(608b) Silica Tethered Sulfonic Acids for Activation of Olefin Polymerization Catalysts

A variety of co-catalysts have been developed to activate metallocenes for the polymerization of olefins including methylaluminoxane (MAO), boranes, borates and sulfated metal oxides. MAO or borane based co-catalysts are most commonly used as activators for polymerization of olefins. However, these technologies represent relatively expensive co-catalysts. Basic raw material cost calculations show that co-catalysts such as MAO can represent over 60% of the cost of typical polymerization recipes. Thus, alternative, low cost replacements for these co-catalysts are continuously being sought. For the first time, the utilization of an organic/inorganic hybrid material is reported as a co-catalyst for borane and MAO-free metallocene activation for olefin polymerizations. Silica tethered sulfonic acids combined with small amounts of trimethylaluminum (TMA) or triisobutylaluminum (TIBA) act as activators for either Cp*₂ZrCl₂ or Cp*₂ZrMe₂ in the polymerization of ethylene. Various control experiments indicate that the in-situ formation of the known co-catalyst MAO is not likely the mechanism of activation. Similar to sulfated metal oxides (SMOs), the catalytic activation step most likely occurs via metal-carbon protonolysis. This is a new, potentially low cost activator/support for single-site olefin polymerization.