Preparation of Aryloxy-aluminoxanes and Their Use as Activators in the Bis(imino)pyridyl Iron-catalyzed Oligomerization of Ethylene

In this study, a series of aryloxy-aluminoxanes originated directly from the hydrolysis of reaction products of AlMe 3 and phenols were synthesized, which could serve as effective polymer-retarding activators for the iron-catalyzed ethylene oligomerization. The molar ratios of [PhOH]/[AlMe 3 ] and [H 2 O]/[Al] during the preparation were explored and their impacts on the oligomerization activity and product distribution were discussed. To obtain the effective activators with good polymer-retarding effect and relatively high activity, the optimized conditions were proposed to be [PhOH]/[AlMe 3 ] = 0.5 and [H 2 O]/[Al] = 0.7. Various aluminoxanes with different [―OH] sources confirmed the importance of using phenols in preparing the effective polymer-retarding activators. By utilizing these aryloxy-aluminoxanes, the mass fraction of polymers in the total products could be reduced to lower than 1.0 wt%, which is much lower than that of the MAO-activated systems (> 30 wt%). This is a potential benefit for the industrial application of the iron-catalyzed oligomerization process.