chain growth product forming an ethylene depleted first chain growth product c distilling said ethylene depleted first chain growth product whereby c 4 14 u03b1 olefins are distilled from said ethylene depleted first chain growth product leaving a bottoms stream comprising mainly poisson distributed tri c 2 20 alkyl aluminum and c 14 u03b1 olefins d conveying at least part of said bottoms stream to a c 4 8 olefin displacement zone maintained under displacement conditions and feeding c 4 8 olefin to said displacement zone thereby forming a c 4 8 olefin displaced product comprising mainly tri c 4 8 alkyl aluminum ethylene and c 4 20 u03b1 olefins e conveying said c 4 8 olefin displaced product to a second ethylene chain growth reaction zone maintained under chain growth conditions and feeding ethylene to said second ethylene chain growth zone thereby forming a second chain growth product comprising mainly ethylene c 4 20 u03b1 olefins and poisson distributed tri c 4 20 alkyl aluminums f vaporizing ethylene from said second chain growth product forming an ethylene depleted second chain growth product g distilling said ethylene depleted second chain growth product whereby c 4 14 u03b1 olefins are distilled from said ethylene depleted second chain growth product leaving a bottoms stream as defined in step.