Research On PNP Ligands Contained Halogen For Ethylene Tetramerization

1-Octene is important chemical product and intermediate. It is widely used as a co-monomer for polyethylene, intermediates for plasticizer, fatty acid, detergent alcohols and oil dope. The ethylene copolymer with 1-octene as a co-monomer has better mechanical property, optical property, tear and impact resistance than those with 1-butene or 1-hexene as a co-monomer.According to the mechanisms of ethylene tetramerization, ten ligands were designed,synthesized in this study. The effect of ligands was studied in the catalytic system. The influence that ligand structure, reaction temperature, molar ratio of Al and Cr, molar ratio of PNP and Cr had on the 1-octene selectivity and catalytic activity was emphasized to study about four ligands in ten ligands. The best technological conditions were confirmed. Using N-(ortho-fluorophenyl)-diphoshinoamine as the ligand of ethylene tetramerization system,the catalytic activity can reach 2.52×10~6g/(mol Cr·h),the selectivity of 1-octene reaches 64.77% while molar ratio of Al and Cr is 300, molar ratio of PNP and Cr is 1.0 and reaction temperature is 60℃.When PNP ligands have different 2-position substituents of the N-aryl moiety, we find that the bigger the bulk of 2-position substituent of the N-aryl moiety is, the more the space is crowded, the punier the ability of attracting electron is, more 1-hexene is produced than 1-octene.Meta-substitued aryl PNP ligands show better catalytic activity than ortho ones and have more formation of 1-octene and PE. We can conclude that the structure of the ligand has important influence on the property of catalytic system. The catalytic activity, especially selectivity are determined more extent by the structure and coordination property of the ligand.