Initial Rate and Aging Effect of Ethylene Polymerization with Ziegler-Natta Catalysts. III

The initial rate and the aging effect of ethylene polymerization with TiCl4- and TiCl3-AlEt3 catalyst were investigated. The initial rate, r, was expressed by the equation; r=k1PE+k2PE2, where pE is the ethylene partial pressure and where k1 and k2 are constants. The explanation of the equation is as follows:&(active site)+M\xrightarrowk_1(polymerization site), rate, k_1P_E&(polymerization site)+M^*\xrightarrowk_2(propagation), rate, k_2P_E^2M shows the ethylene monomer which is liberated by the catalyst formation or which is introduced into the system. M* is the monomer which is introduced into the system. The initial rate decreased in the TiCl4-AlEt3 system with the aging-time interval; on the other hand, in the TiCl3-AlEt3 system the rate showed its maximum at about half an hour’s aging. The optimum aging temperature was found to be 20°C. The decrease in the rates between the two systems may be ascribed to the reduction of the Ti atom in the initial valence state of the reaction to the lower valence.