Hybrid supported zirconocene and niobocene catalysts on MAO-modified silicas

Santos, João Henrique Zimnoch dos; Gerbase, Annelise Engel; Rodenbusch, Karen Cristina; Pires, Gilvan Pozzobon; Martinelli, Márcia; Bichinho, Kátia M.

doi:10.1016/s1381-1169(01)00356-9

Cited by 29 publications

(13 citation statements)

References 27 publications

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“…In situ polymerization using a hybrid catalyst is a useful method for preparing LPE/BPE blend polymers. Desired structures of polyethylene can be achieved by optimizing the various catalyst properties 3–9…”

Section: Introductionmentioning

confidence: 99%

Uniform, Axial‐Orientation Alignment of One‐Dimensional Single‐Crystal Silicon Nanostructure Arrays

et al. 2005

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Section: Introductionmentioning

confidence: 99%

Uniform, Axial‐Orientation Alignment of One‐Dimensional Single‐Crystal Silicon Nanostructure Arrays

et al. 2005

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“…Extensive research has been published on ethylene polymerization with multi-site Ziegler catalysts and multiple single site catalysts comprising blends of different metallocenes, half-sandwich metallocenes, and Ziegler catalysts. [9][10][11][12][13][14][15][16][17] Much less is known concerning multi-site catalysts based upon post-metallocene catalysts, which have been employed to achieve reactor blends and polyethylenes with controlled polyethylene branching. [10,[18][19][20][21][22] Also different support materials were blended together in order to generate different catalytically active sites producing polyethylenes with different chain length.…”

Section: Introductionmentioning

confidence: 99%

Mesoporous Silica Supported Multiple Single‐Site Catalysts and Polyethylene Reactor Blends with Tailor‐Made Trimodal and Ultra‐Broad Molecular Weight Distributions

Kurek

Mark

Enders

et al. 2010

Macromol. Rapid Commun.

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A ternary blend of the bisiminopyridine chromium (III) (Cr-1) with the bisiminopyridine iron (II) (Fe-2) post-metallocenes with the quinolylsilylcyclopentadienyl chromium (III) halfsandwich complex (Cr-3) was supported on mesoporous silica to produce novel multiple single-site catalysts and polyethylene reactor blends with tailor-made molecular weight distributions (MWDs). The preferred cosupporting sequence of this ternary blend on MAO-treated silica was Fe-2 followed by Cr-1 and Cr-3. Cosupporting does not impair the single-site nature of the blend components producing polyethylene fractions with $\overline M _{\rm w}$ = 10(4) g · mol(-1) on Cr-1, $\overline M _{\rm w}$ = 3 × 10(5) g · mol(-1) on Fe-2, and $\overline M _{\rm w}$ = 3 × 10(6) g · mol(-1) on Cr-3. As a function of the Fe-2/Cr-1/Cr-2 mixing ratio it is possible to control the weight ratio of these three polyethylenes without affecting the individual average molecular weights and narrow polydispersities of the three polyethylene fractions. Tailor-made polyethylene reactor blends with ultra-broad MWD and polydispersities varying between 10 and 420 were obtained. When the molar ratio of Fe-2/Cr-1 was constant, the ultra-high molecular polyethylene (UHMWPE, $\overline M _{\rm w}$ > 10(6) g · mol(-1) ) content was varied between 8 and 16 wt.-% as a function of the Cr-3 content without impairing the blend ratio of the other two polyethylene fractions and without sacrificing melt processability. When the molar ratio Fe-2/Cr-3 was constant, it was possible to selectively increase the content of the low molecular weight fraction by additional cosupporting of Cr-1. Due to the intimate mixing of low and ultra-high molecular weight polyethylenes (UHMPEs) produced on cosupported single-site catalysts a wide range of melt processable polyethylene reactor blends was obtained.

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“…This result is attributed to the better accessibility of monomer units to the active sites or, as suggested by Greco et al, to the presence of more evenly spaced active catalytic species. These MAO modified silicas showed somewhat higher activities than other supported systems and required the addition of less external MAO ([Al] : [Zr] = 500) than other supported metallocenes, which frequently require [Al] : [Zr] = 1000–3000 to give effective concentrations of the active zirconocenium cations . However, comparisons between the performances of individual catalysts should be made with caution, as polymerization conditions are seldom standardized.…”

Section: Resultsmentioning

confidence: 99%

Characterization of MAO‐Modified Silicas for Ethylene Polymerization

Mortazavi

Ahmadjo

Santos

et al. 2013

J of Applied Polymer Sci

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A series of methylaluminoxane (MAO)-modified PQ and EP 12 silicas, calcined at 110, 250, and 450 C, were prepared.The resulting MAO-modified supports were characterized by a set of complementary techniques: Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), small angle X-ray scattering (SAXS), and thermal gravimetric analysis (TGA). The Al/Si ratios of the MAO-modified PQ and EP12 silicas were in the ranges of 0.19-0.27 wt % and 0.17-0.30 wt %, respectively. MAO-modified silicas were used in the polymerization of ethylene using an Et 2 IndZrCl 2 catalyst. The MAO-modified PQ silica showed higher activity in comparison to the MAO-modified EP12.

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Hybrid supported zirconocene and niobocene catalysts on MAO-modified silicas

Cited by 29 publications

References 27 publications

Uniform, Axial‐Orientation Alignment of One‐Dimensional Single‐Crystal Silicon Nanostructure Arrays

Uniform, Axial‐Orientation Alignment of One‐Dimensional Single‐Crystal Silicon Nanostructure Arrays

Mesoporous Silica Supported Multiple Single‐Site Catalysts and Polyethylene Reactor Blends with Tailor‐Made Trimodal and Ultra‐Broad Molecular Weight Distributions

Characterization of MAO‐Modified Silicas for Ethylene Polymerization

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