Preparation of polymerization catalyst activators utilizing indole-modified silica supports

A process for polymerizing propylene comprising:

• contacting propylene and optionally one or more monomers with a catalyst system comprising a bis-indenyl Group 4 metallocene compound supported on silica, said (silica having been treated with one or more organoaluminum compounds and one or more heterocyclic compounds, under slurry conditions in the presence of hydrogen at a temperature of about 50° C. to about 160° C. and a pressure of from about 3 MPa to about 20 MPa to provide a catalyst activity of greater than 30,000 pounds of product per pound of catalyst;
• and then
• recovering isotactic polypropylene having a melt flow rate of 20 dg/min or less, wherein the one or more heterocyclic compounds are represented by formula (I):
• where each of X2 to X7 is independently hydrogen, halogen, an alkyl group, a halogenated or partially halogenated alkyl group, an aryl group, an alkoxide group, a halogenated or partially halogenated alkoxide group, an aryloxide group, a halogenated or partially halogenated aryloxide group, an aryl substituted alkyl group, or a halogenated or partially halogenated aryl substituted alkyl group.