Effects of aluminoxane cocatalysts on bis(imino)pyridine iron-catalyzed ethylene oligomerization

Ethylene oligomerization facilitated with a bis(imino)pyridine iron catalyst in the presence of various aluminoxane cocatalysts is investigated in this work. The effects of different trialkylaluminiums and [H2O]/[Al] molar ratios employed in the synthesis of aluminoxanes on the catalytic activity, selectivity to linear alpha-olefins, and polymer share have been discussed. The results show that MAO-S (methylaluminoxane synthesized herein) renders the highest catalytic activity but with a rather high undesired polymer share, and i-BAO (iso-butylaluminoxane) is the most optimum cocatalyst, rendering the predominant production of alpha-olefins at high activity with significantly reduced polymer share. On the contrary, EAO (ethylaluminoxane) shows quite poor catalytic activity. The use of mixed aluminoxanes, MBAO (mixed aluminoxanes synthesized from trimethylaluminium and triisobutylaluminium mixtures), and EBAO (mixed aluminoxanes synthesized from triethylaluminium and triisobutylaluminium mixtures) as cocatalysts also renders different catalytic performance, indicating that the composition/structure of mixed aluminoxanes has pronounced effects on the catalytic activity and selectivity to linear alpha-olefins.