Ethylene polymerization was carried out by using the zirconocene catalysts
supported on MCM-41 (or Al-MCM-41), which had a uniform hexagonal array of
linear channels constructed with a honeycomb-like silica matrix, and about
40 Angstrom d-spacing. The zirconocene catalysts supported directly on sili
cious MCM-41 (Cp2ZrCl2/MCM-41) did not show any activity in ethylene polyme
rization. On the other hand, the activities of the zirconocene catalysts su
pported directly on Al-MCM-41 (Cp2ZrCl2/Al-MCM-41) were comparable to those
of homogeneous zirconocenes, and much higher than the activities of those
supported on Al-MCM-41 modified by methylaluminoxane (Cp2ZrC2,/MAO/Al-MCM-4
1). The Lewis acidity in Al-MCM-41 seemed to play an important role for anc
horing the zirconocenes, such that lower value of Si/Al ratio resulted in h
igher catalytic activity. Modification with MAO must have reduced the role
of acidity. The difference in the catalytic activity among the supported zi
rconocenes was discussed through the surface species models on the interact
ion between zirconocene and Lewis acids in Al-MCM-41. (C) 2000 Elsevier Sci
ence B.V. All rights reserved.