Heterocene Catalysts and Reaction Temperature Gradient in Dec-1-ene Oligomerization for the Production of Low Viscosity PAO Base Stocks

Hydrogenated oligomers of higher α-olefins (primarily, dec-1-ene) with uniform structure represent high-quality poly-α-olefin oil (PAO) base stocks. High yields of lightweight dec-1-ene oligomers (DP n = 3–4) can be achieved by using 5,10-dihydroindeno­[1,2-b]­indole-based zirconium ansa-complexes, “heterocenes”. Unusual catalytic behavior of heterocenes served as a starting point for the present study, during which new, more synthetically available and active heterocene precatalysts were synthesized, and a novel oligomerization method, based on a reaction temperature gradient, was developed. A gradual decrease of the oligomerization temperature as dec-1-ene was consumed resulted in decreased dimer formation (down to 10%) and increased oligomer yields (up to 84%). After hydrogenation, low- and medium-viscosity PAO base oils with uniform structure and high viscosity indexes were obtained.