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Aqueous solubility of some natural phenolic compounds / Fatima L. Mota in Industrial & engineering chemistry research, Vol. 47 n°15 (Août 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 n°15 (Août 2008) . - p. 5182–5189 Titre : Aqueous solubility of some natural phenolic compounds Type de document : texte imprimé Auteurs : Fatima L. Mota, Auteur ; António J. Queimada, Auteur ; Simao P. Pinho, Auteur ; Eugénia A. Macedo, Auteur Année de publication : 2008 Article en page(s) : p. 5182–5189 Note générale : Bibliogr. p. 5188-5189 Langues : Anglais (eng) Mots-clés : Hydroxybenzoic  acids;  Phenylpropenoic  acids;  Shake-flask  method Résumé : In this work, the aqueous solubilities of two hydroxybenzoic acids (gallic and salicylic acid) and three phenylpropenoic acids (trans-cinnamic, ferulic, and caffeic acids) are addressed. Measurements were performed, as a function of temperature, between 288.15 and 323.15 K, using the shake-flask method for generating the saturated aqueous solutions, followed by compositional analysis by spectrophotometric and gravimetric methods. The pH values of the saturated aqueous solutions were measured by potentiometry. Additional thermodynamic properties, which are fundamental for a better understanding of the solubilization process, as well as necessary for the modeling studies, such as melting temperatures and fusion enthalpies were determined by differential scanning calorimetry (DSC). Apparent acid dissociation constants (Ka) were obtained by potentiometry titration. The measured data were modeled with the cubic-plus-association (CPA) equation of state (EoS). This EoS is applied, for the first time, for multifunctional associating molecules, and the results indicate that it can adequately be used to represent the measured and other literature data with satisfactory accuracy. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071452o [article] Aqueous solubility of some natural phenolic compounds [texte imprimé] / Fatima L. Mota, Auteur ; António J. Queimada, Auteur ; Simao P. Pinho, Auteur ; Eugénia A. Macedo, Auteur . - 2008 . - p. 5182–5189. Bibliogr. p. 5188-5189 Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 n°15 (Août 2008) . - p. 5182–5189 Mots-clés : Hydroxybenzoic  acids;  Phenylpropenoic  acids;  Shake-flask  method Résumé : In this work, the aqueous solubilities of two hydroxybenzoic acids (gallic and salicylic acid) and three phenylpropenoic acids (trans-cinnamic, ferulic, and caffeic acids) are addressed. Measurements were performed, as a function of temperature, between 288.15 and 323.15 K, using the shake-flask method for generating the saturated aqueous solutions, followed by compositional analysis by spectrophotometric and gravimetric methods. The pH values of the saturated aqueous solutions were measured by potentiometry. Additional thermodynamic properties, which are fundamental for a better understanding of the solubilization process, as well as necessary for the modeling studies, such as melting temperatures and fusion enthalpies were determined by differential scanning calorimetry (DSC). Apparent acid dissociation constants (Ka) were obtained by potentiometry titration. The measured data were modeled with the cubic-plus-association (CPA) equation of state (EoS). This EoS is applied, for the first time, for multifunctional associating molecules, and the results indicate that it can adequately be used to represent the measured and other literature data with satisfactory accuracy. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071452o

Modeling of biodiesel multicomponent systems with the cubic-plus-association (CPA) equation of state / Mariana B. Oliveira in Industrial & engineering chemistry research, Vol. 49 N° 3 (Fevrier 2010)

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 3 (Fevrier 2010) . - pp. 1419–1427 Titre : Modeling of biodiesel multicomponent systems with the cubic-plus-association (CPA) equation of state Type de document : texte imprimé Auteurs : Mariana B. Oliveira, Auteur ; António J. Queimada, Auteur ; João A.P. Coutinho, Auteur Année de publication : 2010 Article en page(s) : pp. 1419–1427 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Modeling--Biodiesel--Multicomponent--Systems--Cubic-Plus-Association--(CPA)  Equation--State Résumé : To supply biodiesel with the quality levels required by the standards for alternative fuels, the separation and purification units are extremely important in the biodiesel production plants. The correct knowledge and description of the phase equilibria in systems composed by transesterification products is essential for a correct operation and optimization of the purification process. For that purpose, the cubic-plus-association equation of state (CPA EoS) was here applied to model the phase equilibria of multicomponent systems common to biodiesel production and purification processes. It is shown that the CPA EoS can provide a good description of the liquid−liquid equilibria of multicomponent mixtures containing alcohols, glycerol, and fatty acid esters in the temperature range of operation of the separation units in biodiesel plants. As the liquid−liquid phase equilibrium description depends on the EoS parameters, a discussion is also presented about the best set of parameters and the method to estimate them. ISSN : 0888-5885 [article] Modeling of biodiesel multicomponent systems with the cubic-plus-association (CPA) equation of state [texte imprimé] / Mariana B. Oliveira, Auteur ; António J. Queimada, Auteur ; João A.P. Coutinho, Auteur . - 2010 . - pp. 1419–1427. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 3 (Fevrier 2010) . - pp. 1419–1427 Mots-clés : Modeling--Biodiesel--Multicomponent--Systems--Cubic-Plus-Association--(CPA)  Equation--State Résumé : To supply biodiesel with the quality levels required by the standards for alternative fuels, the separation and purification units are extremely important in the biodiesel production plants. The correct knowledge and description of the phase equilibria in systems composed by transesterification products is essential for a correct operation and optimization of the purification process. For that purpose, the cubic-plus-association equation of state (CPA EoS) was here applied to model the phase equilibria of multicomponent systems common to biodiesel production and purification processes. It is shown that the CPA EoS can provide a good description of the liquid−liquid equilibria of multicomponent mixtures containing alcohols, glycerol, and fatty acid esters in the temperature range of operation of the separation units in biodiesel plants. As the liquid−liquid phase equilibrium description depends on the EoS parameters, a discussion is also presented about the best set of parameters and the method to estimate them. ISSN : 0888-5885

Phase equilibria of ester + alcohol systems and their description with the cubic-plus-association equation of state / Mariana B. Oliveira in Industrial & engineering chemistry research, Vol. 49 N° 7 (Avril 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 7 (Avril 2010) . - pp. 3452–3458 Titre : Phase equilibria of ester + alcohol systems and their description with the cubic-plus-association equation of state Type de document : texte imprimé Auteurs : Mariana B. Oliveira, Auteur ; Sofia I. Miguel, Auteur ; António J. Queimada, Auteur Année de publication : 2010 Article en page(s) : pp. 3452–3458 Note générale : Industrial Chemistry Langues : Anglais (eng) Mots-clés : Equilibria  Ester  Alcohol  Cubic-Plus Résumé : The knowledge and the capability to describe the phase equilibria of binary systems formed by a fatty acid ester and an alcohol are of great interest in biodiesel production, where these mixtures can be found after the transesterification unit and where they must be separated to purify the biodiesel stream and to recover the unreacted alcohol. Despite this interest, little information is available on the vapor−liquid equilibria (VLE) of fatty acid ester + alcohol systems. To overcome this lack of data, new VLE measurements of six ester + methanol/ethanol systems were carried at atmospheric pressure. This new experimental data was successfully modeled with the Cubic-Plus-Association equation of state (CPA EoS), with global average deviations of 0.5% for the bubble-point temperatures. In all cases small and temperature independent parameters were enough to adequately describe the measured data. Furthermore a constant value for the cross-association energy parameter was proposed for each alcohol system, as well as a linear correlation for the binary interaction parameter with the ester chain length, making the CPA EoS a powerful predictive model for these systems. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901470s [article] Phase equilibria of ester + alcohol systems and their description with the cubic-plus-association equation of state [texte imprimé] / Mariana B. Oliveira, Auteur ; Sofia I. Miguel, Auteur ; António J. Queimada, Auteur . - 2010 . - pp. 3452–3458. Industrial Chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 7 (Avril 2010) . - pp. 3452–3458 Mots-clés : Equilibria  Ester  Alcohol  Cubic-Plus Résumé : The knowledge and the capability to describe the phase equilibria of binary systems formed by a fatty acid ester and an alcohol are of great interest in biodiesel production, where these mixtures can be found after the transesterification unit and where they must be separated to purify the biodiesel stream and to recover the unreacted alcohol. Despite this interest, little information is available on the vapor−liquid equilibria (VLE) of fatty acid ester + alcohol systems. To overcome this lack of data, new VLE measurements of six ester + methanol/ethanol systems were carried at atmospheric pressure. This new experimental data was successfully modeled with the Cubic-Plus-Association equation of state (CPA EoS), with global average deviations of 0.5% for the bubble-point temperatures. In all cases small and temperature independent parameters were enough to adequately describe the measured data. Furthermore a constant value for the cross-association energy parameter was proposed for each alcohol system, as well as a linear correlation for the binary interaction parameter with the ester chain length, making the CPA EoS a powerful predictive model for these systems. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901470s