Anilinoanthracenequinone Nickel Catalyzed Ethylene Oligomerization And Its Heterogenezation

Since the discovery of First-generation of Ziegler-Natta,the synthesis ofα-olefins via transition metal catalyzed by ethylene oligomerization have attracted extensive attention.Compared with the early-transition metal catalysts,the late transition metal catalysts have the advantages such as weak oxygen affinity,good stability,low production cost and simple synthesis.In this paper,aiming at the development of efficient late-transition metal catalysts for the ethylene oligomerization,（anilino）-anthraquinone nickel complex was selected to investigate their catalytic performance in the ethylene oligomerization in the presence of various aluminum compounds as the activation.The heterogenegation of the homogeneous nickel catalyst with high activity and high production selectivity was also conducted.Combined with the molecular simulation of density functional theory（DFT）,the effect factors for the ethylene oligomerization selectivity were studied from the aspects of reaction mechanism and path.First,we studied the ethylene oligomerization initiated by aniline anthraquinone nickel homogeneous system by changing the oligomerization conditions.The results showed that the nickel complex combined strong Lewis acidity such as Et Al Cl₂,Et₂Al Cl,MAO exhibits high catalytic activity(Et Al Cl₂:2.76×10~3kg·mol^-1·h^-1;Et₂Al Cl:3.1×10~3kg·mol^-1·h^-1;MAO:3.12×10~3kg·mol^-1·h^-1),while weak Lewis acidic ⁱBu₃Al or Et₃Al exhibited very low catalytic activity.The Ni-Et Al Cl₂system showed high butene selectivity（reached to 94%）with 70%of 1-butene with an Al/Ni ratio of 10 and ethylene pressure of 3Mpa at 40℃,although the catalytic activity was low(0.73×10~3kg·mol^-1·h^-1)in this oligomerization conditions.High catalytic activity(2.76×10~3kg·mol^-1·h^-1)was achieved by increasing the Al-Ni ratio（20）and decreasing the ethylene pressure（1.5MPa）with keeping the high butene selectivity（95%）.The homogeneous nickel catalyst was heterogeneized by using Et Al Cl₂supported Si O₂,and heterogeneous Ni-Et Al Cl₂/Si O₂also exhibited high catalytic activity(2.81×10~3kg·mol^-1·h^-1)and 1-butene selectivity（69%）.Second,we carried out molecular simulation by DFT with following the Cosee-Arlman ethylene oligomerization reaction mechanism to calculated the stable and transition Gibbs free energy of Ni-Et Al Cl₂catalyzed ethylene oligomerization pathways.Gibbs free energy change curves indicated that the catalyst has good 1-butene selectivity.The results of the reaction free energy of Ni-Et Al Cl₂with different oligomerization temperature and ligand substituent showed that the reaction energy barrier requires optimum temperature（40℃）for 1-butene selectivity.The isopropyl substituent on the anilino ligand showed higher energy barrier for the isomerization to increase the 1-butene selectivity,which further explains the effect of ligand substituent on the production selectivity in ethylene oligomerization.