Synthesis of alpha-olefin by oligomerization of ethylene (part 2) - Study of the mechanism of by-product formation

When alpha-olefin is synthesized by ethylene oligomerization, some by-produ cts are also formed at the same time. These by-products consist of branched -olefins, vinylidenes, internal olefins, and paraffins, and they an formed mainly when normal alpha-olefins are inserted into the metal-alkyl bond of the catalyst during oligomerization. In this study, Zr complex catalyst is used for oligomerization of ethylene, and the small amounts of by-products formed in normal alpha-olefin synthes is are analyzed, and also intermediate alpha-olefin insertion reaction is s tudied. As a result of the study, the mechanism of by-products formation ha s become clear. Branched-olefins and vinylidenes are formed by insertion of intermediate al pha-olefin into the growing chain of ethylene with Markovnikov addition. Th e reactivity of these normal alpha-olefins increased with decreasing carbon number. alpha-Olefin with N carbon number includes by-products, they are f ormed by insertion reaction of intermediate normal a-olefin with carbon num ber 4 to (N-2). Therefore, the by-products increase with increasing carbon number of normal alpha-olefins. All internal olefins an straight-chain, and they are mainly formed by the i nsertion reaction of l-butene with anti-Markovnikov addition rather than by isomerization of normal alpha-olefin. Paraffins are formed by hydrolysis o f metal-alkyl bond when the catalyst is deactivated with water.