Mesoporous MCM-41(or AlMCM-41) molecular sieves were used as supports for preparing some supported metallocene catalysts, which should be pursued for the slurry or gas phase polymerization of ethylene.
Mesoporous molecular sieve AlMCM-41s were obtained by hydrothermal synthesis with Si/Al=60, 30 and 15,respectively. The TEM images and X-ray diffraction showed that AlMCM-41 had a uniform hexagonal array of linear channels constructed with a silica matrix like a honeycomb and about 40Å d-spacing.
The activities of ethylene polymerization over the metallocene catalyst directly supported on AlMCM-41(Metallocene/AlMCM -41) were higher than those over the metallocene catalyst supported on MAO pretreated AlMCM-41(Metallocene/MAO/ AlMCM-41). All the metallocene catalysts supported on AlMCM-41 with lower Si/Al ratio showed higher catalytic activity, and this is due to larger number of Lewis acid sites.
The sizes of all the polymer particles were rather uniform. However, the polymer morphologies from $Cp_2ZrCl_2$/MAO/AlMCM-41 are spherical, which those from $Cp_2ZrCl_2$/AlMCM-41 are sponge-like.
