for example trimethylaluminum and tri isobutyl aluminum with water yields so called modified or mixed alumoxanes preferred alumoxanes are methylalumoxane and methylalumoxane modified with minor amounts of other higher alkyl groups such as isobutyl alumoxanes generally contain minor to substantial amounts of starting aluminum alkyl compounds the preferred co catalyst prepared either from trimethylaluminum or triethylaluminum is sometimes referred to as poly methyl aluminum oxide and poly ethyl aluminum oxide respectively the alumoxane co catalyst is a predominately located on the surface of the polyamide support particles the orientation of the alumoxane on the surface of the support particles functions to activate the subsequently added metallocene in carrying out the polymerization reaction the normal practice is to employ a scavenging agent or polymerization co catalyst which is added to the polymerization reactor along with the supported metallocene these scavengers can be generally characterized as organo metallic compounds of metals of groups ia iia and iiib of the periodic table of elements as a practical matter organo aluminum compounds are normally used as co catalysts in polymerization reactions specific examples include triethyl aluminum tri isobutyl aluminum diethyl aluminum chloride diethyl aluminum hydride and the like scavenging co catalysts normally employed in the invention include triethyl aluminum teal and tri isobutyl aluminum tibal tri isobutyl aluminum can also be employed as a dispersant in which the supported catalyst is aged for a suitable period of time of.