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Kinetic study on stereospecific polymerization of 1,3 - butadiene using a nickel based catalyst system in environmentally friendly solvent / Archana Singh in Industrial & engineering chemistry research, Vol. 51 N° 34 (Août 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 34 (Août 2012) Titre : Kinetic study on stereospecific polymerization of 1,3 - butadiene using a nickel based catalyst system in environmentally friendly solvent Type de document : texte imprimé Auteurs : Archana Singh, Auteur ; Ankur Chavda, Auteur ; Subrahmanyam Nandula, Auteur Année de publication : 2012 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Catalyst  Polymerization  Kinetics Résumé : The present work describes the stereospecific polymerization of 1,3-butadiene catalyzed by a nickel naphthenate/ triethylaluminum/boron trifluoride etherate catalytic system in a noncarcinogenic solvent mixture. The detailed study on the effect of various parameters on the polymerization and product characteristics is reported. The catalyst concentration and reaction temperature did not have any significant effect on microstructure. Moreover, the conversion was observed to be the maximum at a 1.07 boron trifluoride/alkylaluminum molar ratio. The effect of catalyst concentration showed that at lower concentrations, a lower number of active sites leads to higher molecular weight (Mw) while the polydispersity index (PDI) exhibited a reverse trend. The polymerization was first order with respect to monomer as well as catalyst concentration. The overall rate constant was found to be 0.032 s―1 mol―1 for this catalyst system. The activation energy of the polymerization was found to be 14.1 kcal mol―1. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26299430 [article] Kinetic study on stereospecific polymerization of 1,3 - butadiene using a nickel based catalyst system in environmentally friendly solvent [texte imprimé] / Archana Singh, Auteur ; Ankur Chavda, Auteur ; Subrahmanyam Nandula, Auteur . - 2012. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 34 (Août 2012) Mots-clés : Catalyst  Polymerization  Kinetics Résumé : The present work describes the stereospecific polymerization of 1,3-butadiene catalyzed by a nickel naphthenate/ triethylaluminum/boron trifluoride etherate catalytic system in a noncarcinogenic solvent mixture. The detailed study on the effect of various parameters on the polymerization and product characteristics is reported. The catalyst concentration and reaction temperature did not have any significant effect on microstructure. Moreover, the conversion was observed to be the maximum at a 1.07 boron trifluoride/alkylaluminum molar ratio. The effect of catalyst concentration showed that at lower concentrations, a lower number of active sites leads to higher molecular weight (Mw) while the polydispersity index (PDI) exhibited a reverse trend. The polymerization was first order with respect to monomer as well as catalyst concentration. The overall rate constant was found to be 0.032 s―1 mol―1 for this catalyst system. The activation energy of the polymerization was found to be 14.1 kcal mol―1. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26299430

Retarding effect of aromatic solvents on cobalt (II) - based catalyst system during synthesis of high cis - 1,4 - polybutadiene / Archana Singh in Industrial & engineering chemistry research, Vol. 49 N° 20 (Octobre 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 20 (Octobre 2010) . - pp. 9648–9654 Titre : Retarding effect of aromatic solvents on cobalt (II) - based catalyst system during synthesis of high cis - 1,4 - polybutadiene Type de document : texte imprimé Auteurs : Archana Singh, Auteur ; Siddharth Modi, Auteur ; N. Subrahmanyam, Auteur Année de publication : 2011 Article en page(s) : pp. 9648–9654 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Aromatic  solvents  Catalyst Résumé : The present study discloses the influence of aliphatic (cyclohexane) and aromatic solvents with different π-electron densities viz. toluene, o-xylene, ethylbenzene (EB), and p-diethylbenzene (PDEB) on the cobalt-catalyzed high cis-polymerization of 1,3-butadiene. Comparative study in cyclohexane and toluene has been conducted in view to understand the effect of solvent on catalyst reactivity, molecular weight of the polymer, and polymerization kinetics. At given reaction conditions conversion is highest (68%) in cyclohexane, followed by toluene (27%) and EB (8%). Respective polymerization rate constants are found to be 0.0170, 0.0020, and 0.0008 min−1. Higher viscosity average molecular weight (M) of polymer observed in toluene (M = 4.68 × 105) compared to that in cyclohexane (M = 2.37 × 105) indicates that the presence of lower number of active sites leads to higher molecular weight. Cyclohexane shows activity at a lower water:alkylaluminum ratio than does toluene; as the π-electron of toluene reduces the Lewis acidity of hydrolyzed diethylaluminum chloride (DEAC) more than cyclohexane, where influence of π-electron is absent. The effect of different solvents has also been demonstrated by respective shifting of wavelength (λ) of solvent π → π*, cobalt 4A2 → 4T1(P), as well as 4T1 g (F) → 4T1 g (P) and activated butadienyl π(HOMO) → π*(LUMO) transitions. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie101324d [article] Retarding effect of aromatic solvents on cobalt (II) - based catalyst system during synthesis of high cis - 1,4 - polybutadiene [texte imprimé] / Archana Singh, Auteur ; Siddharth Modi, Auteur ; N. Subrahmanyam, Auteur . - 2011 . - pp. 9648–9654. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 20 (Octobre 2010) . - pp. 9648–9654 Mots-clés : Aromatic  solvents  Catalyst Résumé : The present study discloses the influence of aliphatic (cyclohexane) and aromatic solvents with different π-electron densities viz. toluene, o-xylene, ethylbenzene (EB), and p-diethylbenzene (PDEB) on the cobalt-catalyzed high cis-polymerization of 1,3-butadiene. Comparative study in cyclohexane and toluene has been conducted in view to understand the effect of solvent on catalyst reactivity, molecular weight of the polymer, and polymerization kinetics. At given reaction conditions conversion is highest (68%) in cyclohexane, followed by toluene (27%) and EB (8%). Respective polymerization rate constants are found to be 0.0170, 0.0020, and 0.0008 min−1. Higher viscosity average molecular weight (M) of polymer observed in toluene (M = 4.68 × 105) compared to that in cyclohexane (M = 2.37 × 105) indicates that the presence of lower number of active sites leads to higher molecular weight. Cyclohexane shows activity at a lower water:alkylaluminum ratio than does toluene; as the π-electron of toluene reduces the Lewis acidity of hydrolyzed diethylaluminum chloride (DEAC) more than cyclohexane, where influence of π-electron is absent. The effect of different solvents has also been demonstrated by respective shifting of wavelength (λ) of solvent π → π*, cobalt 4A2 → 4T1(P), as well as 4T1 g (F) → 4T1 g (P) and activated butadienyl π(HOMO) → π*(LUMO) transitions. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie101324d