Highly Active FI Catalyst of Bis[N-(3,5-dicumylsalicylidene)cyclohexylaminato]-zirconium(IV) Dichloride for Polymerization of Ethylene

A highly active Zr-based FI catalyst of bis[N-(3,5-dicumylsalicylidene)cyclohexylaminato]zirconium(IV) dichloride was prepared and used for polymerization of ethylene. The catalyst displayed a very high activity of about 3.2x10(6) in ethylene polymerization at the monomer pressure of 3 bar using triisobutylaluminium (TIBA) and methylaluminoxane (MAO) as a scavenger and cocatalyst, respectively. The highest activity of the catalyst was obtained at about 35 degrees C. The polymerization activity was increased linearly with increased monomer pressure and [Al]:[Zr] ratio in the range studied. Introduction of bulky cumyl group on ortho position to the phenoxy oxygen prevents the catalyst from coordination to the cocatalyst following its easier coordination of ethylene to the active centres. The existence of bulky substitutions on the catalyst structure resulted in linear increase in its activity with increasing the MAO concentration through ion separation which facilitates the monomer insertion. However, fouling of the reactor was strongly increased with monomer pressure and the amount of MAO used. Ethylene polymerization was carried out using different amounts of hydrogen. The activity of the catalyst was slightly increased with addition of hydrogen; however, the viscosity average molecular weight ((M) over bar (v)) of the obtained polymer was not affected. In order to study the catalyst lifetime service, ethylene polymerization reactions were carried out at different reaction times while the temperature and [Al]/[Zr] molar ratio were kept constant. Despite the high activity, the catalyst showed a short lifetime. Crystallinity and melting point of the obtained polymer were between 55-65% and 125-130 degrees C, respectively. (M) over bar (v) Values of the obtained polymer were dropped as polymerization temperature increased, while higher pressure increased both the crystallinity and the (M) over barv values of the resulting polymer. Meanwhile some specifications of the obtained polymer were investigated.