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Abstract: The spherical MgCl2 supports treated by methylaluminoxane (named MAO-supports) were prepared using MgCl2·2.56C2H5OH adducts as support material subjected to elimination of EtOH by thermal dealcoholization treatments. Then bis(phenoxy-imine) zirconium complex, bis-[N-(3-tert-butylsalicylidence)cyclohexylaminato] zirconium(IV) dichloride (1), was directly impregnated onto these MAO-supports. ICP, EDX, GC, N2-BET, IR and XRD analyses indicated that the texture of the supports and MAO-supports, the elements on solid catalysts, and so on, were greatly relied on dealcoholization temperature. Meanwhile, it was also found that the activities of the supported catalysts for ethylene polymerization and the properties of resultant polymers were strongly dependent on dealcoholization temperature. Finally, PEs with spherical morphology and high bulk density (over 0.35g/ml) were obtained, without reactor fouling. [Copyright &y& Elsevier]

Abstract: Trialkylaluminums as cocatalysts for bis(phenoxy-imine)Zr complexes, bis[N-(3-tert-butylsalicylidene)-anilinato]zirconium dichloride (1) and bis[N-(3-tert-butylsalicylidene)-cyclohexylaminato]zirconium dichloride (2), are investigated for ethylene polymerization without MAO or Ph3CB(C6F5)4. The effects of alkylaluminums, Al/Zr molar ratio, polymerization temperature and time as well as the comonomer 1-hexene on polymerization performance are examined. In appropriate range of Al/Zr molar ratio, the catalyst system bis(phenoxy-imine)Zr complex/trialkylaluminum shows high activity for ethylene polymerization, which approximates to bis(phenoxy-imine)Zr complex/MAO system. Their catalytic activities depend on not only the nature, but also the amount, of the trialkylaluminum. Both the molecular weights and the polydispersities (M w/M n) of PEs produced by 1 with Et3Al, He3Al, or Me3Al are higher than those with MAO. The nature, rather than the amount, of alkylaluminum determines the M w and the polydispersity of polymer in polymerization with the same complex. Unexpectedly, M w of the polyethylenes produced with complex 1/triethylaluminum increases with polymerization time. The catalyst system bis(phenoxy-imine)Zr complex/trialkylaluminum has low capacity of copolymerization. [Copyright &y& Elsevier]

Abstract: Different alkylaluminums (triethyl-, tri-iso-butyl-, n-trihexylaluminum) were tested as activator for the iron complex LFeCl2 (1) (L=2,6-bis[(2,4,6-trimethylphenylimino)ethyl]pyridine) in ethylene polymerization. Various polymerization temperatures and the molar ratios of Al/Fe prepared polyethylene (PE) with different molecular weights, molecular weight distributions, polymerization activities and polyethylene structures. Through the analysis of in situ UV–vis absorption spectra, ethylene polymerization results and prepared polyethylene structures, the distinctive behaviors of the catalytic system could result from a new applicable mechanism involving two different kinds of catalytic species LFeRCl (a) and LFeR2 (b) (R=Et, i-Bu or He), the ratio of which varied with changing Al/Fe mole ratio when alkylaluminums were used as activators. The catalytic species (a) with very high activity mainly produced linear PE with high molecular weight in the bimodal PE. The catalytic species (b) with low activity mainly produced branched PE of low molecular weight in the bimodal PE. [Copyright &y& Elsevier]