Characterization of MAO-modified silicas

Bianchini, Daniela; Santos, João Henrique Zimnoch dos; Uozumi, Toshiya; Sano, Tsuneji

doi:10.1016/s1381-1169(02)00047-x

Cited by 32 publications

(34 citation statements)

References 28 publications

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“…By increasing the Al amount other Al species are clearly observed, indicating an increase in the amount of the species responsible for the absorption at 286 nm. It is worth mentioning that two Al species were also observed by X-ray photoelectron spectroscopy (XPS) in the case of MAO-modified silica for this same Al content [9]. In Fig.…”

Section: Resultsmentioning

confidence: 64%

“…Vibrational modes corresponding to Cp groups might be covered by the large band centered at 3400 cm −1 . It is worth mentioning that DRIFTS monitoring of MAO-modified silica has shown after 10.0 wt.% Al/SiO 2 no residual silanol groups remained on silica surface [9].…”

Section: Resultsmentioning

confidence: 92%

“…In another work [8], we studied the effect of several experimental parameters on the immobilization of metallocene on silica, determining optimal preparative conditions for immobilization of (nBuCp) 2 ZrCl 2 onto silica Grace 948. Silica modified with MAO in different contents was characterized by a series of complementary techniques [9]. Taking into account these previous results, we decided to study the effect of silica surface MAO coverage on zirconocene loading, on catalyst activity and on polymer properties.…”

Section: Introductionmentioning

confidence: 99%

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Effect of MAO silica surface loading on (nBuCp)2ZrCl2 anchoring, on catalyst activity and on polymer properties

Bianchini

Stedile

Santos

2004

Applied Catalysis A: General

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Section: Resultsmentioning

confidence: 64%

Section: Resultsmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

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Effect of MAO silica surface loading on (nBuCp)2ZrCl2 anchoring, on catalyst activity and on polymer properties

Bianchini

Stedile

Santos

2004

Applied Catalysis A: General

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“…Preparation of SiO 2 /MAO (4 wt.-% Al/SiO 2 ) [10] MAO-modified silica was prepared by impregnating 1.0 g of thermally-treated silica Grace 948 with an MAO-toluene solution corresponding to 4 wt.-% Al/SiO 2 , at room temperature for 3 h under stirring. The solvent was removed under vacuum and the solid was dried.…”

Section: Methodsmentioning

confidence: 99%

Tandem Action of Tp^MsNiCl and Supported Cp₂ZrCl₂ Catalysts for the Production of Linear Low‐Density Polyethylene

Kuhn¹,

Silva²,

Casagrande³

et al. 2006

Macro Chemistry & Physics

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Summary: Linear low‐density polyethylene (LLDPE) samples with different properties were prepared from ethylene, without the addition of an α‐olefin co‐monomer, using a combination of the catalyst precursors TpMsNiCl (TpMs = hydridotris(3‐mesitylpyrazol‐1‐yl) and Cp2ZrCl2/SMAO‐4, by varying the nickel loading mole fraction (xNi). Upon activation with methylaluminoxane (MAO), this binary catalytic system showed activities varying from 12.3 to 309.1 kg of PE · (mol[M] · atm · h)−1. The properties of the polymeric materials are influenced by xNi as well as by the temperature of polymerization, affording the copolymers with a melting point (Tm) between 118 and 135 °C. The GPC results show that the molecular weight ($\overline M _{\rm w}$) of the polymers is sensitive to the xNi. In all of the cases studied, the GPC curves displayed monomodal molecular weight distributions (MWDs) with the average molecular weight varying from 30 000 to 507 000 g · mol−1. Studies using dynamic mechanical thermal analysis (DMTA) show that the formation of different polymeric materials is associated with the branching content, with the stiffness varying according to the xNi and the temperature used in the polymerization reaction.Overview of the copolymerization process, from ethylene in the presence of MAO, mediated by catalysts 1 and 2/SMAO.imageOverview of the copolymerization process, from ethylene in the presence of MAO, mediated by catalysts 1 and 2/SMAO.

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“…Preparation of SiO 2 /MAO (4.0 wt.-% Al/SiO 2 ) [16] MAO-modified silica was prepared by impregnating 1.0 g of thermally treated silica with the MAO-toluene solution at room temperature for 3 h under stirring. The solvent was removed under vacuum and the remaining solid was dried.…”

Section: General Proceduresmentioning

confidence: 99%

Ethylene Polymerization using Combined Ni and Ti Catalysts Supported in situ on MAO‐Modified Silica

Junges

Souza

Santos

et al. 2005

Macro Materials & Eng

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Summary: Branched polyethylene/linear polyethylene blends (BPE/LPE) were prepared using the combined Ni(α‐diimine)Cl2 (1) (α‐diimine = 1,4‐bis(2,6‐diisopropylphenyl)acenaphthenediimine) and {TpMs*}TiCl3 (2) (TpMs* = hydridobis(3‐mesitylpyrazol‐1‐yl)(5‐mesitylpyrazol‐1‐yl)) catalysts supported in situ on methylaluminoxane (MAO)‐modified silica (4.0 wt.‐% Al/SiO2). The polymerization reactions were performed in toluene at two different polymerization temperatures (0 and 30 °C) and several nickel molar fractions (xNi), using MAO as external cocatalyst. At all temperatures, the activities show an approximate linear correlation with xNi, indicating a non‐synergistic effect between the nickel and the titanium species. Higher activities were found at 0 °C. The melting temperatures for the polyethylene blends produced at 0 °C decrease as xNi increases in the medium, indicating good compatibility between the polyethylene phases made by both catalysts. The melting temperature (Tm) of the polyethylene blends was shown to depend on the order in which the catalysts were immobilized on the MAO‐modified silica support. The initial immobilization of 1 on the support (2/1/SMAO‐4) affords polymers with a lower Tm than those produced with 1/2/SMAO‐4. In addition, scanning electron microscopy (SEM) studies revealed that the spherical morphology of the supported catalyst is replicated in the polyethylene particles.Influence of polymerization temperature on the activity of 1/2/SMAO‐4 with varying xNi.magnified imageInfluence of polymerization temperature on the activity of 1/2/SMAO‐4 with varying xNi.

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Characterization of MAO-modified silicas

Cited by 32 publications

References 28 publications

Effect of MAO silica surface loading on (nBuCp)2ZrCl2 anchoring, on catalyst activity and on polymer properties

Effect of MAO silica surface loading on (nBuCp)2ZrCl2 anchoring, on catalyst activity and on polymer properties

Tandem Action of Tp^MsNiCl and Supported Cp₂ZrCl₂ Catalysts for the Production of Linear Low‐Density Polyethylene

Ethylene Polymerization using Combined Ni and Ti Catalysts Supported in situ on MAO‐Modified Silica

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Characterization of MAO-modified silicas

Cited by 32 publications

References 28 publications

Effect of MAO silica surface loading on (nBuCp)2ZrCl2 anchoring, on catalyst activity and on polymer properties

Effect of MAO silica surface loading on (nBuCp)2ZrCl2 anchoring, on catalyst activity and on polymer properties

Tandem Action of TpMsNiCl and Supported Cp2ZrCl2 Catalysts for the Production of Linear Low‐Density Polyethylene

Ethylene Polymerization using Combined Ni and Ti Catalysts Supported in situ on MAO‐Modified Silica

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Tandem Action of Tp^MsNiCl and Supported Cp₂ZrCl₂ Catalysts for the Production of Linear Low‐Density Polyethylene