, and Jürgen Gmehling‡*View Author Information† Department of Chemistry, Renmin University of China, 100872, Beijing, China‡ Department of Industrial Chemistry, Institute for Pure and Applied Chemistry, Carl von Ossietzky Universität Oldenburg, D-26111, Oldenburg, Germany*E-mail: [email protected] (T.M.), [email protected] (J.G.).Cite this: Ind. Eng. Chem. Res. 2012, 51, 49, 16163Publication Date (Web):December 3, 2012Publication History Published online3 December 2012Published inissue 12 December 2012https://doi.org/10.1021/ie303175rCopyright © 2012 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views503Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (121 KB) Get e-Alerts Get e-Alerts

Comment on “Comparison of the a Priori COSMO-RS Models and Group Contribution Methods: Original UNIFAC, Modified UNIFAC(Do), and Modified UNIFAC(Do) Consortium”

ADVERTISEMENT RETURN TO ISSUEPREVCorrespondenceNEXTComment on “Comparison of the a Priori COSMO-RS Models and Group Contribution Methods: Original UNIFAC, Modified UNIFAC(Do), and Modified UNIFAC(Do) Consortium”Andreas Klamt*†‡View Author Information† COSMOlogic GmbH and Co. KG, Burscheider Str. 515, 51381 Leverkusen, Germany‡ Institute of Physical and Theoretical Chemistry, University of Regensburg, 93053 Regensburg, Germany*E-mail: [email protected]Cite this: Ind. Eng. Chem. Res. 2012, 51, 41, 13538–13540Publication Date (Web):October 8, 2012Publication History Published online8 October 2012Published inissue 17 October 2012https://doi.org/10.1021/ie302247qCopyright © 2012 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views558Altmetric-Citations4LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-AlertsSUBJECTS:Activity coefficient,Biological databases,Mixtures,Theoretical and computational chemistry Get e-Alerts

Comparison of the a Priori COSMO-RS Models and Group Contribution Methods: Original UNIFAC, Modified UNIFAC(Do), and Modified UNIFAC(Do) Consortium

A comparison of the performances of the COSMO-SAC, COSMO-RS(Ol), original UNIFAC, modified UNIFAC(Do), and modified UNIFAC(Do) Consortium for activity coefficients at infinite dilution and binary VLE data is presented. The σ-profiles used in performing COSMO-SAC and COSMO-RS(Ol) calculations were taken from the published σ-profile database VT 2005. The predicted results were compared with the experimental data stored in the Dortmund Data Bank and analyzed with respect to the types of components in the mixture. The results show that the UNIFAC models based on experimental data are superior to the a priori COSMO-RS models.

Isobaric vapor–liquid equilibrium for four binary systems of 3-methylthiophene

Isobaric vapor–liquid equilibrium (VLE) data for the systems of 3-methylthiophene with four compounds (2,3-dimethyl-2-butene, n-heptane, toluene and 2-methylbutane) were measured at 101.33kPa with a modified Rose-Williams still. Gas chromatography was used to analyze compositions of the samples from the vapor–liquid equilibrium systems. All the VLE measurements passed the thermodynamic consistency test proposed by Herington and showed positive deviations from Raoult's law. The experimental data of binary systems were correlated by Wilson model for the liquid phase and also compared with original UNIFAC and UNIFAC-Dortmund predictive models. Results showed that the original UNIFAC model gave better predictions than the UNIFAC-Dortmund model.

ThermoData Engine (TDE) Software Implementation of the Dynamic Data Evaluation Concept. 7. Ternary Mixtures

ThermoData Engine (TDE) is the first full-scale software implementation of the dynamic data evaluation concept, as reported in this journal. The present paper describes the first application of this concept to the evaluation of thermophysical properties for ternary chemical systems. The method involves construction of Redlich-Kister type equations for individual properties (excess volume, thermal conductivity, viscosity, surface tension, and excess enthalpy) and activity coefficient models for phase equilibrium properties (vapor-liquid and liquid-liquid equilibrium). Constructed ternary models are based on those for the three pure component and three binary subsystems evaluated on demand through the TDE software algorithms. All models are described in detail, and extensions to the class structure of the program are provided. Reliable evaluation of properties for the binary subsystems is essential for successful property evaluations for ternary systems, and algorithms are described to aid appropriate parameter selection and fitting for the implemented activity coefficient models (NRTL, Wilson, Van Laar, Redlich-Kister, and UNIQUAC). Two activity coefficient models based on group contributions (original UNIFAC and NIST-KT-UNIFAC) are also implemented. Novel features of the user interface are shown, and directions for future enhancements are outlined.

Isobaric vapor–liquid equilibrium for four binary systems of thiophene

Isobaric vapor–liquid equilibrium (VLE) data for thiophene with four different FCC gasoline compounds (2,3-dimethyl-2-butene, n-heptane, 2-methylbutane and 2,3-dimethyl-1-butene) were measured at 101.33 kPa with a circulation still. All the four binary systems exhibit positive deviations from ideal solution behavior. Especially, thiophene + n-heptane binary system exhibits maximum pressure homogeneous azeotrope at 356.33 K with the composition 0.8499 for thiophene. All the VLE measurements passed the thermodynamic consistency test. Wilson model was used to correlate the experimental VLE data. The infinite dilution activity coefficients for the systems were also presented. The experimental data of thiophene + 2,3-dimethyl-2-butene and thiophene + 2,3-dimethyl-1-butene were correlated by original UNIFAC and UNIFAC-Dortmund models. The interaction parameters of the binary pair C 4H 4S functional group and C C functional group for the two models were obtained and they were tested reliable by some literature data.

Finding a suitable thermodynamic model and phase equilibria for hydrodeoxygenation reactions of methyl heptanoate

Replacement of fossil fuels with biomass-based components is of increasing public and scientific interest. Unfortunately, most biomass-based compounds contain oxygen and oxygen content must be diminished before use of the compounds as fuel. Removal is usually done catalytically, with hydrogen supplied to convert the oxygen to water. Hydrodeoxygenation (HDO) of biomass-based compounds is often studied with model compounds, and the system investigated here was methyl heptanoate+m-xylene. Modeling of the reaction kinetics requires that behavior of the reaction mixture as a function of reaction time must be described. A suitable thermodynamic model for non-ideal system at high pressure and temperature is needed, and this demands correct modeling of the solubility of hydrogen and the water of reaction. For validation of the thermodynamic models isothermal vapor–liquid equilibrium (VLE) for the methyl heptanoate+m-xylene system was measured at 398.15K and 408.15K with a circulation still. The experimental VLE exhibited slight negative deviation from Raoult’s law. No azeotropic behavior was found. The experimental VLE results were correlated with the Wilson model with temperature-dependent parameters and used in testing of the SRK, original UNIFAC, UNIFAC-Dortmund, and PSRK predictive models. PSRK was preferred for further estimations. All VLE measurements passed the point consistency tests. Simulated reaction conditions for HDO of methyl heptanoate at the initial and final points were calculated to determine the effect of vapor–liquid equilibrium on the composition of reaction mixtures.

Evaluation of Group-Contribution Methods To Predict VLE and Odor Intensity of Fragrances

Several predictive GE methods based on the group-contribution concept have been tested for prediction of multicomponent vapor–liquid equilibria (VLE) of fragrance mixtures. The evaluation covered 24 binary, 20 ternary, and 21 quaternary mixtures combining six different fragrances typically used in perfume formulation and ethanol as the solvent. The selected predictive methods are the original UNIFAC (updated to the last revision), the UNIFAC-Dortmund, the ASOG, and the A-UNIFAC. The equilibrium compositions were experimentally measured at 23 °C by headspace gas chromatography (HS-GC). For each liquid composition, the corresponding experimental and predicted vapor compositions were compared. This study confirmed that the UNIFAC method is the best predictive model for prediction of VLE, while the A-UNIFAC performed poorer than other evaluated methods for the mixtures studied in this work. Moreover, from the vapor composition the odor intensity and character of the fragrance mixtures was calculated using a p...

(Liquid + liquid) equilibria of methanol + isooctane + methylcyclohexane + ethylbenzene quaternary system at T = 303.15 K

Tie line data of {methanol + isooctane + methylcyclohexane}, {methanol + ethylbenzene + methylcyclohexane}, and {methanol + ethylbenzene + isooctane} ternary systems were obtained at T = 303.15 K. A quaternary system {methanol + isooctane + methylcyclohexane + ethylbenzene} was also studied at the same temperature. In order to obtain the binodal surface of the quaternary system, four quaternary sectional planes with several methylcyclohexane/isooctane ratios were studied. Experimental results show that the binodal surface in the solid diagram is small and that the highest ethylbenzene mass fraction values beyond which only one phase is present for the methanol-rich phase and hydrocarbon-rich one, respectively, are: 0.0783 and 0.0864 for P1, 0.0791 and 0.0906 for P2, 0.0798 and 0.0805 for P3, 0.0812 and 0.0935 for P4. So, if this quaternary system contains the correct methanol and hydrocarbons concentrations, this blend can be used as a reformulated gasoline because no phase separation should be observed. The distribution of ethylbenzene between both phases was also analysed. Ternary experimental results were correlated with the UNIQUAC and NRTL equation, and predicted with the original UNIFAC group contribution method. The equilibrium data of the three ternary systems were used to determine interactions parameters for the UNIQUAC equation. The UNIQUAC and NRTL equations are more accurate than the UNIFAC method for the ternary systems studied here, because this last model predicts an immiscibility region larger than the experimentally observed in the methanol-rich phase. The UNIQUAC equation fitted to the experimental data is more accurate than the UNIFAC method for this quaternary system.

Isobaric vapor–liquid equilibria for binary and ternary mixtures with cyclohexane, cyclohexene, and morpholine at 100 kPa

Vapor–liquid equilibria (VLE) data at 100 kPa have been determinated for the ternary system cyclohexane + cyclohexene + morpholine and two constituent binary systems cyclohexane + morpholine and cyclohexene + morpholine. The thermodynamic consistency of experimental data has been verified. Both binary systems deviate moderately from ideality without the presence of an azeotrope. The VLE data have been well correlated using local composition models (Wilson, NRTL and UNIQUAC) and have been also predicted with the original UNIFAC.

Phase equilibria for systems containing dimethyl disulfide and diethyl disulfide with hydrocarbons at 368.15 K

Isothermal vapor–liquid equilibrium (VLE) for dimethyl disulfide + toluene, dimethyl disulfide + 2,2,4-trimethylpentane, dimethyl disulfide + 2,4,4-trimethyl-1-pentene, and diethyl disulfide + 2,2,4-trimethylpentane at 368.15 K were measured with a recirculation still. All systems exhibit positive deviation from Raoult's law. Dimethyl disulfide + toluene system shows only slight positive deviation from Raoult's law, while dimethyl disulfide + 2,2,4-trimethylpentane, dimethyl disulfide + 2,4,4-trimethyl-1-pentene, and diethyl disulfide + 2,2,4-trimethylpentane systems show larger positive deviation from Raoult's law. Maximum pressure azeotropes were found in systems: dimethyl disulfide + toluene ( x 1 = 0.632, P = 66.4 kPa, T = 368.15 K), dimethyl disulfide + 2,2,4-trimethylpentane ( x 1 = 0.311, P = 95.8 kPa, T = 368.15 K), and dimethyl disulfide + 2,4,4-trimethyl-1-pentene ( x 1 = 0.295, P = 88.4 kPa, T = 368.15 K). No azeotropic behavior was observed in system diethyl disulfide + 2,2,4-trimethylpentane at 368.15 K. The experimental results were correlated with the Wilson model. Original UNIFAC was used to predict dimethyl disulfide + 2,2,4-trimethylpentane and diethyl disulfide + 2,2,4-trimethylpentane systems at 368.15 K. COSMO-SAC predictive model was used to predict infinite dilution activity coefficients for all systems measured. Liquid and vapor-phase composition were determined with gas chromatography. All VLE measurements passed the thermodynamic consistency tests applied. The activity coefficients at infinite dilution are also presented.

Phase equilibria on five binary systems containing 1-butanethiol and 3-methylthiophene in hydrocarbons

Isothermal vapor–liquid equilibrium (VLE) of the following systems was measured with a recirculation still: 1-butanethiol + methylcyclopentane at 343.15 K, 1-butanethiol + 2,2,4-trimethylpentane at 368.15 K, 3-methylthiophene + toluene at 383.15 K, 3-methylthiophene + o-xylene at 383.15 K, and 3-methylthiophene + 1,2,4-trimethylbenzene at 383.15 K. 1-Butanethiol + methylcyclopentane and 1-butanethiol + 2,2,4-trimethylpentane systems exhibit positive deviation from Raoult's law, whereas systems containing 3-methylthiophene in aromatic hydrocarbons exhibit only slight positive deviation from Raoult's law. A maximum pressure azeotrope was found in the system 1-butanethiol + 2,2,4-trimethylpentane ( x 1 = 0.548, P = 100.65 kPa, T = 368.15 K). The experimental results were correlated with the Wilson model and compared with original UNIFAC and COSMO-SAC predictive models. Raoult's law can be used to describe the behavior of 3-methylthiophene in aromatic hydrocarbons at the experimental conditions in this work. Liquid and vapor-phase composition were determined with gas chromatography. All measured data sets passed the thermodynamic consistency tests applied. The activity coefficients at infinite dilution are also presented.

Phase equilibria of binary systems of 3-methylthiophene with four different hydrocarbons

Isothermal vapor–liquid equilibrium (VLE) for systems 3-methylthiophene + 2-methylpentane at 333.15 K, 3-methylthiophene + n-hexane at 333.15 K, 3-methylthiophene + methylcyclopentane at 343.15 K, and 3-methylthiophene + methylcyclohexane at 373.15 K were measured with a recirculation still. All systems exhibit positive deviation from Raoult's law. No azeotropic behavior was found in any of the systems at the measured temperatures. The experimental results were correlated with the Wilson model and also compared with the original UNIFAC and UNIFAC-Dortmund predictive models. Liquid and vapor-phase composition were determined with gas chromatography. All VLE measurements passed the used thermodynamic consistency tests (integral, infinite dilution and point test). The activity coefficients at infinite dilution are also presented.

Prediction of Vapor−Liquid Equilibrium at High Pressure Using a New Excess Free Energy Mixing Rule Coupled with the Original UNIFAC Method and the SRK Equation of State

A new excess free energy mixing rule that employs a low-pressure reference state is proposed in this work. This new low-pressure mixing rule (LPMR), coupled with the original UNIFAC method and the Soave−Redlich−Kwong (SRK) equation of state (EoS), leads to an improved EoS/GE predictive model (LPMR−SRK model) that was applied to the high-pressure vapor−liquid phase equilibria of various systems including symmetric and asymmetric systems of n-alkanes with different gases (C2H6, C3H8, CO2, H2) and polar systems. The results are compared with those of other EoS/GE predictive models, such as the predictive Soave−Redlich−Kwong (PSRK), Chen-modified PSRK (MPSRK), volume-translated Peng−Robinson group contribution equation of state (VTPR), and linear combination of the Vidal and Michelsen rules (LCVM) models. It is demonstrated that LPMR−SRK method gives similar accuracy as the PSRK approach for symmetric or slightly asymmetric systems and gives better results than the MPSRK, VTPR, and LCVM models. For highly asy...