Ethylene homo- and copolymerization using (nBuCp)2ZrCl2 grafted on silica modified with different spacers

Galland, Griselda B.; Santos, João Henrique Zimnoch dos; Stedile, Fernanda Chiarello; Greco, Paula Palmeira; Campani, Adriano D

doi:10.1016/j.molcata.2003.09.007

Cited by 12 publications

(12 citation statements)

References 20 publications

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“…This represents a great success in the metallocene heterogeneous catalyst for ethylene polymerization. Activities reported in the polymerization of ethylene are in the order of half the value obtained for the homogeneous system when using silica modified with different spacers 4, 36…”

Section: Resultsmentioning

confidence: 91%

“…A small band at 3745 cm −1 , assigned to isolated silanol groups (SiOH i ),21 was superimposed to the broad band centered at 3400 cm −1 . The amount and accessibility of silanol groups of silica depends on previous thermal treatments 4–6, 22, 23. Silica samples were heated from 25 to 140 °C in the DRIFT cell under a constant helium flow.…”

Section: Resultsmentioning

confidence: 99%

“…A strategy to overcome these problems has been the use of different molecules as vertical spacers between catalyst and support. This leads to better polymer properties and catalyst activities than those obtained when the metallocene is directly supported over silica 4–6. Polyhedral oligomeric silsesquioxanes (POSSs) have been proposed as silica modifiers.…”

Section: Introductionmentioning

confidence: 99%

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Metallocene supported on a polyhedral oligomeric silsesquioxane‐modified silica: Structural characterization and catalytic activity for ethylene polymerization

García-Orozco

Velilla

Galland

et al. 2010

J. Polym. Sci. A Polym. Chem.

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Preliminary results on the activity of metallocene supported over a polyhedral oligomeric silsesquioxane (POSS)modified silica for ethylene polymerization (Bianchini et al., J Polym Sci Part A: Polym Chem 2005, 43, 5465-5476) were extended showing the effect of large variations of the amount of both POSS and metallocene on the catalyst activity. Diffuse reflectance infrared spectroscopy results showed that at low concentrations (<1 wt %), POSS was physically adsorbed on SiOH groups present in the silica surface through H-bonds. At larger concentrations, POSS was adsorbed by covalent bonds with the silica surface. The metallocene catalyst was adsorbed either on the silica surface by interactions with residual SiOH groups or in the organic branches of the POSS. It was found that the highest contribution to the catalyst activity arose from the metallocene directly adsorbed on the silica support. The effect of POSS to increase the catalyst activity was mainly due to its effect as a horizontal spacer of metallocene molecules adsorbed on the silica surface. An optimum range of POSS and metallocene adsorbed on the silica support was found that gave catalyst activities close to the one of the homogeneous system while doubling the molar mass of the polyethylene produced. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 5938-5944, 2010

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Section: Resultsmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Metallocene supported on a polyhedral oligomeric silsesquioxane‐modified silica: Structural characterization and catalytic activity for ethylene polymerization

García-Orozco

Velilla

Galland

et al. 2010

J. Polym. Sci. A Polym. Chem.

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“…[14] Many studies concerning the effect of metallocene structure, comonomer type and concentration on catalyst copolymerisation reactivity and copolymer properties have been carried out. [2,3,9,11,13,[15][16][17][18][19][20][21][22][23][24][25][26][27] It was found that the homogeneous zirconocene dichloride or dialkyl complexes containing Cp ligands were more active in the copolymerisation of ethylene with 1-hexene than catalysts with Ind ones. Both catalytic systems, however, showed a very similar ability to incorporate comonomers into polyethylene chains.…”

Section: Introductionmentioning

confidence: 99%

(Co)polymerisation Behaviour of Supported Metallocene Catalysts: Carrier Effect

Białek

Czaja

2006

Macro Chemistry & Physics

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The polymerisation and copolymerisation of ethylene with 1-hexene over metallocene catalysts L 2 ZrCl 2 / MAO (L ¼ Cp, n-BuCp, t-BuCp, i-PrCp, Me 5 Cp) supported on different types of carriers (MgCl 2 (MeOH) 6 or silica with CH 3 surface groups obtained in the sol-gel process) were studied. It was demonstrated that both the metallocene structure and the type of inorganic support affected catalyst activity and polymer properties such as melting point, molecular weight and molecular weight distribution. The metallocene structure also determined comonomer incorporation, both for homogeneous and supported catalytic systems. When a catalyst is anchored on a support, it becomes less effective at incorporating a comonomer into the polyethylene chain, and the type of the support material has no influence on that process. The type of carrier used does, however, have an influence on the molecular weight and molecular weight distribution of the product obtained. Most polymers and copolymers obtained with catalysts supported on an oxide carrier have higher molecular weights and broader molecular weight distributions than those produced by catalysts anchored on a magnesium compound.Melting curves (obtained using the SSA method) of ethylene/1-hexene copolymers synthesised with Cp 2 ZrCl 2 /MAO (A) and with the same catalyst supported on various carriers (B,C,D).

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“…Therefore, bimolecular deactivation reactions between two neighboring zirconocene sites were hindered. The substituents present in the silane can also play a role on the reaction mechanism 3…”

Section: Introductionmentioning

confidence: 99%

Metallocene supported on a polyhedral oligomeric silsesquioxane‐modified silica with high catalytic activity for ethylene polymerization

Bianchini

Galland

Santos

et al. 2005

J. Polym. Sci. A Polym. Chem.

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A polyhedral oligomeric silsesquioxane (POSS) consisting of a mixture of perfect and imperfect polyhedra with 8-10 Si atoms bonded to bulky and branched organic groups functionalized with (b-hydroxy)-tertiary amines, was adsorbed on an activated silica from a toluene solution. POSS fixation was confirmed by measuring its concentration in the solutions resulting from filtering and repeatedly washing with toluene. Diffuse reflectance infrared Fourier-transformed (DRIFTS) spectra of the modified silica showed a decrease in the absorption of isolated SiOH groups. A POSS previously marked by reaction with an isocyanate was also used, and the presence of the carbonyl in the urethane group was recorded in the DRIFTS spectra of the modified silica, confirming the presence of adsorbed POSS. X-ray photoelectron spectroscopy (XPS) was used to measure the amount of Si (2p) of POSS adsorbed on the SiO 2 surface as a function of the POSS concentration in the toluene solution. A linear increase of adsorbed POSS as a function of its concentration in toluene was found, even after successive washings with toluene. A metallocene, (nBuCp) 2 ZrCl 2 , was then adsorbed on the POSS-modified silica from a toluene solution, and the fixed Zr amount was measured by Rutherford backscattering spectrometry (RBS). The activity of the resulting catalyst for ethylene polymerization in toluene, using methylaluminoxane (MAO) as a cocatalyst, was determined in two different devices operating in the range of 1.6-7.0 bar. Under every experimental condition, POSS-modification of the silica support led to an increase of about 50% in the activity of the resulting catalyst when compared to the use of the unmodified support. Reasons for the observed increase in activity are discussed. The molar mass distribution and crystallinity of the resulting polyethylenes was not affected by the POSS modification of the silica support.

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Ethylene homo- and copolymerization using (nBuCp)2ZrCl2 grafted on silica modified with different spacers

Cited by 12 publications

References 20 publications

Metallocene supported on a polyhedral oligomeric silsesquioxane‐modified silica: Structural characterization and catalytic activity for ethylene polymerization

Metallocene supported on a polyhedral oligomeric silsesquioxane‐modified silica: Structural characterization and catalytic activity for ethylene polymerization

(Co)polymerisation Behaviour of Supported Metallocene Catalysts: Carrier Effect

Metallocene supported on a polyhedral oligomeric silsesquioxane‐modified silica with high catalytic activity for ethylene polymerization

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