The effect of reaction parameters on catalytic activity in the polymerization of ethylene using supported and unsupported metallocene catalysts

Quijada, Raúl; Rojas, René S.; Narváez, Ana; Alzamora, Luis; Retuert, Jaime; Rabagliati, Franco M.

doi:10.1016/s0926-860x(97)00259-7

Cited by 23 publications

(9 citation statements)

References 15 publications

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“…Moreover, catalyst 1 produces propylene blocks at the same feed gas ratio (P:E 0.25) whereas 2 and 3 only show isolated propylene units. It has also been shown that ethylene propylene copolymerizations carried out with Et(Ind) 2 ZrCl 2 supported on silica gel [20,21] lead to similar copolymers as those from the homogeneous system. The observation that copolymers obtained from both catalyst 2 and 3 do not contain propylene blocks leads to the conclusion that the 4 atom bridge possibly produces a narrower bite angle and a more constrained geometry of the complex, resulting in a less favored propylene insertion with respect to ethylene.…”

Section: Ethylene-propylene Copolymerization: Comparison Of Catalyst mentioning

confidence: 97%

Video Microscopy for the Investigation of Gas Phase Copolymerization

Fink

2005

Macro Materials & Eng

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Summary: Video microscopy as a tool for investigating olefin gas phase copolymerization is presented for the first time in this paper. The central theme of this work is the study of the comonomer effect shown by an unbridged metallocene catalyst supported on silica. By using video microscopy, it is possible to observe the increase in catalytic activity in terms of particle growth as well as monomer consumption. The observation that a more pronounced induction period in the particle growth profile is shown with increasing propylene concentration led us to investigate the copolymers obtained at different polymerization times using 13C NMR analysis and single particle energy dispersive X‐ray (EDX mapping). This allowed us to adapt the “polymer growth and particle expansion model” to the copolymerization. Besides physical causes for the comonomer effect, we wanted to determine whether the catalyst structure plays an important role in the comonomer effect. To this end we investigated two metallocenes bearing the same long bridging unit but differing in the ligand bound to the zirconium center. One metallocene bears a cyclopentadienyl ring, while the other bears an indenyl group. From a close analysis of the 13C NMR, it is clear that both catalysts insert ethylene more easily then propylene, probably due to the long bridging unit that results in a narrower aperture angle of the ligand. In addition to this, the indenyl ligand does not allow the formation of propylene blocks even at high propylene concentration.

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Section: Ethylene-propylene Copolymerization: Comparison Of Catalyst mentioning

confidence: 97%

Video Microscopy for the Investigation of Gas Phase Copolymerization

Fink

2005

Macro Materials & Eng

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“…9 Bimodal molecular weight distribution ethylene-1-hexene copolymers were obtained with solid catalysts prepared from the combination of dibutylmagnesium, titanium dichloride, MAO and (nBuCp) 2 ZrCl 2 . 10 Ethylene-1-butene copolymers were also produced from MAO-modi®ed silica impregnated with (nBuCp) 2 ZrCl 2 , co-catalyzed by isoBu 3 Al.…”

Section: Introductionmentioning

confidence: 99%

Linear low-density polyethylene synthesis promoted by homogeneous and supported catalysts

et al. 1999

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“…The metallocenes have become an important class of catalysts for olefin polymerization, due to the possibility of modeling the molecular structure of the polymers [1]. In comparison with the conventional Ziegler-Natta catalysts, the metallocene-based systems offer a great versatility and flexibility in the synthesis and control of the polyolefin structure [2].…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, morphology studies of polymers obtained with metallocenes anchored in different supports [1,[15][16][17] indicated a direct relation between the polymer and support morphology.…”

Section: Introductionmentioning

confidence: 99%