Influence of Cocatalysts on the Performance of Postphthalate Supported Ziegler–Natta Catalysts in Gas-Phase Propylene Polymerization

The performance of triethyl-, triisobutyl-, and trioctylaluminum (TEA, TiBA, and TOA, respectively) as cocatalysts was evaluated using a postphthalate Ziegler–Natta catalyst system for the gas-phase polymerization of propylene under various reaction conditions. The lowest catalyst activity was observed with TEA, which is due to its power of over-reduction for the active sites, while the highest catalyst activities were observed with TiBA. Moreover, the molecular weight of the final polymer with TiBA and TOA was much higher than with TEA overall, in addition to the overall mildly narrower distribution for TOA compared to TEA and TiBA. Moreover, this catalyst’s stereoregular response is not very dependent on the cocatalyst; however, the highest isotacticity was observed when TiBA was used. The effects on the powder morphology in terms of settled bulk density and fines content were not pronounced or related to most of the reaction conditions with the different cocatalysts except for the conditions of initiation, which was reflected in the overall lower bulk densities with TOA, for which the reaction initiation is much milder than for the other two cocatalysts.