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Kinetic analysis of oleic acid esterification using lipase as catalyst in a microaqueous environment / Mohd Sabri Mahmud 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. 1071–1078 Titre : Kinetic analysis of oleic acid esterification using lipase as catalyst in a microaqueous environment Type de document : texte imprimé Auteurs : Mohd Sabri Mahmud, Auteur ; Tomasz Safinski, Auteur ; Mark I. Nelson, Auteur Année de publication : 2010 Article en page(s) : pp. 1071–1078 Note générale : Industrial Chemistry Langues : Anglais (eng) Mots-clés : Analysis--Esterification--Oleic  Acid--Lipase--Microaqueous--Catalyst--Environment Résumé : This paper reports the lipase-catalyzed esterification of oleic acid (with ethanol) in a batch reactor at temperatures between 298 and 338 K using a wide range of the reactant ratio, β (0 < β < 2). All kinetic runs were performed under conditions of negligible transport limitations. The sigmoidal behavior evidenced from the initial rate−substrate concentration curve suggests the allosteric nature of the acrylic-supported Aspergillus lipase, and hence, the data were described by a non-Michaelis Menten kinetic model. The associated oleic acid binding coefficient and ethanol inhibition constant were obtained as 2.382 and 1.643 mmol L−1, respectively. The allosteric effect was attributed to conformational change in the enzyme site occasioned by the presence of trace amounts of water formed within the first few minutes of the reaction. Indeed, the transient water concentration profile at different β values revealed an initial overshoot in water concentration before the relaxation to final equilibrium value after about 6 h. The appearance of the initial overshoot increased with decreasing β. The water concentration history is symptomatic of two first-order interacting processes fed by a self-propagating input consistent with the two-enzyme state concerted symmetry proposition for nonlinear feedback autoregulatory behavior. The rate-temperature envelope showed a maximum at about 318 K, suggesting protein denaturation above this temperature. Even so, a fit of the rate data obtained between 298 to 318 K gave an activation energy of 22.4 kJ mol−1, typical of many enzymatic reactions. FTIR spectra of the catalysts displayed peaks at 1723.23 and 1666.12 cm−1 assigned to COO− and NH2+ groups, respectively, for both fresh and used specimens. BET measurements, however, revealed a significant drop in surface area between fresh (165 m2 g−1) and used (5−20 m2 g−1) catalysts. This was attributed to pore blockage of the immobilized enzyme by the relatively large oleic−acyl−lipase complex left after the reaction. Note de contenu : Bibiogr. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900704n [article] Kinetic analysis of oleic acid esterification using lipase as catalyst in a microaqueous environment [texte imprimé] / Mohd Sabri Mahmud, Auteur ; Tomasz Safinski, Auteur ; Mark I. Nelson, Auteur . - 2010 . - pp. 1071–1078. Industrial Chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 3 (Fevrier 2010) . - pp. 1071–1078 Mots-clés : Analysis--Esterification--Oleic  Acid--Lipase--Microaqueous--Catalyst--Environment Résumé : This paper reports the lipase-catalyzed esterification of oleic acid (with ethanol) in a batch reactor at temperatures between 298 and 338 K using a wide range of the reactant ratio, β (0 < β < 2). All kinetic runs were performed under conditions of negligible transport limitations. The sigmoidal behavior evidenced from the initial rate−substrate concentration curve suggests the allosteric nature of the acrylic-supported Aspergillus lipase, and hence, the data were described by a non-Michaelis Menten kinetic model. The associated oleic acid binding coefficient and ethanol inhibition constant were obtained as 2.382 and 1.643 mmol L−1, respectively. The allosteric effect was attributed to conformational change in the enzyme site occasioned by the presence of trace amounts of water formed within the first few minutes of the reaction. Indeed, the transient water concentration profile at different β values revealed an initial overshoot in water concentration before the relaxation to final equilibrium value after about 6 h. The appearance of the initial overshoot increased with decreasing β. The water concentration history is symptomatic of two first-order interacting processes fed by a self-propagating input consistent with the two-enzyme state concerted symmetry proposition for nonlinear feedback autoregulatory behavior. The rate-temperature envelope showed a maximum at about 318 K, suggesting protein denaturation above this temperature. Even so, a fit of the rate data obtained between 298 to 318 K gave an activation energy of 22.4 kJ mol−1, typical of many enzymatic reactions. FTIR spectra of the catalysts displayed peaks at 1723.23 and 1666.12 cm−1 assigned to COO− and NH2+ groups, respectively, for both fresh and used specimens. BET measurements, however, revealed a significant drop in surface area between fresh (165 m2 g−1) and used (5−20 m2 g−1) catalysts. This was attributed to pore blockage of the immobilized enzyme by the relatively large oleic−acyl−lipase complex left after the reaction. Note de contenu : Bibiogr. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900704n

Oxidative photomineralization of dichloroacetic acid in an externally-irradiated rectangular bubble tank reactor: computational fluid dynamics modeling and experimental verification studies / Francisco J. Trujillo in Industrial & engineering chemistry research, Vol. 49 N° 15 (Août 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 15 (Août 2010) . - pp 6722–6734 Titre : Oxidative photomineralization of dichloroacetic acid in an externally-irradiated rectangular bubble tank reactor: computational fluid dynamics modeling and experimental verification studies Type de document : texte imprimé Auteurs : Francisco J. Trujillo, Auteur ; Tomasz Safinski, Auteur ; Adesoji A. Adesina, Auteur Année de publication : 2010 Article en page(s) : pp 6722–6734 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Oxidative  photomineralization  Fluid  dynamics. Résumé : The effect of antecedent factors on the performance of an aerated tank photoreactor containing externally irradiated suspended titania particles has been carried out using the oxidative photomineralisation of dichloroacetic acid (DCA) as the model reaction. The phase hold-up contours, velocity distribution profiles, and the spatial variation of the incident radiative flux as well as the local volumetric rate of photon absorption (LVPRA) inside the reactor were obtained from computational fluid dynamics (CFD) simulation based on the simultaneous solution of the Navier−Stokes equation (NSE) and radiation transport equation (RTE). The species modeling equation (SME) for the oxidative decomposition of DCA to HCl and CO2 was then coupled to the NSE and RTE to determine the influence of catalyst loading, air superficial velocity, pollutant concentration, and radiation intensity on the reactor performance. The SME utilized the intrinsic kinetic expression provided by Zalazar et al. [Chem. Eng. Sci. 2005, 60, 5240−5254] with rate parameters secured from a preliminary fit of our experimental data. The good agreement between numerical results and empirical data for practically all predictor variables suggest that CFD modeling is a reliable and valid tool for the design and evaluation of the new photoreactor system and may in fact be used as a surrogate for subsequent optimization studies. Within the range of variables examined, it is evident that although reaction rate initially increased with air flow rate, a “plateau” was attained after about 30 L min−1. The rate also exhibited a maximum at a catalyst loading of about 2.5 g L−1 while a characteristic Langmuir-type dependency on DCA concentration was observed. However, reaction rate varied only linearly with light intensity indicating the absence of deleterious hole−electron recombination at the relatively low values (20−80 W m−2) employed. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901364z [article] Oxidative photomineralization of dichloroacetic acid in an externally-irradiated rectangular bubble tank reactor: computational fluid dynamics modeling and experimental verification studies [texte imprimé] / Francisco J. Trujillo, Auteur ; Tomasz Safinski, Auteur ; Adesoji A. Adesina, Auteur . - 2010 . - pp 6722–6734. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 15 (Août 2010) . - pp 6722–6734 Mots-clés : Oxidative  photomineralization  Fluid  dynamics. Résumé : The effect of antecedent factors on the performance of an aerated tank photoreactor containing externally irradiated suspended titania particles has been carried out using the oxidative photomineralisation of dichloroacetic acid (DCA) as the model reaction. The phase hold-up contours, velocity distribution profiles, and the spatial variation of the incident radiative flux as well as the local volumetric rate of photon absorption (LVPRA) inside the reactor were obtained from computational fluid dynamics (CFD) simulation based on the simultaneous solution of the Navier−Stokes equation (NSE) and radiation transport equation (RTE). The species modeling equation (SME) for the oxidative decomposition of DCA to HCl and CO2 was then coupled to the NSE and RTE to determine the influence of catalyst loading, air superficial velocity, pollutant concentration, and radiation intensity on the reactor performance. The SME utilized the intrinsic kinetic expression provided by Zalazar et al. [Chem. Eng. Sci. 2005, 60, 5240−5254] with rate parameters secured from a preliminary fit of our experimental data. The good agreement between numerical results and empirical data for practically all predictor variables suggest that CFD modeling is a reliable and valid tool for the design and evaluation of the new photoreactor system and may in fact be used as a surrogate for subsequent optimization studies. Within the range of variables examined, it is evident that although reaction rate initially increased with air flow rate, a “plateau” was attained after about 30 L min−1. The rate also exhibited a maximum at a catalyst loading of about 2.5 g L−1 while a characteristic Langmuir-type dependency on DCA concentration was observed. However, reaction rate varied only linearly with light intensity indicating the absence of deleterious hole−electron recombination at the relatively low values (20−80 W m−2) employed. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901364z