超支化双吡啶亚胺铬催化剂的合成及催化乙烯齐聚性能

以1.0代(G)超支化大分子(C38H51N9O2)为配体骨架,2-氯-4-甲基吡啶和CrCl3(THF)3为原料,依次经过取代和配合反应合成了一种超支化双吡啶亚胺配体及其铬催化剂。利用紫外-可见光谱(UV-Vis)、傅里叶变换红外光谱(FT-IR)、电喷雾电离质谱(ESI-MS)、核磁共振氢谱(1HNMR)和元素分析等方法对其进行表征。结果与理论设计预期一致。考察了反应温度、乙烯压力、Al与Cr摩尔比(n(Al)/n(Cr))、溶剂及助催化剂种类等因素对催化剂催化乙烯齐聚性能的影响。结果表明,以甲苯为溶剂,甲基铝氧烷(MAO)为助催化剂,当反应温度为45℃,乙烯压力为4MPa,n(Al)/n(Cr)=300,催化剂用量为7μmol时,活性可达1.32×10^5g/(mol(Cr)·h),C6和C8的选择性为59.30%。

Synthesis and Ethylene Oligomerization Behavior of Hyperbranched Bispyridineimine Chromium Catalyst

A new hyperbranched bispyridineimine ligand was derived from 1.0 generation hyperbranched macromolecules and 2-chloro-4-methylpyridine through substitution reaction. Multinuclear chromium complex was synthesized from the reaction with chromium(Ⅲ) chloride tetrahydrofuran complex. The structure of hyperbranched bispyridineimine ligand and chromium complex were characterized by ultraviolet-visible spectrophotometer(UV-Vis), Fourier transform infrared spectroscopy(FT-IR), proton nuclear magnetic resonance(¹H NMR), and electrospray ionization mass spectrometer(ESI-MS) and elemental analysis. The result accords with what we designed theoretically. The novel hyperbranched chromium complex was evaluated as catalyst precursor in the ethylene oligomerization, using methylaluminoxane(MAO) as an activator. At the same time, we investigated the effects of reaction temperature, ethylene pressure, Al/Cr molar ratio, co-catalysts and solvents on the catalytic activity and product selectivity. The oligomerization results show that the activity of the catalyst is 1.32×10⁵ g/(mol(Cr)·h) and the selectivity for C₆ and C₈ reaches up to 59.30% at 45 ℃ and 4 MPa, Al/Cr molar ratio of 300 and 7 μmol catalyst loading with MAO as co-catalyst in toluene.