Documents disponibles écrits par cet auteur

Computer-aided solvent design for reactions / Milica Folic 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. 5190–5202 Titre : Computer-aided solvent design for reactions : maximizing product formation Type de document : texte imprimé Auteurs : Milica Folic, Auteur ; Adjiman, Claire S., Auteur ; Efstratios N. Pistikopoulos, Auteur Année de publication : 2008 Article en page(s) : p. 5190–5202 Note générale : Bibliogr. p. 5201-5202 Langues : Anglais (eng) Mots-clés : Computer-aided  methodology;  Solvents;  Complex  reaction  systems Résumé : A hybrid experimental/computer-aided methodology for the design of solvents for reactions, recently proposed by the authors [Folić et al., AIChE J. 2007, 53, 1240–1256], is extended. The methodology is based on the use of a few reaction rate measurements to build a reaction model, followed by the formulation and solution of an optimal computer-aided molecular design (CAMD) problem. The treatment of complex reaction systems, such as competing or consecutive reactions, is considered through the incorporation of a simple reactor model in the problem formulation. This approach is applied to two model reaction schemes, and it is shown that, in principle, it is possible to identify solvents that maximize product formation by enhancing the main reaction and suppressing byproduct formation. Since very few measurements are used to build the reaction model, the effect of uncertainty is tackled explicitly in a stochastic formulation of the CAMD problem. An approach to sensitivity analysis for the identification of the key model parameters is discussed. Using this information to generate scenarios, a stochastic optimization problem (whose objective is to determine the solvents with the best expected performance) is then solved. The final output consists of a list of candidate solvents that can be targeted for experimentation. The methodology is demonstrated on a Menschutkin reaction, which is a representative SN2 reaction. This shows that the uncertainty in the reaction model has little impact on the types of solvent molecules that have the best performance. Dinitrates are found to be a promising class of solvents, with regard to maximizing the reaction rate constant. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie0714549 [article] Computer-aided solvent design for reactions : maximizing product formation [texte imprimé] / Milica Folic, Auteur ; Adjiman, Claire S., Auteur ; Efstratios N. Pistikopoulos, Auteur . - 2008 . - p. 5190–5202. Bibliogr. p. 5201-5202 Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 n°15 (Août 2008) . - p. 5190–5202 Mots-clés : Computer-aided  methodology;  Solvents;  Complex  reaction  systems Résumé : A hybrid experimental/computer-aided methodology for the design of solvents for reactions, recently proposed by the authors [Folić et al., AIChE J. 2007, 53, 1240–1256], is extended. The methodology is based on the use of a few reaction rate measurements to build a reaction model, followed by the formulation and solution of an optimal computer-aided molecular design (CAMD) problem. The treatment of complex reaction systems, such as competing or consecutive reactions, is considered through the incorporation of a simple reactor model in the problem formulation. This approach is applied to two model reaction schemes, and it is shown that, in principle, it is possible to identify solvents that maximize product formation by enhancing the main reaction and suppressing byproduct formation. Since very few measurements are used to build the reaction model, the effect of uncertainty is tackled explicitly in a stochastic formulation of the CAMD problem. An approach to sensitivity analysis for the identification of the key model parameters is discussed. Using this information to generate scenarios, a stochastic optimization problem (whose objective is to determine the solvents with the best expected performance) is then solved. The final output consists of a list of candidate solvents that can be targeted for experimentation. The methodology is demonstrated on a Menschutkin reaction, which is a representative SN2 reaction. This shows that the uncertainty in the reaction model has little impact on the types of solvent molecules that have the best performance. Dinitrates are found to be a promising class of solvents, with regard to maximizing the reaction rate constant. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie0714549

Microstructural modeling of solid oxide fuel cell anodes / Joshua Golbert in Industrial & engineering chemistry research, Vol. 47 N°20 (Octobre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N°20 (Octobre 2008) . - P. 7693-7699 Titre : Microstructural modeling of solid oxide fuel cell anodes Type de document : texte imprimé Auteurs : Joshua Golbert, Auteur ; Adjiman, Claire S., Auteur ; Nigel P. Brandon, Auteur Année de publication : 2008 Article en page(s) : P. 7693-7699 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Solid  Oxide  Fuel  Cell  (SOFC)  Electrodes  SOFC Résumé : The design and manufacture of electrodes for use in SOFCs is one of the greatest challenges to the commercialization of fuel cell technology. Composite SOFC electrodes mix three phases (ion conducting, electron conducting, pore phase) in order to improve performance by increasing the amount of triple-phase boundaries (TBPs)—meetings of the ionic and electronic pathways with the percolating gas network—where the redox reaction takes place. The electrode microstructure is critical since electrode performance is directly dependent on the abundance of TPBs and the transport properties of the three phases.A fundamental understanding of the quantitative effects of microstructure on electrode performance is required. However, electrode models commonly neglect heterogeneity and assume effective values for key parameters. In contrast, we present a computational framework that can readily be linked to experimental studies of microstructure, thereby providing crucial insight into the conditions and competing processes in the porous microstructure, insight that can be used to design future generations of electrodes. In the proposed methodology, a virtual electrode is generated by randomly placing spherical particles in a packed bed. The particles are then expanded to simulate sintering to ensure large contact surfaces between the different phases. Once the porous structure is obtained, we can analyze the porosity and percolation of the various phases and the amount of triple-phase boundary and its percolation throughout the electrode. Furthermore, the transport and redox phenomena are also modeled to determine the potential, current, and chemical distribution throughout the different phases. We are then able to predict electrode performance based on fundamental properties of the underlying microstructure. These results are used to relate microstructural properties to electrode performance. The microstructural properties can include porosity, particle radii, and radius ratio and the effect of graded electrodes. The method is tested on model systems and used to demonstrate the effect of particle size on performance. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800065w [article] Microstructural modeling of solid oxide fuel cell anodes [texte imprimé] / Joshua Golbert, Auteur ; Adjiman, Claire S., Auteur ; Nigel P. Brandon, Auteur . - 2008 . - P. 7693-7699. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N°20 (Octobre 2008) . - P. 7693-7699 Mots-clés : Solid  Oxide  Fuel  Cell  (SOFC)  Electrodes  SOFC Résumé : The design and manufacture of electrodes for use in SOFCs is one of the greatest challenges to the commercialization of fuel cell technology. Composite SOFC electrodes mix three phases (ion conducting, electron conducting, pore phase) in order to improve performance by increasing the amount of triple-phase boundaries (TBPs)—meetings of the ionic and electronic pathways with the percolating gas network—where the redox reaction takes place. The electrode microstructure is critical since electrode performance is directly dependent on the abundance of TPBs and the transport properties of the three phases.A fundamental understanding of the quantitative effects of microstructure on electrode performance is required. However, electrode models commonly neglect heterogeneity and assume effective values for key parameters. In contrast, we present a computational framework that can readily be linked to experimental studies of microstructure, thereby providing crucial insight into the conditions and competing processes in the porous microstructure, insight that can be used to design future generations of electrodes. In the proposed methodology, a virtual electrode is generated by randomly placing spherical particles in a packed bed. The particles are then expanded to simulate sintering to ensure large contact surfaces between the different phases. Once the porous structure is obtained, we can analyze the porosity and percolation of the various phases and the amount of triple-phase boundary and its percolation throughout the electrode. Furthermore, the transport and redox phenomena are also modeled to determine the potential, current, and chemical distribution throughout the different phases. We are then able to predict electrode performance based on fundamental properties of the underlying microstructure. These results are used to relate microstructural properties to electrode performance. The microstructural properties can include porosity, particle radii, and radius ratio and the effect of graded electrodes. The method is tested on model systems and used to demonstrate the effect of particle size on performance. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800065w

Quantitative framework for reliable safety analysis / Huang, Haitao in Aiche journal, Vol. 48 N°1 (Janvier 2002) 

Public ISBD [article]  in Aiche journal > Vol. 48 N°1 (Janvier 2002) . - 78-96 p. Titre : Quantitative framework for reliable safety analysis Titre original : Travail Quantitatif d'Armature pour l'Analyse Fiable de Sûreté Type de document : texte imprimé Auteurs : Huang, Haitao, Auteur ; Adjiman, Claire S., Auteur ; Shah, Nilay Article en page(s) : 78-96 p. Note générale : Génie Chimique Langues : Anglais (eng) Mots-clés : Méthodologie  Processus  chimique  Risques  Sciences  économiques  Conservateur  Dynamique  non  linéaire  Armature  Simulation  Transition  Prolongation  Formalisme  Réacteur  Paramètre  Analyse Index. décimale : 660.627.3 Résumé : The effectiveness of any methodology used to identify hazards in chemical processes affects both safety and economics. To achieve maximum safety at minimum cost, a conservative, but realistic, analysis must be carried out. An approach to hazard identification is proposed based on a detailed process model which includes nonlinear dynamics and uncertainty. A new modeling framework, the region-transition model (RTM), is developed, which enables the simulation of regions of the operating space through an extension of the hybrid state transition system formalism. The RTM is illustrated on a nonlinear batch reactor with parameter uncertainty. A safety-verification algorithm identifies regions of the input space (initial conditions and external inputs) which guarantee safe operation. The algorithm is successfully applied to three examples: a tank with overflow and underflow, a batch reactor with an exothermic reaction, and a CSTR with feed preheating. L'efficacité de n'importe quelle méthodologie employée pour identifier des risques dans des processus chimiques affecte la sûreté et les sciences économiques. Pour réaliser la sûreté maximum au coût minimum, un conservateur, mais un réaliste, analyse doit être effectué. On propose une approche pour mettre en danger l'identification a basé sur un modèle de processus détaillé qui inclut la dynamique et l'incertitude non-linéaires. Un nouveau travail modelant d'armature, le modèle de transition de région (RTM), est développé, qui permet la simulation des régions de l'espace de fonctionnement par une prolongation du formalisme hybride de système de transition d'état. Le RTM est illustré sur un réacteur non-linéaire en lots avec l'incertitude de paramètre. Un algorithme de sûreté-vérification identifie des régions des dans l'espace mis (les conditions et externe initiaux met dedans) qui garantissent l'exploitation sûre. L'algorithme est avec succès appliqué à trois exemples : un réservoir avec l'écoulement d'excédent et sous l'écoulement, un réacteur en lots avec une réaction exothermique, et un CSTR avec le préchauffage d'alimentation. DEWEY : 660.627.3 ISSN : 0001-1541 En ligne : www.aiche.org [article] Quantitative framework for reliable safety analysis = Travail Quantitatif d'Armature pour l'Analyse Fiable de Sûreté [texte imprimé] / Huang, Haitao, Auteur ; Adjiman, Claire S., Auteur ; Shah, Nilay . - 78-96 p. Génie Chimique Langues : Anglais (eng) in Aiche journal > Vol. 48 N°1 (Janvier 2002) . - 78-96 p. Mots-clés : Méthodologie  Processus  chimique  Risques  Sciences  économiques  Conservateur  Dynamique  non  linéaire  Armature  Simulation  Transition  Prolongation  Formalisme  Réacteur  Paramètre  Analyse Index. décimale : 660.627.3 Résumé : The effectiveness of any methodology used to identify hazards in chemical processes affects both safety and economics. To achieve maximum safety at minimum cost, a conservative, but realistic, analysis must be carried out. An approach to hazard identification is proposed based on a detailed process model which includes nonlinear dynamics and uncertainty. A new modeling framework, the region-transition model (RTM), is developed, which enables the simulation of regions of the operating space through an extension of the hybrid state transition system formalism. The RTM is illustrated on a nonlinear batch reactor with parameter uncertainty. A safety-verification algorithm identifies regions of the input space (initial conditions and external inputs) which guarantee safe operation. The algorithm is successfully applied to three examples: a tank with overflow and underflow, a batch reactor with an exothermic reaction, and a CSTR with feed preheating. L'efficacité de n'importe quelle méthodologie employée pour identifier des risques dans des processus chimiques affecte la sûreté et les sciences économiques. Pour réaliser la sûreté maximum au coût minimum, un conservateur, mais un réaliste, analyse doit être effectué. On propose une approche pour mettre en danger l'identification a basé sur un modèle de processus détaillé qui inclut la dynamique et l'incertitude non-linéaires. Un nouveau travail modelant d'armature, le modèle de transition de région (RTM), est développé, qui permet la simulation des régions de l'espace de fonctionnement par une prolongation du formalisme hybride de système de transition d'état. Le RTM est illustré sur un réacteur non-linéaire en lots avec l'incertitude de paramètre. Un algorithme de sûreté-vérification identifie des régions des dans l'espace mis (les conditions et externe initiaux met dedans) qui garantissent l'exploitation sûre. L'algorithme est avec succès appliqué à trois exemples : un réservoir avec l'écoulement d'excédent et sous l'écoulement, un réacteur en lots avec une réaction exothermique, et un CSTR avec le préchauffage d'alimentation. DEWEY : 660.627.3 ISSN : 0001-1541 En ligne : www.aiche.org