Documents disponibles écrits par cet auteur

Experimental errors in kinetic tests and its influence on the precision of estimated parameters. Part I, Analysis of first-order reactions / André L. Alberton in Chemical engineering journal, Vol. 155 N° 3 (Decembre 2009) 

Public ISBD [article]  in Chemical engineering journal > Vol. 155 N° 3 (Decembre 2009) . - pp. 816-823 Titre : Experimental errors in kinetic tests and its influence on the precision of estimated parameters. Part I, Analysis of first-order reactions Type de document : texte imprimé Auteurs : André L. Alberton, Auteur ; Marcio Schwaab, Auteur ; Martin Schmal, Auteur Année de publication : 2010 Article en page(s) : pp. 816-823 Note générale : Génie Chimique Langues : Anglais (eng) Mots-clés : Experimental  error  Kinetic  analysis  First-order  reaction  Precise  parameter  estimation Index. décimale : 660 Résumé : The proper characterization of the experimental errors is essential for the correct evaluation of estimated model parameters, model fit and model predictions based on kinetic rate expressions. However, it is common to ignore the influence of experimental errors during kinetic studies due to difficulties to characterize how experimental errors depend on the reaction conditions. The behavior of experimental error depends on the specific features of the experimental system; however, in many cases the main sources of experimental errors are the unavoidable oscillations of the input variables. This work analyzes how the experimental errors affect kinetic studies based on catalytic tests when oscillations of the input variables are the main sources of uncertainties. The first part of this work assumes that the reaction rate can be described accurately as a first-order reaction in a PFR. Analytical expressions are derived for the variance of the reactant conversion in distinct scenarios and are used to analyze the quality of the obtained parameter estimates. It is shown here that the conversion variances can be described as functions of the measured conversion values, normally presenting a point of maximum for conversion values in the range of 0.6 < X < 1.0 when observed experimental fluctuations are controlled by the fluctuations of the input variables. Constant conversion variances should be expected only when fluctuations are controlled by analytical conversion measurements. As a consequence, optimum parameter estimation may be performed either with differential or integral methods, depending on the behavior of the conversion variances. DEWEY : 660 ISSN : 1385-8947 En ligne : http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFJ-4X24VV2-4&_user=6 [...] [article] Experimental errors in kinetic tests and its influence on the precision of estimated parameters. Part I, Analysis of first-order reactions [texte imprimé] / André L. Alberton, Auteur ; Marcio Schwaab, Auteur ; Martin Schmal, Auteur . - 2010 . - pp. 816-823. Génie Chimique Langues : Anglais (eng) in Chemical engineering journal > Vol. 155 N° 3 (Decembre 2009) . - pp. 816-823 Mots-clés : Experimental  error  Kinetic  analysis  First-order  reaction  Precise  parameter  estimation Index. décimale : 660 Résumé : The proper characterization of the experimental errors is essential for the correct evaluation of estimated model parameters, model fit and model predictions based on kinetic rate expressions. However, it is common to ignore the influence of experimental errors during kinetic studies due to difficulties to characterize how experimental errors depend on the reaction conditions. The behavior of experimental error depends on the specific features of the experimental system; however, in many cases the main sources of experimental errors are the unavoidable oscillations of the input variables. This work analyzes how the experimental errors affect kinetic studies based on catalytic tests when oscillations of the input variables are the main sources of uncertainties. The first part of this work assumes that the reaction rate can be described accurately as a first-order reaction in a PFR. Analytical expressions are derived for the variance of the reactant conversion in distinct scenarios and are used to analyze the quality of the obtained parameter estimates. It is shown here that the conversion variances can be described as functions of the measured conversion values, normally presenting a point of maximum for conversion values in the range of 0.6 < X < 1.0 when observed experimental fluctuations are controlled by the fluctuations of the input variables. Constant conversion variances should be expected only when fluctuations are controlled by analytical conversion measurements. As a consequence, optimum parameter estimation may be performed either with differential or integral methods, depending on the behavior of the conversion variances. DEWEY : 660 ISSN : 1385-8947 En ligne : http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFJ-4X24VV2-4&_user=6 [...]

Hybrid modeling of methane reformers. 3 / André L. Alberton in Industrial & engineering chemistry research, Vol. 48 N° 23 (Décembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 23 (Décembre 2009) . - pp. 10277–10283 Titre : Hybrid modeling of methane reformers. 3 : optimal geometries of perforated catalyst pellets Type de document : texte imprimé Auteurs : André L. Alberton, Auteur ; Marcio Schwaab, Auteur ; Roberto Carlos Bittencourt, Auteur Année de publication : 2010 Article en page(s) : pp. 10277–10283 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Hybrid--Modeling--Methane--Reformers--Optimal--Geometries--Perforated--Catalyst  Pellets Résumé : This paper studies the optimization of catalyst pellet geometries for the simultaneous maximization of the mechanical strength and catalyst activity of perforated catalyst pellets used for the reforming of methane. This multiobjective problem can be analyzed with the help of Pareto fronts. A previous work (Part 1: Alberton; et al. Ind. Eng. Chem. Res., in press) demonstrated that the effectiveness factor of catalysts with complex geometry used for the reforming of methane can be expressed as a linear function of the specific area of the pellet; consequently, catalyst activity can be expressed in terms of the geometric parameters of the pellet. It can also be assumed that the mechanical strength of perforated catalyst pellets is related to the minimum wall thickness of the solid piece. Therefore, two optimization problems can be proposed: (i) the simultaneous maximization of the specific area and of the minimum wall thickness of the pellet and (ii) the simultaneous maximization of the overall catalyst activity in the catalyst bed and of the minimum wall thickness of the pellet. These objective functions are evaluated here for several catalyst geometries and analyzed with a Pareto filter. The Pareto fronts obtained for the two analyzed cases are essentially the same, indicating that the maximization of the specific area constitutes a useful criterion for design of perforated catalysts in diffusion-controlled systems. Optimized catalyst geometries are presented for different catalyst designs and can be used as references for future manufacture of catalyst pellets. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9001662 [article] Hybrid modeling of methane reformers. 3 : optimal geometries of perforated catalyst pellets [texte imprimé] / André L. Alberton, Auteur ; Marcio Schwaab, Auteur ; Roberto Carlos Bittencourt, Auteur . - 2010 . - pp. 10277–10283. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 23 (Décembre 2009) . - pp. 10277–10283 Mots-clés : Hybrid--Modeling--Methane--Reformers--Optimal--Geometries--Perforated--Catalyst  Pellets Résumé : This paper studies the optimization of catalyst pellet geometries for the simultaneous maximization of the mechanical strength and catalyst activity of perforated catalyst pellets used for the reforming of methane. This multiobjective problem can be analyzed with the help of Pareto fronts. A previous work (Part 1: Alberton; et al. Ind. Eng. Chem. Res., in press) demonstrated that the effectiveness factor of catalysts with complex geometry used for the reforming of methane can be expressed as a linear function of the specific area of the pellet; consequently, catalyst activity can be expressed in terms of the geometric parameters of the pellet. It can also be assumed that the mechanical strength of perforated catalyst pellets is related to the minimum wall thickness of the solid piece. Therefore, two optimization problems can be proposed: (i) the simultaneous maximization of the specific area and of the minimum wall thickness of the pellet and (ii) the simultaneous maximization of the overall catalyst activity in the catalyst bed and of the minimum wall thickness of the pellet. These objective functions are evaluated here for several catalyst geometries and analyzed with a Pareto filter. The Pareto fronts obtained for the two analyzed cases are essentially the same, indicating that the maximization of the specific area constitutes a useful criterion for design of perforated catalysts in diffusion-controlled systems. Optimized catalyst geometries are presented for different catalyst designs and can be used as references for future manufacture of catalyst pellets. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9001662

Kinetics of toluene disproportionation / Marcos W. N. Lobao in Industrial & engineering chemistry research, Vol. 51 N° 1 (Janvier 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 1 (Janvier 2012) . - pp. 171–183 Titre : Kinetics of toluene disproportionation : Modeling and experiments Type de document : texte imprimé Auteurs : Marcos W. N. Lobao, Auteur ; André L. Alberton, Auteur ; Silvio A. B. V. Melo, Auteur Année de publication : 2012 Article en page(s) : pp. 171–183 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Kinetics  Modeling Résumé : This work presents modeling and experimental studies on the kinetics of toluene disproportionation in operation ranges that include real industrial operation conditions. The influence of reaction temperature, reactor pressure, feed composition, and residence time on conversion of reactants and product selectivity was investigated. Experiments were performed according to a sequential experimental design strategy, in order to provide maximum accuracy for model predictions. Statistical treatment of parameter estimates and model adequacy was performed with the help of maximum likelihood principles. Excellent agreement between model predictions and available experimental data was obtained in the full ranges of investigated experimental conditions. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie2015526 [article] Kinetics of toluene disproportionation : Modeling and experiments [texte imprimé] / Marcos W. N. Lobao, Auteur ; André L. Alberton, Auteur ; Silvio A. B. V. Melo, Auteur . - 2012 . - pp. 171–183. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 1 (Janvier 2012) . - pp. 171–183 Mots-clés : Kinetics  Modeling Résumé : This work presents modeling and experimental studies on the kinetics of toluene disproportionation in operation ranges that include real industrial operation conditions. The influence of reaction temperature, reactor pressure, feed composition, and residence time on conversion of reactants and product selectivity was investigated. Experiments were performed according to a sequential experimental design strategy, in order to provide maximum accuracy for model predictions. Statistical treatment of parameter estimates and model adequacy was performed with the help of maximum likelihood principles. Excellent agreement between model predictions and available experimental data was obtained in the full ranges of investigated experimental conditions. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie2015526