(381c) Nickel-Catalyzed Oligomerization of Di- and Trisubstituted Olefins

There is currently an abundance of light olefins produced from various refinery processes. For example, ~5% of fluid catalytic cracking (FCC) products are C₅ olefins, which is ~300 KBD (thousands of barrels per day) in the USA, and a large majority of these products are blended into gasoline. Chemistry that can upgrade the whole C₅ olefin stream to higher value products, like chemical intermediates, lubricant base stock or diesel fuel, is desirable. Although there are now many transition metal catalysts that can oligomerize alpha-olefins, these catalysts are typically less or unreactive towards internal and branched olefins, which are the primary components of the C₅ feed. In this talk, we will demonstrate the use of Nickel catalysts for the oligomerization of not only alpha-olefins, but also linear internal olefins, and most excitingly, di- and tri-substituted branched olefins. Mechanistic analysis indicates that catalysis proceeds through chain-insertion and chain-walking, which gives oligomer products which are more linear and less-branched, when compared with acid-catalysis. After studies on a variety of different C₅ olefins, we can predict the oligomer structure by abiding by two rules: (i) first olefin insertion and chain-walking to the C₅ terminus, and (ii) second olefin insertion where the C–C bond forms between the less substituted carbon and the terminus of the first inserted olefin (i.e. the metal bonds to more substituted carbon). Thus, with catalysts that abide by these rules, we can take traditionally low value feeds, like mixed C₅ olefins, and convert them into higher value products via oligomerization, most notably making less branched products than those that are achieved by acid catalysis.