Synthesis Of Multi-Site Phosphorus Ligand-Iron Complex And Its Application In Ethylene Oligomerization

Linear?-olefins are widely used as raw materials in chemical industry.Ethylene selective oligomerization is an important development direction of linear?-olefin production process.Iron-based catalysts have become a research hotspot in ethylene selective oligomerization due to their advantages such as high activity,high selectivity and convenience to adjust their ligand structures.In the selective oligomerization of ethylene to produce?-olefin,many studies have shown that the ligand structure plays a leading role in the effect of the catalyst.Because of its strong coordination ability and unique spatial structure,most of the catalysts formed by multi-site PNP ligands have good catalytic effect.Therefore,the paper carried out the research on the generation of new catalysts by coordination of iron and PNP ligands and the detection of their properties.The specific work is as follows:(1)Multi-site PNP ligands L1?L4?L5?L6 were synthesized by using aminophenol and aminothiophenol substrates and diphenylphosphorus iron respectively.The structure of each ligand was determined by analysis means such as ¹H NMR and ¹³C NMR.(2)The ligand L1?L6 and Fe Cl₂·4H₂O were used to synthesize the corresponding complex R1?R6,which was used to catalyze ethylene oligomerization.The catalytic effects of the catalytic system composed of L1?L6 and the catalytic system composed of R1?R6were compared.(3)The above ligands are combined with iron salt and a co-catalyst methylaluminoxane(MAO)to form a system for catalyzing the oligomerization of ethylene.By changing the reaction conditions such as solvent,reaction temperature,Al/Fe molar ratio,ethylene pressure,cocatalyst,etc.,its influence on the catalytic reaction was investigated.Through comparative experiments,the effect of ligand structure on catalytic performance was investigated.It was revealed the catalytic activity of 12.23×10⁵g/(mol Fe·h)with 1-butene selectivity of 73.21%were obtained with L4/Fe(acac)₃/TEAC system at 45 ^oC,2.0 MPa of ethylene and Al/Fe molar ratio of 1000.