US Patent 10329212 Reduced polymer formation for selective ethylene oligomerizations

Disclosed are processes, systems, and reaction systems for the oligomerization of ethylene to form an ethylene oligomer product in a reaction zone using a catalyst system comprising (a) a chromium component comprising an N2-phosphinyl amidine chromium compound complex, an N2-phosphinyl formamidine chromium compound complex, an N2-phosphinyl guanidine chromium compound complex, or any combination thereof, and (b) an aluminoxane. A C3+ olefin can be present in the reaction zone for a period of time, where the C3+ olefin is not an ethylene oligomer formed in-situ within the reaction zone.