Supported ( n BuCp) 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 ( n BuCp) 2 ZrCl 2 ‐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 $\overline M _{\rm w}$ of the resulting polyethylenes varied as follows: Activity and fractional Sn + charge: n BuSn(OH) 2 Cl > MeSnCl 3  >  n BuSnCl 3  > Reference catalyst; and, $\overline M _{\rm w}$ : Reference catalyst >  n BuSnCl 3  > MeSnCl 3  >  n BuSn(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 [( n BuCp) 2 ZrMe] + cation. All the catalysts showed fairly stable kinetic profiles and produced narrow molecular weight distribution resins; 2.8 ≤ PDI ≤ 3.