The present study showed enhanced activities of ethylene/1-octene copolymerization via TiO 2 -SiO 2 mixed oxides-supported MAO with a zirconocene catalyst. It was proposed that titania was decorated on silica surface and acted as a spacer to anchor MAO to the silica support resulting in less steric hindrance and less interaction on the support surface.
Activities during ethylene/1-hexene copolymerization were found to increase using the mixed titania/silica-supported MAO with rac-Et[Ind]2ZrCl2 metallocene catalyst. Energy Dispersive X-ray spectorcopy (EDX) indicated that the titania was apparently located on the outer surface of silica and acted as a spacer to anchor MAO to the silica surface. IR spectra revealed the Si-O-Ti stretching at 980 cm-1 with low content of titania. The presence of anchored titania resulted in less steric hindrance and less interaction due to supporting effect.
The present study focused on the application of mixed TiO 2 -SiO 2 -supported methylaluminoxane (MAO) with a zirconocene catalyst on the linear low-density polyethylene (LLDPE) production. At low concentrations of TiO 2 present in the mixed supports, it revealed that TiO 2 was decorated on the SiO 2 surface and acted as a spacer to anchor MAO to the SiO 2 surface resulting in less steric hindrance and less interaction. As a result, catalytic activities via ethylene/1-olefin copolymerization apparently increased with the presence of TiO 2 . Besides increased activities, the presence of TiO 2 in the mixed supports can result in a slightly lower molecular weight (MW) of polymers, suggesting a higher chain transfer rate.
The bimodal polyethylene obtained from TiO 2 -supported zirconocene/MAO catalyst was observed during polymerization of ethylene and ethylene/1-hexene. By means of XPS, it revealed that TiO 2 consisted of Ti 3+ (BE = 462.6 eV) and Ti 4+ (BE = 464.9 eV). The dual catalytic sites were attributed to the presence of Ti 3+ and Ti 4+ in TiO 2 .
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