Supported ((BuCP)-Bu-n)(2)ZrCl(2)Catalysts: Effects of selected Lewis acid organotin silica surface modifiers on ethylene polymerization

This study investigated the effects of several organotin silica surface modifiers on the ethylene polymerization performance of ((BUCP)-B-n)(2)ZrCl2-based supported catalysts in which MAO and metallocene were sequentially loaded. Each organotin compound acted as a spacer, increasing the catalyst activity. However, the catalyst activity and (M) over bar of the resulting polyethylenes varied as follows: Activity and fractional Sn+ charge: (BuSn)-Bu-n(OH)(2)Cl > MeSnCl3 > (BuSnCl3)-Bu-n > Reference catalyst; and, (M) over bar (w) : Reference catalyst > (BuSnCl3)-Bu-n > MeSnCl3 > (BuSn)-Bu-n(OH)(2)Cl. The above catalyst activity rating was explained considering the influence of the Lewis acidity, that is, the fractional Sn+ charge of the organotin modifiers on the generation, concentration, and electron density at the active [((BUCP)-B-n)(2)ZrMe](+) cation. All the catalysts showed fairly stable kinetic profiles and produced narrow molecular weight distribution resins; 2.8 <= PDI <= 3.