Cr(III)-based catalyst system for oligomerization of ethylene to 1-octene with high selectivity

A four-membered catalyst system (chromium acetyl acetonate (Cr(acac)(3))-diphosphinoamine-methylaluminoxane-hexachloroethane) was used in ethylene oligomerization. The effects of promoters, cocatalysts, and reaction conditions such as Al/Cr molar ratio, reaction temperature, and reaction pressure on its catalytic activity and selectivity for 1-octene were studied. The results showed that the four-membered catalyst system for ethylene oligomerization improved the selectivity for 1-octene evidently. Besides the target product 1-octene, main side-products such as 1-hexene, methylcyclopentane, and methylenecyclopentane were also valuable. Methylaluminoxane was an indispensable cocatalyst for producing 1-octene with high selectivity. Hexachloroethane showed a significant promotion effect on improving selectivity towards 1-octene over chromium centers.