Polymerization mechanism for in situ supported metallocene catalysts

The polymerization of ethylene was carried out with a novel in situ support ed metallocene catalyst that eliminated the need for a supporting step befo re polymerization. In the absence of trimethyl aluminum (TMA), in situ supp orted Et[Ind](2)ZrCl2 was not active, but the addition of TMA during polyme rization activated the catalyst. Et[Ind](2)Zr(CH3)(2) was active even in th e absence of TMA, whereas the addition of TMA during polymerization enhance d the catalytic activity. The polymerization-rate profiles of the in situ s upported metallocene catalysts did not show rate decay as a function of tim e. A polymerization mechanism for the in situ supported metallocene catalys ts is proposed for this behavior. During polymerization, the in situ suppor ted metallocene catalysts may deactivate, but homogeneous metallocene speci es present in the reactor may form new active sites and compensate for deac tivated sites, (C) 2000 John Wiley & Sons, Inc.