Synthesis of low-molecular-weight poly-α-olefins using silicon-bridged zirconocene catalyst for lubricant basestock

The oily oligomers with low-molecular-weight, medium kinematic viscosity and high viscosity index are yielded through oligomerizations of higher α-olefins (1-hexene, 1-octene, 1-decene, 1-dodecene and 1-tetradecene) and co-oligomerization of 1-decene with 1-butene in the presence of the silicon-bridged Ph2Si(Cp)(9-Flu)ZrCl2 catalyst and the methylaluminoxane co-catalyst. The oligomerization activity is affected by the bulkiness and lateral size of monomer, and the viscosity of oligomer obtained. Through adding of 1-butene to 1-decene, the oligomerization activity is decreased, but viscosity index of oligomer obviously is increased. The highest co-oligomerization activity of 1-decene with 1-butene is presented at the temperature of 60 °C and Al/Zr molar ratio of 300. 1H and 13C NMR spectroscopy reveal that four types of vinylidene are existed in oligomers and the major olefinic bonds are internal disubstituted vinylidene, which are produced through 2,1-misinsertion and β-hydride elimination, or 2,1-misinsertion and rearrangement followed by β-hydride elimination. The chain termination of oligomerization of α-olefins favors chain transfer to the co-catalyst to produce saturated end group. The oligomerization pathways are summarized.