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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

Investigation on the uniformity and stability of sunflower oil/water emulsions prepared by a shirasu porous glass membrane / Yueling Zhang in Industrial & engineering chemistry research, Vol. 47 N°17 (Septembre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N°17 (Septembre 2008) . - p. 6412–6417 Titre : Investigation on the uniformity and stability of sunflower oil/water emulsions prepared by a shirasu porous glass membrane Type de document : texte imprimé Auteurs : Yueling Zhang, Auteur ; Guoping Lian, Auteur ; Shiping Zhu, Auteur Année de publication : 2008 Article en page(s) : p. 6412–6417 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : SPG  membrane  emulsification  Sunflower  oil  emulsions Résumé : Shirasu porous glass (SPG) membrane emulsification has many advantages over traditional emulsification methods of stirring, ultrasoubd, and homogenization. The main advantages are much improved uniform size distribution of the droplets and lower mechanical shear stress. This paper examines the uniformity and stability of sunflower oil emulsions prepared by SPG membrane. The effects of emulsifiers on the uniformity and stability of emulsions were investigated. Results showed that emulsions stabilized by Tween 20 are generally more uniform and stable compared to those stabilized by Tween 60. Emulsions prepared by membrane emulsification showed excellent uniformity and stability with no droplet size change after 6-months storage, while those prepared by the homogenizer have a much broad size distribution and are unstable after 7 days of storage with significant further broadening of the droplet size distribution by coalescence and Oswald ripening. Uniform-sized sunflower O/W emulsions prepared by the SPG membrane also have good thermal stability when subjected to either freezing or heating. The mechanical stability of sunflower O/W emulsions prepared by the SPG membrane can be further improved by adding thickeners to the aqueous phase. Therefore, SPG membrane emulsification is a promising method for preparing uniform and stable emulsions, which will have good potential applications in the food industry, in terms of improving shelf life and product quality. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8002232 [article] Investigation on the uniformity and stability of sunflower oil/water emulsions prepared by a shirasu porous glass membrane [texte imprimé] / Yueling Zhang, Auteur ; Guoping Lian, Auteur ; Shiping Zhu, Auteur . - 2008 . - p. 6412–6417. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N°17 (Septembre 2008) . - p. 6412–6417 Mots-clés : SPG  membrane  emulsification  Sunflower  oil  emulsions Résumé : Shirasu porous glass (SPG) membrane emulsification has many advantages over traditional emulsification methods of stirring, ultrasoubd, and homogenization. The main advantages are much improved uniform size distribution of the droplets and lower mechanical shear stress. This paper examines the uniformity and stability of sunflower oil emulsions prepared by SPG membrane. The effects of emulsifiers on the uniformity and stability of emulsions were investigated. Results showed that emulsions stabilized by Tween 20 are generally more uniform and stable compared to those stabilized by Tween 60. Emulsions prepared by membrane emulsification showed excellent uniformity and stability with no droplet size change after 6-months storage, while those prepared by the homogenizer have a much broad size distribution and are unstable after 7 days of storage with significant further broadening of the droplet size distribution by coalescence and Oswald ripening. Uniform-sized sunflower O/W emulsions prepared by the SPG membrane also have good thermal stability when subjected to either freezing or heating. The mechanical stability of sunflower O/W emulsions prepared by the SPG membrane can be further improved by adding thickeners to the aqueous phase. Therefore, SPG membrane emulsification is a promising method for preparing uniform and stable emulsions, which will have good potential applications in the food industry, in terms of improving shelf life and product quality. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8002232