The characteristics of metallocene/Ziegler-Natta hybrid catalysts supported on the recrystallized MgCl2 |
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Authors: | Young Gwan Ko Han Seock Cho Ki Ho Choi Wha Young Lee |
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Affiliation: | (1) Division of Chemical Engineering, College of Engineering, Seoul National University, Shillim-Dong, Kwanak-Ku, 151-742 Seoul, Korea |
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Abstract: | A metallocene catalyst or a metallocene/Ziegler-Natta hybrid catalyst supported on MgCl2 was studied for application to the commercial slurry phase process and to the control of MWD of the polymer produced. The
MgCl2 support was prepared by the recrystallization method with different solvents: alcohols and H2O. The recrystallized MgCl2 support was pretreated with triisobutylaluminum (TiBAL) or trimethylaluminum (TMA), methylaluminoxane (MAO), to give different
supporting environments. Metallocene/Ziegler-Natta hybrid catalysts on MgCl2 were prepared by first supporting the metallocene catalyst, followed by the Ziegler-Natta catalyst after pretreatment with
an alkylaluminum compound. The type of solvent plays a role in providing a suitable environment in the support for impregnating
catalysts. The hybrid catalyst, whose support was recrystallized in n-propanol (n-PrOH) and pretreated with TiBAL, showed
the highest molar ratio of Zr/Ti= 1/2.71. But the hybrid catalyst, whose support was recrystallized in H2O and pretreated with MAO, showed the best hybrid effect showing a variety of bimodal peaks in proportion to the ratio of
MAO/TEA in GPC analysis. This effect might be due to steric factor and polarity of solvent, as well as the pretreatment material.
It is concluded that the MWD of polyethylene produced by metallocene/Ziegler-Natta hybrid catalyst that is supported on MgCl2 can be controlled by regulating the amounts of MAO and TEA added as cocatalysts and by the use of different solvents and
pretreatment materials. |
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Keywords: | Recrystallized MgCl2 Solvent Pretreatment Material Metallocene/Ziegler-Natta Hybrid Catalyst Ethyl-ene Polymerization Hybrid Effect |
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