Olefin polymerization using supported metallocene catalysts: development of high activity catalysts for use in slurry and gas phase ethylene polymerizations

Harrison, Daryll G.; Coulter, Ian M; Wang, Shaotian; Nistala, Satayrayana; Kuntz, Bradley A.; Pigeon, Michael; Tian, Jinfeng; Collins, Scott

doi:10.1016/s1381-1169(97)00163-5

Cited by 81 publications

(46 citation statements)

References 22 publications

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“…The activity drop has been attributed to (1) geometric restrictions of monomer access to the active sites 1,2 or the limitation of metallocene-MAO interaction due to isolated confinement; 3 (2) the deactivation of metal centers during the immobilization, which results in low ratios of activeto-total transition metal centers; 4,5 and (3) a decrease in the propagation rate. 6 Occasionally, supported metallocene/MAO catalysts exhibit higher average activities than homogeneous ones due to more stable kinetic profiles. 4 It has long been known that catalyst morphology has a strong influence on the initial fragmentation and, hence, polymerization behavior of supported catalysts.…”

Section: Introductionmentioning

confidence: 99%

Influence of support friability and concentration of α‐olefins on gas‐phase ethylene polymerization over polymer‐supported metallocene/methylaluminoxane catalysts

Hammawa

Wanke

2007

J of Applied Polymer Sci

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The effects of support friability (F) and ethylene/comonomer ratios were investigated over supported metallocene/methylaluminoxane catalysts prepared with nine different porous polymeric supports and various comonomer concentrations with a 2-L reactor operated in the semibatch gas-phase mode at 808C and 1.4 MPa. F of the supports was measured with a newly devised method. The performance of the supported catalysts depended on support F as follows. The average homopolymerization activities varied from less than 6 t of polyethylene (PE) (mol of Zr)À1 h À1 for low-F catalysts to 10-20 t of PE (mol of Zr)À1 h À1 for moderate-F catalysts and up to 100 t of PE (mol of Zr) À1 h À1 for the high-F catalysts. The presence of 1-hexene and propylene comonomers increased the activity of the low-F catalysts by up to 20-fold and 50-fold, respectively; that is, there were very marked comonomer effects. Activity enhancement by 1-hexene was less than 3-fold for the moderate-F catalysts, whereas the high-F catalysts showed little activity enhancement. Sometimes, 1-hexene even resulted in activity reductions. Very different particle morphologies were obtained with the catalysts of different F's.

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Section: Introductionmentioning

confidence: 99%

Influence of support friability and concentration of α‐olefins on gas‐phase ethylene polymerization over polymer‐supported metallocene/methylaluminoxane catalysts

Hammawa

Wanke

2007

J of Applied Polymer Sci

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“…As an example, random branching is caused by chaintransfer in the radical polymerization of low-density polyethylene (LDPE) as mentioned by Odian (1991), incorporation of vinyl-terminated chains in metallocenecatalyzed polyethylene (Harrison et al 1998;Tobita 1999;Beigzadeh et al 1999) or by crosslinking reactions with multifunctional monomers (Ferri and Lomellini 1999). For these randomly branched polymers, the molecular topology is not known in detail.…”

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confidence: 99%

Rheological properties of branched polystyrenes: linear viscoelastic behavior

et al. 2005

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“…41 In addition, simple metallocenes have been reported to produce LCB from slurry and gas-phase polymerizations. 42 We are not yet able to determine if COH bond activation plays a role in LCB formation from (CH 3 ) 2 Si(indenyl) 2 ZrCl 2 , but it does seem to be a possibility.…”

Section: Implications Of Mechanism On Other Catalyst Systemsmentioning

confidence: 96%