EFFECTS OF EXTERNAL DONOR ON ACTIVE CENTER DISTRIBUTION OF SUPPORTED ZIEGLER-NATTA CATALYST
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EFFECTS OF EXTERNAL DONOR ON ACTIVE CENTER DISTRIBUTION OF SUPPORTED ZIEGLER-NATTA CATALYST
Vol. 15, Issue 3, Pages: 217-225(1997)
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Published:20 September 1997
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FAN Zhiqiang, M.CarmelaSacchi, PaoloLocatelli. EFFECTS OF EXTERNAL DONOR ON ACTIVE CENTER DISTRIBUTION OF SUPPORTED ZIEGLER-NATTA CATALYST[J]. 1997, 15(3): 217-225.
DOI:
FAN Zhiqiang, M.CarmelaSacchi, PaoloLocatelli. EFFECTS OF EXTERNAL DONOR ON ACTIVE CENTER DISTRIBUTION OF SUPPORTED ZIEGLER-NATTA CATALYST[J]. 1997, 15(3): 217-225.DOI:
EFFECTS OF EXTERNAL DONOR ON ACTIVE CENTER DISTRIBUTION OF SUPPORTED ZIEGLER-NATTA CATALYST
The composition distribution (CD) and microisotacticity distribution (ID) of propene/1-hexene copolymer synthesized by MgCl2/DIBP/TiCl4 (DIBP: diisobutyl phthalate) weredetermined by fractionating the copolymers according to crystallinity and characterizingthe fractions by 13CNMR. The effects of two alkoxysilane donors
triethoxyphenylsilane(PTES) and dimethoxydi-tert-butylsilane (TBMS)
on CD and ID of the copolymrs werecompared. Three main parts in the CD diagram of each copolymer were distinguished
which were correlated to active center distribution (ACD) based on three groups of different active centers.By studying the changes in 1-hexene content
microisotacticity and reactivity ratio product of three typical fractions
the effects of external donor on ACD were better elucidated.It was found that TBMS shows much stronger effects on ACD than PTES.In the former system
most fractions were produced on active centers with relatively lower r1 r2
higher reactivity to 1-hexene
and higher stereospecificity as compared to the system without external donor.It is concluded that the observed very extensive changes in ACD are mainly resulted by the formation of new types of active centers
possibly by coordination of external donor to certain positions on the catalyst.
Abstract
The composition distribution (CD) and microisotacticity distribution (ID) of propene/1-hexene copolymer synthesized by MgCl2/DIBP/TiCl4 (DIBP: diisobutyl phthalate) weredetermined by fractionating the copolymers according to crystallinity and characterizingthe fractions by 13CNMR. The effects of two alkoxysilane donors
triethoxyphenylsilane(PTES) and dimethoxydi-tert-butylsilane (TBMS)
on CD and ID of the copolymrs werecompared. Three main parts in the CD diagram of each copolymer were distinguished
which were correlated to active center distribution (ACD) based on three groups of different active centers.By studying the changes in 1-hexene content
microisotacticity and reactivity ratio product of three typical fractions
the effects of external donor on ACD were better elucidated.It was found that TBMS shows much stronger effects on ACD than PTES.In the former system
most fractions were produced on active centers with relatively lower r1 r2
higher reactivity to 1-hexene
and higher stereospecificity as compared to the system without external donor.It is concluded that the observed very extensive changes in ACD are mainly resulted by the formation of new types of active centers
possibly by coordination of external donor to certain positions on the catalyst.
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