surface. However, a careful analysis of many images of the polymer
suggests a relatively low polydispersity of polyethylene. Indeed
this is in agreement with the low MWD values obtained for the
polyethylene produced using the MBA-Ti catalyst (Table 1).
support and Ti, which reduces the specific activity of Ti towards
polymerization.
Acknowledgements
4. Origin of activity
SEG and KST thank CSIR, New Delhi for Senior Research
Fellowship. We thank Reliance Industries Limited, Mumbai, India
for financial support.
The detailed preparation, characterization by structural, spectro-
scopic and microscopic analytical methods and the evaluation
of the titanated adducts for ethylene polymerization presented
here provide some new information, especially on the molecular
level properties and electronic structure of the molecular adducts
and corresponding Ziegler catalysts. Although there is already
some similar information available in the literature,17–19,37 it is
derived from the analysis of polymer products and hence in an
indirect manner. A few points are worth highlighting regarding
the influence on catalytic activity. (a) The structure and spectral
properties of the MBA adduct and MBA-Ti catalyst have been suf-
ficiently demonstrated by XRD, NMR, and Raman spectroscopy.
(b) Significant changes in the Raman spectra of MBA and MEA
have been observed, indicating a stronger interaction between Mg
and O in MBA than MEA. (c) A marginally lower polymerization
activity is observed with MBA-Ti compared to MEA-Ti in spite
of a higher surface area. MBA-Ti in spite of its high titanium
content shows a lower specific activity towards polymerization. In
Ziegler catalysts, partial reduction of the catalytically active Ti4+/3+
to Ti2+ in a side reaction with TEAL is known to be one of the
main catalyst deactivation pathways. In our earlier publication we
presented evidence indicating that PhCO2Et, a so called internal
electron donor, makes the catalyst more resistant towards quick
deactivation by co-ordination to the Ti4+ center. In the present
case the larger pores probably make the catalytically active Ti4+/3+
sites more accessible to TEAL resulting in over-reduction and
deactivation. Further benzyl chloride trapped in the pores might
also be blocking some of the active sites.
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5. Conclusion
A new single phase supporting material for Ziegler–Natta catalysts
with an aromatic alcohol (benzyl alcohol) adduct of MgCl2 has
been successfully synthesized and characterized by variety of
analytical and spectroscopic characterization methods. Notably
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spectra. The titanated MBA catalyst has been characterized by
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