a method for removing catalyst from an olefinic oligomerization product includes the steps of oligomerizing one or more olefins in the presence of a bf 3 cocatalyst complex , and distilling the oligomerization product while separating vaporized bf 3 cocatalyst complex , the distillation step including , simultaneously to the separation of bf 3 cocatalyst complex , a separation of vaporized unreacted monomer from a bottom product which becomes substantially free from bf 3 cocatalyst complex .