Effects of Internal and External Donors on the Regio- and Stereoselectivity of Active Species in MgCl2-Supported Catalysts for Propene Polymerization

Chadwick, John C.; Morini, Giampiero; Balbontin, Giulio; Camurati, Isabella; Heere, Johannes J. R.; Mingozzi, Ines; Testoni, Fabio

doi:10.1002/1521-3935(20010601)202:10<1995::aid-macp1995>3.0.co;2-l

Cited by 128 publications

(121 citation statements)

References 20 publications

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“…Thus, this caused the decrease in activity for both catalysts [25]. However, Zhang et al reported that alkoxysilane requires the bulky hydrocarbon groups to prevent the removal of silane from the surface of catalyst via the complexation with cocatalyst [2,12,15]. In this work, CHMDMS can reduce the catalytic activity more than DMDMS did.…”

Section: Catalytic Activitymentioning

confidence: 72%

“…As described previously, the various kinds of electron donors were used in olefin polymerization such as monoester, diester, alkoxysilane, diether and etc [11,14]. Recently, phthalate based type or diester and alkoxysilane are typically used as internal and external donor, respectively [15]. Among various R1R2Si(OMe)2 types of external donor, cyclohexylmethyldimethoxysilane (CHMDMS) is more frequently used due to its effective performance to enhance the isotacticity of polypropylene without sacrificing the catalyst activity [2].…”

Section: Introductionmentioning

confidence: 99%

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Investigation of Alkoxysilanes in the Presence of Hydrogen with Ziegler-Natta Catalysts in Ethylene Polymerization

Niyomthai¹,

Jongsomjit²,

Praserthdam³

2017

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Abstract. Effect of hydrogen and alkoxysilanes as external donor were investigated using two commercial Ziegler-Natta catalysts (TiCl4/MgCl2•nEtOH and TiCl4/phthalate type/MgCl2) in ethylene polymerization. These catalysts were analyzed by EDX, FTIR and XRD measurements. Furthermore, catalytic activity was tested. According to the results, when alkoxysilane was introduced into the system, catalytic activity reduced. Compared these two alkoxysilanes, cyclohexylmethyldimethoxysilane (CHMDMS) can decrease activity more than dimethoxydimethylsilane (DMDMS) did. This was because CHMDMS has more bulky hydrocarbon groups than DMDMS. This led to restrict the direction of monomer insertion to active sites. In addition, when hydrogen was added into the system, CHMDMS is more sensitive to hydrogen than DMDMS. However, CHMDMS showed lower hydrogen response than DMDMS with increased hydrogen concentration. This was owing to its hydrogen sensitivity. Among the two catalysts, catalyst having internal donor can decrease sensitivity of catalyst activity in the system with hydrogen. The obtained polymers were further characterized by DSC and GPC.

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Section: Catalytic Activitymentioning

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Investigation of Alkoxysilanes in the Presence of Hydrogen with Ziegler-Natta Catalysts in Ethylene Polymerization

Niyomthai¹,

Jongsomjit²,

Praserthdam³

2017

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“…This fact can be attributed to selective positions of EEDs, which suppress reactivity of the aspecific centers and may convert the aspecific centers into isospecific ones [25]. Moreover, with increasing hydrogen concentration, catalyst activities increased in all cases, as chain transfer with hydrogen leads to the regeneration of isospecific propagation [26][27][28]. From Table 1, we can find that the melt flow rates of the obtained iPPs catalyzed by catalysts with novel EED were much larger than expected.…”

Section: Resultsmentioning

confidence: 99%

Study on Hydrogen Sensitivity of Ziegler–Natta Catalysts with Novel Cycloalkoxy Silane Compounds as External Electron Donor

Wang

et al. 2016

Polymers

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Two novel cycloalkoxy silane compounds (ED1 and ED2) were synthesized and used as the external electron donors (EEDs) in Ziegler-Natta catalysts with diethyl 2,3-diisopropylsuccinate as internal electron donor. The results indicated that the Ziegler-Natta catalysts using ED1 and ED2 as EEDs had high catalytic activities and good stereoselectivities. The melt flow rate (MFR) and gel permeation chromatography (GPC) results revealed that the obtained polypropylene has higher MFR and lower average molecular weights than the commercial EED cyclohexyl methyl dimethoxysilane. The differential scanning calorimetry (DSC) results indicated that new isospecific active centers formed after the introduction of new external donors. The work implied that the novel EEDs could improve the hydrogen sensitivities of the catalyst system and obtain polymers with high melt flow rate.

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“…In the studies of external donor effects, information of the chain structure distribution is even more important than the isotacticity index. As reported by Chadwick J. C. et al [5,6], changing the external donor from cyclohexyl(methyl)-dimethoxysilane (CHMDMS) to dicyclopentyldimethoxysilane (DCPDMS) in propylene polymerization with a MgCl 2 /TiCl 4 /DIBP catalyst caused not only an increase in the polymer's isotacticity index, but also a remarkable shift of the TREF peak to the high temperature end. This means that raising PP isotacticity by using alkoxysilane external donor with bulky alkyl groups is usually accompanied by increase in the steroregularity of all the polymer chains.…”

Section: Introductionmentioning

confidence: 99%

Influences of silane/ether composite external donors on propylene polymerization with MgCl2-supported Ziegler-Natta catalyst in the presence of hydrogen

Lou

et al. 2011

E-Polymers

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Abstract:In this work, the effects of two silane type external donors, Ph 2 Si(OCH 3 ) 2 (DPDMS) and dicyclopentyldimethoxysilane (DCPDMS) on propylene slurry polymerization in the presence of hydrogen with a MgCl 2 /TiCl 4 /DIBP -Al(C 2 H 5 ) 3 catalyst system were investigated, and the tacticity distribution and molecular weight distribution (MWD) of polypropylene (PP) were further regulated by using silane/ether (ROCH 3 , R = n-Bu, i-C 8 H 17 ) composite external donors. The tacticity distribution of PP, as revealed by successive self-nucleation and annealing (SSA) thermo analysis of the polymer, is markedly changed by the external donors. DCPDMS shows much stronger effects than DPDMS. Addition of the ether as an auxiliary external donor in MgCl 2 /TiCl 4 /DIBP-TEA/silane (DPDMS or DCPDMS) lead to further increase in catalytic activity and isotacticity of PP, and changes in tacticity distribution. By using the composite external donors, PP with both higher isotacticity index, lower molecular weight or narrower molecular weight distribution was prepared at high activity. Effects of the external donors on the active center distribution were discussed based on the results of deconvoluting the MWD curve with multiple Flory "most-probable" distributions, and possible mechanism of the external donor effects was proposed.

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Effects of Internal and External Donors on the Regio- and Stereoselectivity of Active Species in MgCl2-Supported Catalysts for Propene Polymerization

Cited by 128 publications

References 20 publications

Investigation of Alkoxysilanes in the Presence of Hydrogen with Ziegler-Natta Catalysts in Ethylene Polymerization

Investigation of Alkoxysilanes in the Presence of Hydrogen with Ziegler-Natta Catalysts in Ethylene Polymerization

Study on Hydrogen Sensitivity of Ziegler–Natta Catalysts with Novel Cycloalkoxy Silane Compounds as External Electron Donor

Influences of silane/ether composite external donors on propylene polymerization with MgCl2-supported Ziegler-Natta catalyst in the presence of hydrogen

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