Browsing by Author "Brignole, Esteban A."
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- Application of the GCA-EOS model to the supercritical processing of associating oil derivatives: fatty acids, alcohols and triglyceridesPublication . Ferreira, Olga; Pereda, Selva; Bottini, Susana B.; Brignole, Esteban A.Supercritical processes are of interest in the fatty oil industry for a variety of applications: extraction and refining, removal of pollutants, recovery of specialties, hydrogenation of oils and derivatives, etc. Typical process mixtures include heavy compounds and gases at near critical conditions. At high pressures these asymmetric systems present a complex multiphase behaviour, difficult to model. This complexity increases if some of the mixture components are able to self- and/or cross associate. In the present work, the group contribution with association equation of state (GCA-EoS) [3] is extended to represent high pressure phase equilibria in mixtures of supercritical gases (carbon dioxide, propane, ethane) with fatty oil derivatives, such as mono- and di-glycerides, fatty acids, alcohols, water and esters. Self- and cross association between associating groups present in these mixtures are considered. Satisfactory correlation and prediction of equilibrium data are obtained. The capacity of the model to follow the behaviour of solutions towards the limit of infinite dilution of the associating components is of particular importance.
- Application of the GCA-EoS model to the supercritical processing of fatty oil derivativesPublication . Ferreira, Olga; Macedo, Maria E.; Brignole, Esteban A.The group-contribution with association equation of state (GCA-EoS) is applied to represent high-pressure phase equilibria in mixtures of supercritical gases (carbon dioxide, propane) with fatty oil derivatives, such as mono- and di-glycerides, fatty acids and fatty acid esters. Association effects in these mixtures are described by a group-contribution approach using three different association groups: the hydroxyl group, the acid group and the ester group. Satisfactory predictions of vapor–liquid equilibria, liquid–liquid equilibria and c1 of binary and ternary mixtures of high-molecular weight triacyglycerides and their derivatives with carbon dioxide or propane are obtained. It is shown that the GCA-EoS is a powerful engineering tool for the design and optimization of extraction and fractionation processes of fatty oil derivatives with supercritical fluids.
- Extension of UNIFAC to associating systemsPublication . Foco, Gloria; Ferreira, Olga; Brignole, Esteban A.; Bottini, Susana B.An extended UNIFAC group contribution model for the prediction of activity coefficients in associating mixtures was presented recently (Mengarelli et al.,1999). In the present work the model is applied to solutions containing alcohols, water, carboxylic acids and inert components. The residual UNIFAC local composition term is re-parameterized in order to take into account only dispersive forces between associating and inert functional groups. Good representation of vapor-liquid and liquid-liquid equilibrium, as well as infinite dilution activity coefficients is achieved by using a single set of group interaction parameters.
- A general group contribution model for activity coefficients in associating solutionsPublication . Ferreira, Olga; Brignole, Esteban A.; Bottini, Susana B.; Macedo, Eugénia A.A modifed UNIFAC group contribution model for the prediction of activity coefficients in associating mixtures was proposed recently (Mengarelli et al., 1999). In the present work, the model is extended to carboxylic acids by defining a general associating group which allows a straightforward extension to multicomponent mixtures. The residual UNIFAC local composition term is re-parameterized in order to take into account only dispersive forces between associating and inert functional groups. Good correlation and prediction of experimental VLE, LLE and g∞ data for mixtures containing water, acids, alcohols and inert compounds are obtained.
- A group contribution model for activity coefficients in associating solutionsPublication . Ferreira, Olga; Brignole, Esteban A.; Bottini, Susana B.A group contribution model is presented for the prediction of activity coefficients in associating mixtures. The new model adds an association term to the traditional UNIFAC residual and combinatorial contributions to the activity coefficients. The association term is based on Wertheim’s theory for fluids with highly directed attractive forces, as applied in the SAFT equation, and it follows the group contribution approach proposed by Gros et al. in the GCA-EOS model. Good predictions of both, vaporliquid and liquid-liquid equilibria are achieved in the whole concentration range, with a single set of group interaction parameters.
- Modeling of association effects in mixtures of carboxylic acids with associating and non-associating componentsPublication . Ferreira, Olga; Fornari, Tiziana; Brignole, Esteban A.; Bottini, Susana B.The group contribution with association equation of state GCA-EOS has been applied to calculate thermodynamic properties of pure compounds and mixtures of carboxylic acids with paraffins, alcohols, water and gases, at low and high pressures. Two associating groups, OH and COOH, were defined. Self- and cross-association in these mixtures were quantified through two parallel COOH/COOH and OH/OH associations. The validity of this approach is supported by an excellent representation of pure compound properties (vapor pressures and compressibility factors) and phase equilibria in mixtures of (associating + inert) and (associating + associating) components at low and high pressures.
- Modelling of phase equilibria for associating mixtures using an equation of statePublication . Ferreira, Olga; Brignole, Esteban A.; Macedo, Maria E.In the present work, the group contribution with association equation of state (GCA-EoS) is extended to represent phase equilibria in mixtures containing acids, esters, and ketones, with water, alcohols, and any number of inert components. Association effects are represented by a group-contribution approach. Self- and cross-association between the associating groups present in these mixtures are considered. The GCA-EoS model is compared to the group-contribution method MHV2, which does not take into account explicitly association effects. The results obtained with the GCA-EoS model are, in general, more accurate when compared to the ones achieved by the MHV2 equation with less number of parameters. Model predictions are presented for binary self- and cross-associating mixtures.
- Phase equilibria in sugar solutions using the A-UNIFAC modelPublication . Ferreira, Olga; Brignole, Esteban A.; Macedo, Maria E.In this work, a modified UNIFAC model that explicitly takes into account association effects is used to describe the thermodynamic properties of phase equilibria of mixtures containing common sugars, alcohols, and water. Three main groups were defined to represent the sugars family: the sugar ring (pyranose and furanose), the osidic bond (-O-), and the hydroxyl ring group (OHring). For the association term, a general two-site OH associating group is used to represent association effects in these solutions, allowing a straightforward extension to multicomponent mixtures. Correlation of both solvent properties (osmotic coefficients, water activities, vapor pressures, and boiling and freezing points of binary aqueous sugar solutions) and sugar solubility in water and alcohols gives very accurate results. Good predictions are obtained for vapor-liquid equilibrium and solid-liquid equilibrium of ternary and quaternary mixtures of sugars in mixed solvents.
- The extended gca-eos model for mixtures of fatty oils and derivativesPublication . Ferreira, Olga; Fornari, Tiziana; Brignole, Esteban A.; Bottini, Susana B.The Group Contribution Equation of State GC-EOS has been satisfactory applied to the modeling of high-pressure phase equilibria of supercritical gases (CO2, propane, ethane, dimethylether) with pure triglycerides and natural vegetable oils. The GC-EOS model size-related parameter, i.e. the critical hard sphere diameter, of the high molecular weight compounds were determined by fitting infinite dilution activity coefficients of n-alkanes in these heavy compounds. In this way the GC-EOS model was able to correlate and predict vapor-liquid (VLE) and liquid-liquid (LLE) equilibria of these mixtures, using a unique set of parameters, in good agreement with experimental data. In this work the application of the model is extended to mixtures containing fatty oil derivatives, such as fatty acids, fatty acids esters, mono - and diglycerides. The associating effects between molecules are described using an upgraded version of the model, the Group Contribution Associating - EOS. Satisfactory correlation and prediction of experimental VLE, LLE and ginfinite data in binary and ternary mixtures of these products with supercritical gases are obtained.