Supported ((BuCP)-Bu-N)(2)ZrCl(2)Catalysts: Effects Of Selected Lewis Acid Organotin Silica Surface Modifiers On Ethylene Polymerization

Abstract

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.