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The objective of this work was to study the behavior of the azeotropic points of the methanol + DMC system under elevated pressures. We obtained isothermal vapor–liquid equilibria (VLE) data for this system at 383.15, 403.15, and 413.15 K by a static method. The azeotropic points were determined from the experimental VLE data. The temperature and pressure dependencies of the determined azeotropic points are discussed and compared with ones measured at reduced pressure. The experimental VLE data were represented by two activity coefficient models (non-random two-liquid and Wilson models). We also tested the modified UNIFAC (Dortmund) model for prediction of the VLE and azeotropic points. The azeotropic points of this system could be obtained over the pressure range from reduced pressures to elevated ones.

Isothermal P–x vapor–liquid equilibrium and excess enthalpy (HE) data were experimentally determined for the 10 binary systems hexane, heptane, 1-octene, benzene, toluene, ethanol, methanol, ethyl acetate, dibutyl ether, and dichloromethane with N,N- dimethylacetamide using the static synthetic method and isothermal flow calorimetry, respectively. The experimental data from this work together with data taken from literature were used for the extension of the group contribution method Modified UNIFAC (Dortmund).

For process development and simulation, the group contribution concept can be successfully applied for the estimation of the missing pure component and mixture properties. This concept has the great advantage that only a limited number of group interaction parameters is required. With the support of a company consortium founded 1996 at the University of Oldenburg, the group contribution model modified UNIFAC (Dortmund) for the prediction of phase equilibria and excess properties has been continuously revised and extended. Within the consortium the number of available group interaction parameters has been doubled. At the same time, the reliability of the results was greatly improved, and the range of applicability was extended to ionic liquids, polyethers, and so forth, and systems for which no experimental data are available, e.g., reactive systems. In this paper the group interaction parameters for the sulfur groups sulfones, sulfides, and disulfides are given. Furthermore, the current status of the cons...

The development and design of chemical processes are carried out by solving the balance equations of a mathematical model for sections of or the whole chemical plant with the help of process simulators. For process simulation, besides kinetic data for the chemical reaction, various pure component and mixture properties are required. Because of the great importance of separation processes for a chemical plant in particular, a reliable knowledge of the phase equilibrium behavior is required. The phase equilibrium behavior can be calculated with the help of modern equations of state or gE–models using only binary parameters. But unfortunately, only a very small part of the experimental data for fitting the required binary model parameters is available, so very often these models cannot be applied directly. To solve this problem, powerful predictive thermodynamic models have been developed. Group contribution methods allow the prediction of the required phase equilibrium data using only a limited number of group interaction parameters. A prerequisite for fitting the required group interaction parameters is a comprehensive database. That is why for the development of powerful group contribution methods almost all published pure component properties, phase equilibrium data, excess properties, etc., were stored in computerized form in the Dortmund Data Bank. In this review, the present status, weaknesses, advantages and disadvantages, possible applications, and typical results of the different group contribution methods for the calculation of phase equilibria are presented.

Liquid–liquid equilibria (LLE) of water + acetic acid + dimethyl carbonate were experimentally specified at (298.2, 308.2, and 318.2) K. Each diagram was obtained through specifying binodal curves and tie-lines. The reliability of the experimental tie-line data was calculated by the Othmer–Tobias correlation. The nonrandom two-liquid (NRTL) and unified quasichemical activity coefficient (UNIQUAC) models were used to obtain the binary interaction parameters of the experimental tie-line data. However, universal functional (UNIFAC) and modified UNIFAC methods were used as well to predict the phase equilibrium in the system specified from experimental data using the interaction parameters between CH3, OCOO, COOH, and H2O functional groups. Distribution coefficients and separation factors were assessed for the immiscibility region.

The objective of this study is the selection of a suitable entrainer for the separation of the binary azeotropic mixture, namely methanol + dimethyl carbonate (DMC) by extractive distillation. In this study, 2-ethoxyethanol and 4-methyl-2-pentanone were considered as entrainer candidates for the separation of methanol and DMC. Isobaric vapor–liquid equilibria (VLE) were measured for the ternary mixtures methanol + DMC + 2-ethoxyethanol and methanol + DMC + 4-methyl-2-pentanone, and for their constituent binary mixtures, under reduced pressures of 66.66 kPa and 93.32 kPa. Experimental VLE data for the constituent binary mixtures were represented by the Wilson and the NRTL model. The VLE predictions for two ternary mixtures were compared with the experimental VLE data on the basis of the Wilson or NRTL parameters obtained from the constituent binary VLE data. The modified UNIFAC (Dortmund) model was also used for the prediction of the binary and ternary mixtures. The solvent effects of the two entrainer candidates investigated are discussed using the predicted results for the ternary mixtures and both 2-ethoxyethanol and 4-methyl-2-pentanone were found to be suitable entrainers for the separation of methanol and DMC. When the selectivity of 2-ethoxyethanol and 4-methyl-2-pentanone are compared, it could be concluded from the separation factors that 4-methyl-2-pentanone shows a higher selectivity.

The solubilities of NaCl, KCl, LiCl, and LiBr in pure methanol, ethanol, and acetone were measured over a temperature range from 293.15 to 333.15 K. Furthermore salt solubilities in the mixed solvents (water + methanol, water + ethanol, water + acetone, methanol + ethanol, methanol + acetone, ethanol + acetone) were determined at 313.15 K. For a few systems solubility data are reported for the first time. In a few cases a comparison with published data stored in the Dortmund Data Bank (DDB)(1) showed disagreement. The LIQUAC model was used to correlate the experimental data. The calculated salt solubilities are in good agreement with the experimental results for the systems NaCl + water + methanol and KCl + water + methanol.

This article presents a comparative study about the predictive capability of COSMO-SAC and COSMO-RS(Ol) models with respect to excess enthalpies of various binary systems. Results of the group cont...

This research has been focused on viscosities, vapor−liquid equilibria (VLE), and heat of mixing measurements for water with the following choline-based ionic liquids: choline lactate, choline glycolate, and choline methanesulfonate. Isothermal vapor−liquid equilibria were measured by means of a static VLE apparatus at (303.15, 313.15, and 323.15) K. The experimental VLE data were correlated using the NRTL and UNIQUAC models, and the root-mean-square deviations (rmsd's) are given. Furthermore, the molar excess enthalpies of water + choline glycolate and water + choline lactate ionic liquid systems have been performed at T = (303.15, 315.15, and 323.15) K using a differential scanning calorimeter. The results were fitted to a Redlich−Kister equation to determine the fitting parameters and the mean relative deviations. Viscosities of the binary aqueous systems with choline glycolate and choline lactate have been measured at 293.15 K.

Vapour–liquid equilibrium (VLE) data for the binary systems ethanol+methyl propanoate and ethanol+methyl butanoate at 326.30 and 346.30 K and vapour pressures (VPs) for both esters were measured by a circulation method. The two systems exhibit azeotropic behaviour. The VLE data were correlated using the Redlich–Kister, Wilson and NRTL equations. Molar excess volumes for the binary systems at 298.15 K were determined and correlated.

Reliable azeotropic data have been measured for the binary systems ethanol+diethoxymethane, diethoxymethane+1-propanol, diethoxymethane+heptane, and cyclohexane+diethoxymethane with the help of a wire band column. Additionally molar excess enthalpies (HE) for the binary mixtures of diethoxymethane with hexane, 1-octene, methanol and ethanol at 363.15 K have been determined with an isothermal flow calorimeter. The experimental data were compared with the results using the available “ether” main group of the group contribution method Modified UNIFAC (Dortmund), which is a well-known model for the prediction of phase equilibria and excess properties. For the description of the HE data a Redlich–Kister polynomial was also used. The aim of this work is to supplement the available data base for acetal systems required for the introduction of a new “acetal” group in the Modified UNIFAC (Dortmund) model.

Solid−liquid equilibria (SLE) for the following seven systems have been measured by the visual technique: benzene, toluene, cyclohexane, 1-propanol, methanol, water, and 2-pentanone with e-caprolactone. For the description of the SLE data the NRTL model and the group contribution method Modified UNIFAC (Dortmund) were used.

Predictions of vapor–liquid equilibria at high temperatures and pressures were obtained by applying a modified procedure using the Huron–Vidal mixing rule based on available activity coefficients at infinite dilution and low pressures. These activity coefficients were calculated with so-called conductor-like screening model for real solvents (COSMO-RS) and with a variation of this model, known as segment activity coefficient (COSMO-SAC) model. In this work, the performances of the mixing rule (HVID model) coupled with the SRK equation of state and a reduced UNIQUAC model are presented for six binary systems and a ternary system, whose VLE data are available over a large temperature and pressure range.