Documents disponibles écrits par cet auteur

Conversion of methane and carbon dioxide to higher value products / Vesna Havran in Industrial & engineering chemistry research, Vol. 50 N° 12 (Juin 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 12 (Juin 2011) . - pp. 7089-7100 Titre : Conversion of methane and carbon dioxide to higher value products Type de document : texte imprimé Auteurs : Vesna Havran, Auteur ; Milorad P. Dudukovic, Auteur ; Cynthia S. Lo, Auteur Année de publication : 2011 Article en page(s) : pp. 7089-7100 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Carbon  dioxide Résumé : In this manuscript we address the efforts reported in the literature on direct conversion of methane and carbon dioxide into higher value products. The abundance of these two greenhouse gases makes them potentially useful for chemical syntheses. However, strong intramolecular bonds render both molecules chemically inert and thermodynamically stable. Thus, significant energy inputs as well as properly designed catalytic systems are required for their reactions. In addition to traditional catalytic processes, new alternative routes-such as photocatalytic conversion and dielectric barrier discharges—have been suggested. Figures of merit for comparison of various approaches have not yet been reported and are overdue. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24239022 [article] Conversion of methane and carbon dioxide to higher value products [texte imprimé] / Vesna Havran, Auteur ; Milorad P. Dudukovic, Auteur ; Cynthia S. Lo, Auteur . - 2011 . - pp. 7089-7100. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 12 (Juin 2011) . - pp. 7089-7100 Mots-clés : Carbon  dioxide Résumé : In this manuscript we address the efforts reported in the literature on direct conversion of methane and carbon dioxide into higher value products. The abundance of these two greenhouse gases makes them potentially useful for chemical syntheses. However, strong intramolecular bonds render both molecules chemically inert and thermodynamically stable. Thus, significant energy inputs as well as properly designed catalytic systems are required for their reactions. In addition to traditional catalytic processes, new alternative routes-such as photocatalytic conversion and dielectric barrier discharges—have been suggested. Figures of merit for comparison of various approaches have not yet been reported and are overdue. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24239022

Effect of oxygen on cyclohexane oxidation / Radmila Jevtic in Industrial & engineering chemistry research, Vol. 48 N° 17 (Septembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7986–7993 Titre : Effect of oxygen on cyclohexane oxidation : a stirred tank study Type de document : texte imprimé Auteurs : Radmila Jevtic, Auteur ; P. A. Ramachandran, Auteur ; Milorad P. Dudukovic, Auteur Année de publication : 2009 Article en page(s) : pp. 7986–7993 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Cyclohexane  oxidation  Nylon-6  Nylon-6,6  Oxygen  availability Résumé : Cyclohexane oxidation is the first step in the currently used technology for production of Nylon-6 and Nylon-6,6 which employs a two-stage process. In the first stage, cyclohexane is oxidized with air to 4−8% conversion at about 80% selectivity to cyclohexanol and cyclohexanone as desired products. In this study, we examined the effect of oxygen availability on the volumetric productivity, yield, and selectivity of this reaction by using a stirred autoclave operated free from mass transfer effects in a batch and “dead-end” semibatch mode. Both uncatalyzed and catalyzed systems were used. The experimental and the modeling results lead to the conclusion that increased oxygen availability improves the productivity and selectivity at the fixed cyclohexane conversion (4%) as the residence time required declines with the increase in oxygen concentration. The positive effect on the reaction rate of increased oxygen concentration is the same when such an increase is achieved at constant pressure by raising the mole fraction of oxygen in the feed or by raising the total pressure in the system at fixed oxygen mole fraction. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900093q [article] Effect of oxygen on cyclohexane oxidation : a stirred tank study [texte imprimé] / Radmila Jevtic, Auteur ; P. A. Ramachandran, Auteur ; Milorad P. Dudukovic, Auteur . - 2009 . - pp. 7986–7993. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7986–7993 Mots-clés : Cyclohexane  oxidation  Nylon-6  Nylon-6,6  Oxygen  availability Résumé : Cyclohexane oxidation is the first step in the currently used technology for production of Nylon-6 and Nylon-6,6 which employs a two-stage process. In the first stage, cyclohexane is oxidized with air to 4−8% conversion at about 80% selectivity to cyclohexanol and cyclohexanone as desired products. In this study, we examined the effect of oxygen availability on the volumetric productivity, yield, and selectivity of this reaction by using a stirred autoclave operated free from mass transfer effects in a batch and “dead-end” semibatch mode. Both uncatalyzed and catalyzed systems were used. The experimental and the modeling results lead to the conclusion that increased oxygen availability improves the productivity and selectivity at the fixed cyclohexane conversion (4%) as the residence time required declines with the increase in oxygen concentration. The positive effect on the reaction rate of increased oxygen concentration is the same when such an increase is achieved at constant pressure by raising the mole fraction of oxygen in the feed or by raising the total pressure in the system at fixed oxygen mole fraction. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900093q

Gas holdup in gas — liquid stirred tanks / Sean G. Mueller in Industrial & engineering chemistry research, Vol. 49 N° 21 (Novembre 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 21 (Novembre 2010) . - pp. 10744-10750 Titre : Gas holdup in gas — liquid stirred tanks Type de document : texte imprimé Auteurs : Sean G. Mueller, Auteur ; Milorad P. Dudukovic, Auteur Année de publication : 2011 Article en page(s) : pp. 10744-10750 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Stirred  vessel  Hydrodynamics  Gas  holdup Résumé : A single-point optical probe is developed that can accurately obtain local gas holdup in a gas-liquid stirred tank across a wide range of operating pressures, temperatures, and fluids. It is found that the probe orientation to the flow in a stirred tank can cause underestimations in gas holdup if only a single probe orientation is used. The probe is also able to capture the complex flow pattern in the vessel. This allows improved understanding of optical probes and stirred tanks and generation of data at elevated pressure and temperature conditions needed for development of new fundamental models. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=23447967 [article] Gas holdup in gas — liquid stirred tanks [texte imprimé] / Sean G. Mueller, Auteur ; Milorad P. Dudukovic, Auteur . - 2011 . - pp. 10744-10750. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 21 (Novembre 2010) . - pp. 10744-10750 Mots-clés : Stirred  vessel  Hydrodynamics  Gas  holdup Résumé : A single-point optical probe is developed that can accurately obtain local gas holdup in a gas-liquid stirred tank across a wide range of operating pressures, temperatures, and fluids. It is found that the probe orientation to the flow in a stirred tank can cause underestimations in gas holdup if only a single probe orientation is used. The probe is also able to capture the complex flow pattern in the vessel. This allows improved understanding of optical probes and stirred tanks and generation of data at elevated pressure and temperature conditions needed for development of new fundamental models. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=23447967

On the gradient diffusion hypothesis and passive scalar transport in turbulent flows / Daniel P. Combest in Industrial & engineering chemistry research, Vol. 50 N° 15 (Août 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 15 (Août 2011) . - pp. 8817–8823 Titre : On the gradient diffusion hypothesis and passive scalar transport in turbulent flows Type de document : texte imprimé Auteurs : Daniel P. Combest, Auteur ; Palghat A. Ramachandran, Auteur ; Milorad P. Dudukovic, Auteur Année de publication : 2011 Article en page(s) : pp. 8817–8823 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Turbulent  flow  Transport  process  Diffusion Résumé : A discussion of modeling passive scalar transport in turbulent flows is given. Several methods employed to dose the scalar-flux term 〈u'φ'〉 that arises during Reynolds averaging are provided. Alternatives and improvements to the gradient diffusion hypotheses are addressed, most notably, the need for an alternative to the global constant turbulent Schmidt and Prandtl numbers. The reader is given a brief history covering methods used to predict turbulent Schmidt and Prandtl numbers, along with recommendations for future research, based partially on studies by Professor Stuart Churchill. More detailed formulations of turbulent Schmidt or Prandtl numbers will enable better approximations of the influence of turbulence in models of passive scalar flows using the gradient diffusion hypothesis. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24395827 [article] On the gradient diffusion hypothesis and passive scalar transport in turbulent flows [texte imprimé] / Daniel P. Combest, Auteur ; Palghat A. Ramachandran, Auteur ; Milorad P. Dudukovic, Auteur . - 2011 . - pp. 8817–8823. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 15 (Août 2011) . - pp. 8817–8823 Mots-clés : Turbulent  flow  Transport  process  Diffusion Résumé : A discussion of modeling passive scalar transport in turbulent flows is given. Several methods employed to dose the scalar-flux term 〈u'φ'〉 that arises during Reynolds averaging are provided. Alternatives and improvements to the gradient diffusion hypotheses are addressed, most notably, the need for an alternative to the global constant turbulent Schmidt and Prandtl numbers. The reader is given a brief history covering methods used to predict turbulent Schmidt and Prandtl numbers, along with recommendations for future research, based partially on studies by Professor Stuart Churchill. More detailed formulations of turbulent Schmidt or Prandtl numbers will enable better approximations of the influence of turbulence in models of passive scalar flows using the gradient diffusion hypothesis. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24395827