Alkanes from vanadium-based ethylene polymerizations were found to originate from ethylene insertion into the AI-R bond in the cocatalyst and from the polymerization catalyst. The alkanes from the catalyst mostly came from vanadium sites that are related to the silica support and the quantity of alkanes can be reduced by chemical treatment of the silica. The polymerization conditions also affected the quantity of alkanes with low hydrogen concentration, addition of comonomer, and the use of TMA (trimethylaluminum) as a cocatalyst reducing the concentration of alkanes in the polymer.