Documents disponibles écrits par cet auteur

Oxidation of chloride ion on platinum electrode / Rajkumar S. Patil in Industrial & engineering chemistry research, Vol. 50 N° 23 (Décembre 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 23 (Décembre 2011) . - pp. 12946–12959 Titre : Oxidation of chloride ion on platinum electrode : dynamics of electrode passivation and its effect on oxidation kinetics Type de document : texte imprimé Auteurs : Rajkumar S. Patil, Auteur ; Vinay A. Juvekar, Auteur ; Vijay M. Naik, Auteur Année de publication : 2012 Article en page(s) : pp. 12946–12959 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Oxidation  Ion  Kinetics Résumé : Kinetics of oxidation of chloride ion is studied on both active platinum electrode and that undergoing transient passivation. Experiments are conducted in concentrated NaCl solution at rotating disk electrode. It is observed that on the active platinum electrode, oxidation is very fast, and hence the current density is controlled by the ohmic resistance of the solution. Electrode kinetics becomes important only when the electrode is passivated to a significant extent. Kinetics of chloride oxidation on the electrode undergoing passivation is modeled using the Butler–Volmer equation, in which the contribution from the ohmic resistance of the solution is incorporated. Two regimes of passivation are identified. The first is the fast regime corresponding to the formation of the platinum oxide monolayer. In this regime, the rate of passivation is first order in the concentration of the metal sites on the surface. In the slow passivation regime, the exchange current density for chloride oxidation is found to vary inversely with square root of time. This regime is modeled by considering unsteady diffusion of oxygen ions through the metal lattice. From this analysis it is concluded that the chloride oxidation current is almost totally contributed by a small fraction of the active metal sites which are continuously being regenerated as a result of diffusion of oxygen ions from the surface into the bulk of the metal. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie200663a [article] Oxidation of chloride ion on platinum electrode : dynamics of electrode passivation and its effect on oxidation kinetics [texte imprimé] / Rajkumar S. Patil, Auteur ; Vinay A. Juvekar, Auteur ; Vijay M. Naik, Auteur . - 2012 . - pp. 12946–12959. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 23 (Décembre 2011) . - pp. 12946–12959 Mots-clés : Oxidation  Ion  Kinetics Résumé : Kinetics of oxidation of chloride ion is studied on both active platinum electrode and that undergoing transient passivation. Experiments are conducted in concentrated NaCl solution at rotating disk electrode. It is observed that on the active platinum electrode, oxidation is very fast, and hence the current density is controlled by the ohmic resistance of the solution. Electrode kinetics becomes important only when the electrode is passivated to a significant extent. Kinetics of chloride oxidation on the electrode undergoing passivation is modeled using the Butler–Volmer equation, in which the contribution from the ohmic resistance of the solution is incorporated. Two regimes of passivation are identified. The first is the fast regime corresponding to the formation of the platinum oxide monolayer. In this regime, the rate of passivation is first order in the concentration of the metal sites on the surface. In the slow passivation regime, the exchange current density for chloride oxidation is found to vary inversely with square root of time. This regime is modeled by considering unsteady diffusion of oxygen ions through the metal lattice. From this analysis it is concluded that the chloride oxidation current is almost totally contributed by a small fraction of the active metal sites which are continuously being regenerated as a result of diffusion of oxygen ions from the surface into the bulk of the metal. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie200663a

Self-similar dynamics of a flexible ring polymer in a fixed obstacle environment / Balaji V. S. Iyer in Industrial & engineering chemistry research, Vol. 48 N° 21 (Novembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9514–9522 Titre : Self-similar dynamics of a flexible ring polymer in a fixed obstacle environment : a coarse-grained molecular model Type de document : texte imprimé Auteurs : Balaji V. S. Iyer, Auteur ; Ashish K. Lele, Auteur ; Vinay A. Juvekar, Auteur Année de publication : 2010 Article en page(s) : pp. 9514–9522 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Flexible  ring  polymers  Molecular  model Résumé : In this contribution we concern ourselves with an interesting problem, namely, the dynamics of ideal flexible ring polymers constrained in an array of fixed obstacles. The fundamental issue in this problem is to understand how a topologically constrained polymer chain is able to relax its conformation in the absence of chain ends. The key physics was provided in an elegant scaling theory by Rubinstein and co-workers (Obukhov, S. P.; Rubinstein, M.; Duke, T. Dynamics of a Ring Polymer in a Gel. Phys. Rev. Lett. 1994, 73, 1263−1267). In this work we develop a coarse-grained mean-field model based on the physical arguments of the scaling theory and derive constitutive relations for rings in fixed obstacle and melt environments. The model is composed of three distinct steps. In the first step the dynamics of an arbitrary section of a ring chain is worked out based on fractal Blob−Spring (BS) dynamics, and the center of mass diffusion and the relaxation spectrum of this section are determined. In the second step the center of mass diffusion obtained using the BS dynamics is used to model the one-dimensional diffusion of the section in a topologically constrained environment. In the final step we invoke the idea of dynamic self-similarity and argue that the dynamics described in the first and the second step, for any arbitrary section of the chain, applies to all sections of the chain. The constitutive relation is obtained consequently as the superposition of dynamic response of all sections of the ring chain. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900535v [article] Self-similar dynamics of a flexible ring polymer in a fixed obstacle environment : a coarse-grained molecular model [texte imprimé] / Balaji V. S. Iyer, Auteur ; Ashish K. Lele, Auteur ; Vinay A. Juvekar, Auteur . - 2010 . - pp. 9514–9522. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9514–9522 Mots-clés : Flexible  ring  polymers  Molecular  model Résumé : In this contribution we concern ourselves with an interesting problem, namely, the dynamics of ideal flexible ring polymers constrained in an array of fixed obstacles. The fundamental issue in this problem is to understand how a topologically constrained polymer chain is able to relax its conformation in the absence of chain ends. The key physics was provided in an elegant scaling theory by Rubinstein and co-workers (Obukhov, S. P.; Rubinstein, M.; Duke, T. Dynamics of a Ring Polymer in a Gel. Phys. Rev. Lett. 1994, 73, 1263−1267). In this work we develop a coarse-grained mean-field model based on the physical arguments of the scaling theory and derive constitutive relations for rings in fixed obstacle and melt environments. The model is composed of three distinct steps. In the first step the dynamics of an arbitrary section of a ring chain is worked out based on fractal Blob−Spring (BS) dynamics, and the center of mass diffusion and the relaxation spectrum of this section are determined. In the second step the center of mass diffusion obtained using the BS dynamics is used to model the one-dimensional diffusion of the section in a topologically constrained environment. In the final step we invoke the idea of dynamic self-similarity and argue that the dynamics described in the first and the second step, for any arbitrary section of the chain, applies to all sections of the chain. The constitutive relation is obtained consequently as the superposition of dynamic response of all sections of the ring chain. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900535v

Solid suspension and liquid phase mixing in solid−liquid stirred tanks / Madhavi V. Sardeshpande in Industrial & engineering chemistry research, Vol. 48 N° 21 (Novembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9713–9722 Titre : Solid suspension and liquid phase mixing in solid−liquid stirred tanks Type de document : texte imprimé Auteurs : Madhavi V. Sardeshpande, Auteur ; Aparna R. Sagi, Auteur ; Vinay A. Juvekar, Auteur Année de publication : 2010 Article en page(s) : pp. 9713–9722 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Stirred  tanks  Catalytic  reactions  Crystallization Résumé : Stirred tanks are widely used in chemical process industries for catalytic reactions, dissolution of solids, crystallization, and so on. In designing and optimizing such processes, suspension quality of slurry is an important parameter. Suspension quality depends upon complex interactions of impeller generated flow, turbulence, and solid loading. Most of the earlier work on solid suspension focuses on identifying critical impeller speed for just suspension of solids (Njs). In this study, apart from Njs, aspects like cloud height and liquid phase mixing in solid−liquid suspensions were also studied. A new way of characterizing solid−liquid suspensions and liquid phase mixing using nonintrusive wall pressure fluctuation measurements has been developed. Systematic experimental data on Njs, cloud height, power consumption, mixing time, and circulation time over a range of solid volume fraction and impeller speeds have been presented here. The results and discussion presented here will have useful implications for designing solid−liquid stirred tanks. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801858a [article] Solid suspension and liquid phase mixing in solid−liquid stirred tanks [texte imprimé] / Madhavi V. Sardeshpande, Auteur ; Aparna R. Sagi, Auteur ; Vinay A. Juvekar, Auteur . - 2010 . - pp. 9713–9722. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9713–9722 Mots-clés : Stirred  tanks  Catalytic  reactions  Crystallization Résumé : Stirred tanks are widely used in chemical process industries for catalytic reactions, dissolution of solids, crystallization, and so on. In designing and optimizing such processes, suspension quality of slurry is an important parameter. Suspension quality depends upon complex interactions of impeller generated flow, turbulence, and solid loading. Most of the earlier work on solid suspension focuses on identifying critical impeller speed for just suspension of solids (Njs). In this study, apart from Njs, aspects like cloud height and liquid phase mixing in solid−liquid suspensions were also studied. A new way of characterizing solid−liquid suspensions and liquid phase mixing using nonintrusive wall pressure fluctuation measurements has been developed. Systematic experimental data on Njs, cloud height, power consumption, mixing time, and circulation time over a range of solid volume fraction and impeller speeds have been presented here. The results and discussion presented here will have useful implications for designing solid−liquid stirred tanks. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801858a