Ethylene polymerization with phillips catalyst Co-catalyzed with Al(i-Bu)3

Abstract

The kinetics of ethylene polymerization with CrO 3/SiO 2/Al(i-Bu) 3 has been investigated in the range of temperatures between 323 and 353 K and in the range of pressures between 116.7 and 268.7 psia. The effects of aluminum alkyl on the formation and the deactivation of active sites are discussed. The rate of polymerization is considered to occur between adsorbed monomer and an active center, and the change in the polymerization rate at the initial period is described by formation of active sites from the interaction of adsorbed aluminum alkyl with preactive sites. Decay of the polymerization rate, which was independent of the monomer concentration, is ascribed to the excess aluminum alkyl that could poison the active sites by the Langmuir-Hinshelwood mechanism. Activation energy obtained from the maximum polymerization rates between 323–353 K was 8.8 kcal/mol. An apparent negative activation energy was obtained above 343 K and is ascribed to the destruction of active sites.Oa 1990 Academic Press, Inc.