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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: 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]

Hollow polyethylene spheres were achieved from solution-based ɑ-diimine nickel catalyst system with morphological controllable one-step synthesis. • Homogenous ɑ- diimine nickel complexes often produce bulk viscous polyethylene. • Spherical hollow polyethylene produced by coordination dispersion polymerization. • Tri-nuclear nickel complex show high activity for ethylene polymerization. In this paper, ɑ-diimine nickel catalyst without immobilization was successfully used for one-step synthesis of spherical hollow polyethylene particles at mild condition (1.0 MPa, 25 °C) by conducting coordination dispersion polymerization. It was found 2-methyl-2-pentanol (MP) played a key role in the formation of the unusual hollow particular morphology. By varying the addition amount of MP, changing the bulky groups of alkyl aluminum, and adjusting the concentration of nickel catalyst, the particle size was finely tuned. A plausible mechanism was proposed to interpret the formation of these polyethylene hollow particles. [ABSTRACT FROM AUTHOR]