UNIFAC


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AcronymDefinition
UNIFACUniversal quasichemical Functional group Activity Coefficients
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The experimental literature data and estimation by the modified UNIFAC method show that the most probable values for the limiting activity coefficient at 298.15 K (using volume fraction convention [a.sub.i] = [[gamma].sub.i][[phi].sub.i]) are 3.4 for benzene in methanol [50-52], 48.3 for methanol in benzene as estimated by the modified UNIFAC method [43, 53-55], 4.2 for benzene in 2-butanol and 6.9 for 2-butanol in benzene.
Table-3 lists the g values in various solvents calculated according to UNIFAC model reported by Fredenslund et al.
A modified UNIFAC model 2: Present parameter matrix and results for different thermodynamic properties [documento en linea].
La idea central de UNIFAC es reducir la informacion de equilibrio de fases a parametros de interaccion entre grupos estructurales, siguiendo el concepto original de Langmuir de que las interacciones fisicas entre moleculas pueden estimarse sumando interacciones entre los grupos funcionales que las forman (Fredenslund et al., 1975; Fredenslund et al., 1977a; Fredenslund et al., 1977b).
KEYWORDS: Bio-diesel, Extractive reaction, Simulation, Transesterification, UNIFAC.
The combinatorial component of the UNIFAC group contribution theory, [[gamma].sub.c], deals with geometric interaction between molecules, and is applicable even in the absence of non-ideal interactions.
Two group-contribution, lattice-fluid models have been used to predict the solubilities in the polymer-solvent system: the van der Waals UNIFAC free-volume model (UNIFAC vdw-FV) and the group-contribution, lattice-fluid equation-of-state model GCLF-EoS).
Los coeficientes de ELV se estimaron por el metodo UNIFAC, que se basa en las contribuciones de los diversos grupos que configuran las moleculas de una solucion.
Since Electrolyte NRTL did not support molecules estimated by UNIFAC, catechol was present in a quantity equal to all monomers identified, less phenol and guaiacol.
Las deducciones de estas ecuaciones, en el caso de soluciones solvente-electrolito, son generalmente teorico-experimentales; en donde el aporte teorico proviene generalmente de la ley de fuerzas intermoleculares, en las cuales se tiene en cuenta la combinacion de las fuerzas electrostaticas de largo alcance, donde generalmente se utiliza la teoria de Debye-Huckel; con las interacciones de corto alcance; en la cual se manejan modelos de actividad convencionales como UNIFAC (Kikic et al., 1991), UNIQUAC (Macedo et al., 1990), NRTL (Chen et al., 1986) y Wilson (Zhao et al., 2000), que han sido modificados permanentemente para su uso en soluciones electroliticas.
The project involves the study of multiphasic enzyme reactions using calculations of the thermodynamic properties of the reaction solutions with UNIFAC methods.