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]  inIndustrial & 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

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