Preparation Of Linear Long-Chain α-olefins From Ethylene Oligomerization Catalyzed By New Bis(β-ketiminato) Zirconium Catalysts

Linear α-olefins(LAO)usually refer to linear terminal olefins with four or more carbon atoms,which are important organic chemical raw materials and can be widely applied in many fields such as surfactants,plasticizer alcohols,high-grade lubricating oils,lubricating oil additives and as co-monomers for advanced polyolefin materials.However,lower molecular weight and presence of by-products limit its further application.In this dissertation,a series of novel bis(β-ketiminato)zirconium complexes have been synthesized and characterized to prepare linear long-chain αolefins through oligomerization of ethylene based on the concept of structure design for ethylene oligomerization catalyst and preliminary research work of our research group.1.By introducing substituents with different electronic effect and steric bulk into the ortho-or para-position of the N-aryl moieties of β-ketimine ligands,several novel Zr complexes for the oligomerization of ethylene were synthesized in a simple and efficient way.These complexes have been confirmed to adopt a cis Ⅱ configuration as the most stable form by single crystal X-ray diffraction.And they can catalyzed ethylene oligomerization to give linear α-olefins by activation of cocatalyst.2.Activated with different cocatalysts,these novel Zr complexes showed high activities(up to 5.12×10~6 g/(molZr·h))for ethylene oligomerization compared with the Zr complex bearing a benzyl substituent and generated a high yield(close to 100%)of the long-chain linear α-olefins with terminal double bonds.For Zr-catalyzed oligomerization of ethylene in the present of dried methylalumoxane(dMAO)as cocatalyst,the catalytic activity,molecular weights and molecular weight distributions of oligomers can be controlled within a wider range by turning ligand structures.3.Studies on ethylene oligomerization with Zr complexes under different conditions indicated that there are no significant changes in the molecular weights and molecular weight distributions of ethylene oligomers with an increase in Al/Zr molar ratio as well as ethylene pressure.Besides,high temperature NMR test of oligomers studies show that there is not the generation of by-products except for linear long-chainα-olefins via chain transfer to monomer during ethylene oligomerization.Additionally,these Zr complexes maintained relatively high activities in ethylene oligomerization even when the temperature was elevated to 75℃ for extended reaction time,indicating excellent stability and high temperature resistance.