A modified UNIFAC model. 2. Present parameter matrix and results for different thermodynamic properties
01 Jan 1993-Industrial & Engineering Chemistry Research (American Chemical Society)-Vol. 32, Iss: 1, pp 178-193
TL;DR: In this paper, a modified UNIFAC (Dortmund, FRG) method was proposed to fit temperature-dependent group interaction parameters simultaneously to vapor-liquid equilibrium (VLE), liquid liquid equilibrium (LLE), h E, and γ ∞ data.
Abstract: Several years ago a modified UNIFAC (Dortmund, FRG) method was proposed, which shows various advantages when compared with the group contribution methods UNIFAC or ASOG; the latter are used worldwide for the synthesis and design of rectification processes. These advantages were reached by using a modified combinatorial part and by using a large data base to fit temperature-dependent group interaction parameters simultaneously to vapor-liquid equilibrium (VLE), liquid-liquid equilibrium (LLE), h E , and γ ∞ data. The main advantages of the modified UNIFAC method are a better description of the temperature dependence and the real behavior in the dilute region and that it can be applied more reliably for systems involving molecules very different in size. To increase the range of this applicability, the temperature-dependent group interaction parameters of the modified UNIFAC has been fitted for 45 main groups using phase equilibrium information (VLE, h E , γ ∞, LLE) stored in the Dortmund Data Bank. A comprehensive comparison with the results of other group contribution methods confirms the high reliability of the modified UNIFAC (Dortmund) method
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TL;DR: COSMO-RS as mentioned in this paper is a general and fast methodology for the a priori prediction of thermophysical data of liquids, which is based on cheap unimolecular quantum chemical calculations, combined with exact statistical thermodynamics, provide the information necessary for the evaluation of molecular interactions in liquids.
Abstract: COSMO-RS, a general and fast methodology for the a priori prediction of thermophysical data of liquids is presented. It is based on cheap unimolecular quantum chemical calculations, which, combined with exact statistical thermodynamics, provide the information necessary for the evaluation of molecular interactions in liquids. COSMO-RS is an alternative to structure interpolating group contribution methods. The method is independent of experimental data and generally applicable. A methodological comparison with group contribution methods is given. The applicability of the COSMO-RS method to the goal of solvent screening is demonstrated at various examples of vapor–liquid-, liquid–liquid-, solid–liquid-equilibria and vapor-pressure predictions.
1,357 citations
TL;DR: A comprehensive review of phase change materials (PCMs) with phase transition temperatures between 0 and 250°C is presented in this paper, with the focus on this temperature range is due to potential CO 2 emissions reduction able to be achieved replacing conventional heating and cooling applications in the domestic, commercial and public administration sectors, which represented around a quarter of the UK's final energy consumption in 2015.
755 citations
Cites methods from "A modified UNIFAC model. 2. Present..."
...More developed techniques to 155 predict thermophysical properties of eutectic mixtures do exist [71], [72], involving Van Der Waals 156 volumes and surface areas of stable molecular combinations; however, more simplified correlations 157 were used....
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TL;DR: In this paper, an activity coefficient model using molecular solvation based on the COSMO-RS method is proposed, which requires only a single radius for each atom in the solvation calculations, one universal parameter to discern hydrogen-bond acceptors and donors, and two universal parameters to determine segment interactions.
Abstract: An activity coefficient model using molecular solvation based on the COSMO-RS method is proposed. In this model, quantum mechanical COSMO calculations are performed to obtain the screening charges for molecules in a perfect conductor. A statistical mechanical model that considers molecules to be a collection of surface segments is developed for the calculation of segment activity coefficients using these screening charges. Activity coefficients for molecules are then obtained by summing the contributions of the segments. This model requires only a single radius for each atom in the COSMO solvation calculations, one universal parameter to discern hydrogen-bond acceptors and donors, and two universal parameters to determine segment interactions. This is a significantly fewer number of parameters for phase equilibrium calculations than group contribution methods such as the UNIFAC (168 parameters) and modified UNIFAC (612 parameters) models. The resulting completely a priori prediction method results in abso...
721 citations
TL;DR: This review presents a short delineation of the theory, the application potential and limitations of COSMO-RS, and its most important application areas.
Abstract: The conductor-like screening model for realistic solvation (COSMO-RS) method has been established as a novel way to predict thermophysical data for liquid systems and has become a frequently used alternative to force field-based molecular simulation methods on one side and group contribution methods on the other. Through its unique combination of a quantum chemical treatment of solutes and solvents with an efficient statistical thermodynamics procedure for the molecular surface interactions, it enables the efficient calculation of many properties that other methods can barely predict. This review presents a short delineation of the theory, the application potential and limitations of COSMO-RS, and its most important application areas.
451 citations
TL;DR: In this paper, the authors measured the VLE for six systems at 353 K and activity coefficients at infinite dilution (γ∞) for various solutes (alkanes, alkenes, cycloalkanes and cyclo-alkenes, aromatics, alcohols, ketones, esters, ethers, and water) in the ionic liquids.
381 citations
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28,888 citations
TL;DR: A method is described for the minimization of a function of n variables, which depends on the comparison of function values at the (n 41) vertices of a general simplex, followed by the replacement of the vertex with the highest value by another point.
Abstract: A method is described for the minimization of a function of n variables, which depends on the comparison of function values at the (n 41) vertices of a general simplex, followed by the replacement of the vertex with the highest value by another point. The simplex adapts itself to the local landscape, and contracts on to the final minimum. The method is shown to be effective and computationally compact. A procedure is given for the estimation of the Hessian matrix in the neighbourhood of the minimum, needed in statistical estimation problems.
27,271 citations
TL;DR: In this article, a group-contribution method is presented for the prediction of activity coefficients in nonelectrolyte liquid mixtures, which combines the solution-of-functional-groups concept with a model for activity coefficients based on an extension of the quasi chemical theory of liquid mixture (UNIQUAC).
Abstract: A group-contribution method is presented for the prediction of activity coefficients in nonelectrolyte liquid mixtures. The method combines the solution-of-functional-groups concept with a model for activity coefficients based on an extension of the quasi chemical theory of liquid mixtures (UNIQUAC). The resulting UNIFAC model (UNIQUAC Functional-group Activity Coefficients) contains two adjustable parameters per pair of functional groups.
By using group-interaction parameters obtained from data reduction, activity coefficients in a large number of binary and multicomponent mixtures may be predicted, often with good accuracy. This is demonstrated for mixtures containing water, hydrocarbons, alcohols, chlorides, nitriles, ketones, amines, and other organic fluids in the temperature range 275° to 400°K.
2,787 citations
TL;DR: In this paper, the parameters for 46 group combinations are provided and a new main group for sulfones is introduced, for which the group interaction parameters for eight main groups are fitted.
Abstract: The group contribution method UNIFAC has become very popular because of its large range of applicability and its reliable predictions of vapor−liquid equilibria. With the help of new data stored in the Dortmund Data Bank (DDB), many gaps in the existing UNIFAC parameter matrix have been filled, and many new main groups have been added to the parameter table. In this paper, the parameters for 46 group combinations are provided. Additionally, a new main group for sulfones is introduced, for which the group interaction parameters for eight main groups are fitted.
1,135 citations
TL;DR: Modification de la methode UNIFAC de telle maniere que l'equilibre liquide-vapeur, les coefficients d'activites pour des dilutions infinies and les enthalpies de melange puissent etre calcules suffisamment exactement avec un seul set of parametres as discussed by the authors.
Abstract: Modification de la methode UNIFAC de telle maniere que l'equilibre liquide-vapeur, les coefficients d'activites pour des dilutions infinies et les enthalpies de melange puissent etre calcules suffisamment exactement avec un seul set de parametres
703 citations