共查询到20条相似文献,搜索用时 397 毫秒
1.
2.
This paper deals with the possibility of estimating UNIFAC parameters from infinite dilution activity coefficients. Such activity coefficients can be obtained from gas chromatographic measurements (GLC). In some cases the original UNIFAC equations do not represent very well the variations of the activity coefficients with the concentration in the very dilute regions. It is then not possible to estimate reliable parameters from infinite dilution activity coefficients alone. It is shown that a recent modification of the combinatorial part of the UNIFAC equations allows for the estimation of UNIFAC parameters from infinite dilution activity coefficients for alkane—-ketone, alkane—-alcohol, and other mixtures. 相似文献
3.
Steen Skjold-Jørgensen Peter Rasmussen Aage Fredenslund 《Chemical engineering science》1982,37(1):99-111
The UNIQUAC/UNIFAC models can not in general represent vapor-liquid and liquid-liquid equilibria simultaneously with satisfactory results. Recent modifications of the models take into account association and solvation effects by means of chemical theory. However, this approach leads to complicated expressions for the activity coefficients and the improvements are only moderate. A modification of the UNIQUAC/UNIFAC models is presented which takes into account solvation and association by allowing the interaction energies to vary with composition. This approach leads to explicit expressions for the activity coefficients. It is shown that the modified models in simultaneous correlations lead to quantitative representation of vapor-liquid equilibrium data and semi-quantitative representation of binary and ternary liquid-liquid equilibrium data. 相似文献
4.
5.
Tiziana Fornari Susana Bottini Esteban A. Brignole 《Journal of the American Oil Chemists' Society》1994,71(4):391-395
The prediction of the vapor-liquid equilibria of vegetable oil-hexane mixtures is studied. Activity coefficients are calculated
by the UNIFAC model. Different entropic contributions to activity coefficients from the literature are analyzed. These modifications
improve the performance of the original UNIFAC model in vapor-liquid equilibrium calculations. 相似文献
6.
Effect of activity coefficient models on predictions of secondary organic aerosol partitioning 总被引:1,自引:0,他引:1
Several available models for predicting organic aerosol activity coefficients are compared by examining their effect on predictions of secondary organic aerosol (SOA) concentrations and aerosol water uptake in laboratory and atmospheric systems. Activity coefficient models studied include Ideal behavior, the Wilson and NRTL equations, and UNIFAC in standard form, with revised interaction parameters, and with no temperature dependence. Wilson and NRTL binary interaction parameters were fit from UNIFAC predictions of activity coefficients. SOA model simulations were performed for different combinations of primary organic aerosol (POA) composition, SOA composition, and relative humidity. All of the activity coefficient methods predict similar results for mixtures of similar components, but for highly dissimilar aerosol mixtures, the Ideal, Wilson and NRTL models tend to predict higher SOA concentrations and aerosol water uptake compared to UNIFAC. Different versions of UNIFAC gave nearly identical results for most scenarios. Computational requirements are lowest for Ideal, followed by Wilson, and then NRTL and UNIFAC models. 相似文献
7.
A computer algorithm is presented which predicts thermophysical properties of mixtures using only two-dimensional chemical structures. It applies a combination of techniques for the analysis of group contributions and other characteristics of a chemical structure in a table-driven format. These techniques are used to examine the error behavior for predictions of critical properties and saturated properties. UNIFAC predictions of activity coefficients are combined with pure-component properties to demonstrate that accurate estimates of azeotrope behavior and K-values can be obtained. 相似文献
8.
Zur Auslegung von Trennanlagen und für viele andere praktische Zwecke benötigt man die quantitative Kenntnis des Phasengleichgewichts. Dieses Phasengleichgewicht kann mit Hilfe von neueren Ansätzen für die Gibbssche Exzeßenthalpie recht gut aus den binären Konstanten berechnet werden. Da jedoch die Anzahl der technisch interessanten Systeme sehr groß ist, wird man in vielen Fällen nicht für alle beteiligten binären Systeme Phasengleichgewichtsdaten in der Literatur finden. In diesen Fällen ist es notwendig, die benötigte Information mit Hilfe allgemein anwendbarer Methoden vorauszuberechnen. Zur Zeit liefern die Inkrementenmethoden (ASOG , UNIFAC ) die besten Resultate. Bei diesen Inkrementenmethoden wird die flüssige Phase wie eine Mischung von funktionellen Gruppen behandelt. Dies hat den Vorteil, daß eine große Zahl technisch interessanter Systeme mit einer relativ geringen Anzahl von Parametern, die die Wechselwirkung zwischen den Gruppen beschreiben, berechnet werden kann, da die Anzahl der verschiedenen Strukturgruppen viel kleiner ist als die Anzahl der möglichen unterschiedlichen Moleküle. In diesem Übersichtsartikel sollen die Möglichkeiten der UNIFAC -Methode zur Berechnung von Phasengleichgewichten demonstriert werden. Die UNIFAC -Methode heute für Nichtelektrolytsysteme im Temperaturbereich von 275 bis 425 K und Drücke bis 10 bar anwendbar. A survey of the calculation of phase equilibria with the aid of the UNIFAC -Methode. In the design of diffusional separation processes and for many other practical purposes one needs quantitative estimates of phase equilibrium compositions. These compositions can today be predicted with good results using modern, two-parameter models for the excess Gibbs energy. However, since the number of different multicomponent mixtures of interest in chemical technology is very large, it is in practise often not possible to find experimental data in the literature for all the possible binary combinations. In these cases it is necessary to use a predictive approach. Today, group-contribution methods such as ASOG and UNIFAC may be used with confidence to predict liquid phase excess Gibbs energies. In these methods, the mixture is assumed to consist not of molecules but of the functional groups which, when added form the parent molecules. This has the advantage that a large number of mixtures of interest in chemical technology can be described in terms of relatively few parameters characterizing the interactions between the groups. This review article demonstrates the application of the UNIFAC method to various practical problems within phase equilibria. The UNIFAC method applies to mixtures of nonelectrolytes in the temperature range of 275–425 K and at pressures up to 10 bar. 相似文献
9.
The solubility parameter scheme is an exceptionally useful tool for predicting the solubility behavior of simple polymer systems. However, this scheme is unable to handle well enough complicated systems, such as those involving donor-acceptor interactions and those containing more than two solvents. More advanced thermodynamic treatments and computer techniques, such as UNIFAC, can be a key to solving these kinds of problems. The UNIFAC group-contribution method utilizes a volume parameter and a surface-area parameter for each structural group and a pair of interaction-energy parameters for each pair of groups, which can be deduced from experimental activity data. The method was originally derived for mixtures of ordinary liquids and has been extended to polymer solutions by adding a free-volume correction. The modified UNIFAC method can be used to estimate the activities of solvents in a polymer solution, even when no experimental data are available for the mixture. In the present study, the UNIFAC method was applied to optimize polymer-solvent interactions in three-solvent systems. A three-dimensional plot, displaying polymer activity as a function of the solvent composition, was constructed for each polymer system. The minimum in polymer activity was used as the criterion for maximum polymer-solvent interaction. Dissolution rate and solution clarity were used to test the polymer-solvent interaction experimentally. Comparison of theoretical predictions with experimental results indicated that a better agreement could be obtained by using the UNIFAC method rather than the solubility parameter method. 相似文献
10.
A computational procedure using a modification of Boston and Sullivan's “inside-out” multistage multicomponent separation algorithm (1974) is developed. In order to improve convergence behavior for problems involving mixtures with highly nonideal liquid phases, a two-parameter model is used to describe liquid-phase compositional effects upon the K-factor. The quasi-Newton methods of Mehra et al. (1983) and Nghiem (1983) are applied to solving various sets of solution variables in the proposed algorithm. Activity coefficients are calculated using the UNIQUAC activity-coefficient model (1975) with parameters obtained from the UNIFAC group-contribution method (1975). The computational procedure is applicable to distillation, absorption and reboiled-absorption configurations. The proposed algorithm was implemented in a FORTRAN 77 program and tested on the Honeywell DPS 8/70M computer at the University of Calgary. Inclusion of the liquid-phase model resulted in improved convergence behavior for nonideal systems in which the original “inside-out” method failed to converge. 相似文献
11.
12.
Dr.-Ing. Julie Damay Dr. Gleb Ryzhakov JP Dr.-Ing. Fabian Jirasek Prof. Dr.-Ing. Hans Hasse Prof. Ivan Oseledets Prof. Dr. Michael Bortz 《化学,工程师,技术》2023,95(7):1061-1069
Knowledge of thermodynamic properties of mixtures is essential in many fields of science and engineering. However, the experimental data is usually scarce, so prediction methods are needed. Matrix completion methods have proven to be very successful in predicting thermodynamic properties of binary mixtures. In this approach, the experimental data is organized in a matrix whose rows and columns correspond to the two components, and whose entries indicate the value of the studied thermodynamic property at fixed conditions. In the present work, we extend the concept to tensor completion methods (TCMs). This allows to account for the variation of the studied property depending on the chosen conditions. The feasibility is demonstrated by applying a TCM to predict activity coefficients at infinite dilution. The third dimension of the tensor is used to describe the influence of the temperature. The TCM is shown to yield better predictions than the well-established UNIFAC method. Furthermore, the proposed TCM is able to learn and unveil the physical law describing the temperature dependence of activity coefficients from the scarce experimental mixture data only. 相似文献
13.
Yichun Dong Shuai Huang Yanyan Guo Zhigang Lei 《American Institute of Chemical Engineers》2020,66(1):e16787
The united chemical thermodynamic model, that is, COSMO-UNIFAC model was first extended to the systems containing ionic liquids (ILs). This model for ILs combines the respective advantages of COSMO-based (priori prediction) and UNIFAC (relatively accurate prediction) models. The comparison of the predicted values by COSMO-UNIFAC model with experimental data indicates that this model can provide a moderate quantitative prediction for the systems containing ILs when the UNIFAC model parameters are vacant. 相似文献
14.
介绍了高分子溶液中基团贡献活度系数模型、基团贡献状态方程、高分子密度计算的基团贡献法以及它们的最新进展。 相似文献
15.
Liquid-liquid equilibrium (LLE) data for the ternary system water-ethanol-dimethyl succinate have been determined experimentally at temperatures ranging from 298.15 to 318.15K at 5K intervals. Complete phase diagrams were obtained by determining solubility and the tie-line data. Tie-line compositions were correlated by Othmer-Tobias method. The universal quasichemical functional group activity coefficient (UNIFAC) and modified UNIFAC methods were used to predict the phase equilibrium in the system using the interaction parameters determined from experimental data between groups CH3, CH2, OH, CH3COO and H2O. It is found that UNIFAC and modified UNIFAC group interaction parameters used for LLE could not provide a good prediction. Distribution coefficients and separation factors were evaluated for the immiscibility region. 相似文献
16.
17.
18.
无限稀释活度系数的预测模型 总被引:2,自引:0,他引:2
全面比较了几种常用模型对各类体系的无限稀释活度系数的预测结果,讨论了各模型适用范围和优缺点。针对现有模型的不足,对烃类体系提出了改进模型,与已有模型相比,新模型型具有简单易用、且精度较高的优点。 相似文献
19.
20.
The excess Cibbs energy of liquid mixtures may be predicted using group contribution models (f.ex. UNIFAC and ASOG), or it may be correlated using molecular models such as UNIQUAC. Group contribution models and the UNIQUAC model contain a combinatorial contribution which accounts for size- and shape-effects and a residual contribution which accounts for interactions among groups or molecules. A new expression for the combinatorial contribution is given which yields much improved predictions of the excess Gibbs energy of systems where the residual contribution may be expected to be zero (e.g., mixtures of aliphatic hydrocarbons). It is shown that it is advantageous to incorporate the new combinational expression into future modifications of the UNIFAC model. 相似文献