A KINETIC-STUDY ON ETHYLENE POLYMERIZATION BY CP2ZRCL2 ISO-BUTYLALUMOXANE/

iso-Butylalumoxane (BAO) has been synthesized and characterized, and e thylene polymerization catalyzed by Cp2ZrCl2/BAO has been investigated . The polymerization rate curves at different catalyst concentrations, Al/Zr molar ratio and polymerization temperature are determined and c ompared to the kinetic behavior of ethylene polymerization catalyzed b y Cp2ZrCl2/methylalumoxane (MAO) reported in literature. On the basis a tentative model for the cocatalytic action of BAO has been proposed: only a kind of multi-molecular aggregates of BAO can act as cocatalys t of metallocenes. Because of the low stability of the BAO aggregates, Cp2ZrCl2/BAO system shows a moderate catalytic activity only at relat ively high BAO concentration and medium temperature. The main reason f or the lower activity of BAQ than MAO is the absence of highly active species which is stable at low concentration and high temperature.