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Effect of catalysts supporting on tandem polymerization of ethylene stock in synthesis ofethylene-1-hexene copolymer / Junwei Zhang 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. 5369-5375 Titre : Effect of catalysts supporting on tandem polymerization of ethylene stock in synthesis ofethylene-1-hexene copolymer Type de document : texte imprimé Auteurs : Junwei Zhang, Auteur ; Hong Fan, Auteur ; Bo-Geng Li, Auteur ; Shiping Zhu, Auteur Année de publication : 2008 Article en page(s) : p. 5369-5375 Note générale : Bibliogr. p. 5374-5375 Langues : Anglais (eng) Mots-clés : Ethylene  stock;  Copolymérisation;  polyéthylène Résumé : Ethylene-1-hexene copolymers were synthesized with a tandem catalysis system consisting of a new trimerization catalyst (1), bis(2-dodecylsulfanylethyl)amine-CrCl3, and a copolymerization catalyst (2), Et(Ind)2ZrCl2. Catalysts 1 and 2 were supported on silica particles, and the effects of different supporting strategies on trimerization selectivity, 1-hexene incorporation efficiency, and copolymerization activity were studied and compared to the homogeneous system. It was found that the supported 1 trimerized ethylene with a similar selectivity (>99%) but one-quarter of the activity of the homogeneous 1. The supported 2 gave 40% 1-hexene incorporation efficiency and one-third of the copolymerization activity of the homogeneous 2. The tandem action of the supported 1 and 2 yielded linear low-density polyethylene (LLDPE) materials that contained only C4 side-chains. The dual supported system had activities at a 107 g/(mol Zr h) level, in the same order of the homogeneous counterpart. Adjusting the Cr/Zr ratio yielded various branching densities and, thus, melting temperatures of the resulting polymers. The samples prepared with the supported 2 exhibited broad differential scanning calorimetry (DSC) curves, probably due to multiple active sites. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie7017564 [article] Effect of catalysts supporting on tandem polymerization of ethylene stock in synthesis ofethylene-1-hexene copolymer [texte imprimé] / Junwei Zhang, Auteur ; Hong Fan, Auteur ; Bo-Geng Li, Auteur ; Shiping Zhu, Auteur . - 2008 . - p. 5369-5375. Bibliogr. p. 5374-5375 Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 n°15 (Août 2008) . - p. 5369-5375 Mots-clés : Ethylene  stock;  Copolymérisation;  polyéthylène Résumé : Ethylene-1-hexene copolymers were synthesized with a tandem catalysis system consisting of a new trimerization catalyst (1), bis(2-dodecylsulfanylethyl)amine-CrCl3, and a copolymerization catalyst (2), Et(Ind)2ZrCl2. Catalysts 1 and 2 were supported on silica particles, and the effects of different supporting strategies on trimerization selectivity, 1-hexene incorporation efficiency, and copolymerization activity were studied and compared to the homogeneous system. It was found that the supported 1 trimerized ethylene with a similar selectivity (>99%) but one-quarter of the activity of the homogeneous 1. The supported 2 gave 40% 1-hexene incorporation efficiency and one-third of the copolymerization activity of the homogeneous 2. The tandem action of the supported 1 and 2 yielded linear low-density polyethylene (LLDPE) materials that contained only C4 side-chains. The dual supported system had activities at a 107 g/(mol Zr h) level, in the same order of the homogeneous counterpart. Adjusting the Cr/Zr ratio yielded various branching densities and, thus, melting temperatures of the resulting polymers. The samples prepared with the supported 2 exhibited broad differential scanning calorimetry (DSC) curves, probably due to multiple active sites. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie7017564

Polypropylene and ethylene-propylene copolymer reactor alloys prepared by metallocene/ziegler-natta hybrid catalyst / Lie Lu in Industrial & engineering chemistry research, Vol. 48 N° 18 (Septembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 18 (Septembre 2009) . - pp. 8349–8355 Titre : Polypropylene and ethylene-propylene copolymer reactor alloys prepared by metallocene/ziegler-natta hybrid catalyst Type de document : texte imprimé Auteurs : Lie Lu, Auteur ; Hong Fan, Auteur ; Bo-Geng Li, Auteur Année de publication : 2010 Article en page(s) : pp. 8349–8355 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Polypropylene  Ethylene−propylene  rubber  reactor  Propylene  homopolymerization  Metallocene  activation  Ethylene−propylene  copolymerization Résumé : Polypropylene/ethylene−propylene rubber (PP/EPR) reactor alloys were prepared with a metallocene/Ziegler−Natta hybrid catalyst system (rac-Et(Ind)2ZrCl2/TiCl4/MgCl2) using a process composed of three stages: propylene homopolymerization, metallocene activation, and ethylene−propylene copolymerization. A series of alloy samples were produced and characterized at various copolymerization conditions by varying the methylaluminoxane (MAO)/Zr ratio and monomer composition. It was shown that the metallocene/Ziegler−Natta hybrid system exhibited the features of both metallocene and Ziegler−Natta catalysts during copolymerization. The hybrid catalyst had better ability in incorporating α-olefin than the Ziegler−Natta catalyst owing to the action of metallocene active sites. DSC and IR analyses suggested that EPR in the alloys became random with increased MAO/Zr ratio. In addition, reducing the ethylene content in the feed decreased the activity and promoted the production of random copolymers. An operation window of reaction conditions was identified for the preparation of well-dispersed spherical PP/EPR reactor alloy particles containing up to about 40 wt % EPR. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900579h [article] Polypropylene and ethylene-propylene copolymer reactor alloys prepared by metallocene/ziegler-natta hybrid catalyst [texte imprimé] / Lie Lu, Auteur ; Hong Fan, Auteur ; Bo-Geng Li, Auteur . - 2010 . - pp. 8349–8355. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 18 (Septembre 2009) . - pp. 8349–8355 Mots-clés : Polypropylene  Ethylene−propylene  rubber  reactor  Propylene  homopolymerization  Metallocene  activation  Ethylene−propylene  copolymerization Résumé : Polypropylene/ethylene−propylene rubber (PP/EPR) reactor alloys were prepared with a metallocene/Ziegler−Natta hybrid catalyst system (rac-Et(Ind)2ZrCl2/TiCl4/MgCl2) using a process composed of three stages: propylene homopolymerization, metallocene activation, and ethylene−propylene copolymerization. A series of alloy samples were produced and characterized at various copolymerization conditions by varying the methylaluminoxane (MAO)/Zr ratio and monomer composition. It was shown that the metallocene/Ziegler−Natta hybrid system exhibited the features of both metallocene and Ziegler−Natta catalysts during copolymerization. The hybrid catalyst had better ability in incorporating α-olefin than the Ziegler−Natta catalyst owing to the action of metallocene active sites. DSC and IR analyses suggested that EPR in the alloys became random with increased MAO/Zr ratio. In addition, reducing the ethylene content in the feed decreased the activity and promoted the production of random copolymers. An operation window of reaction conditions was identified for the preparation of well-dispersed spherical PP/EPR reactor alloy particles containing up to about 40 wt % EPR. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900579h