Synthesis And Application Of Non- Metallocenic Early-transition Metal Catalysts For Olefin Coordination Polymerization

Polyolefin material is one of the most widely used materials in life and plays an important role in synthetic resin.Polyolefin catalyst is the key factor in the research of polyolefin material.The development of transition metal catalysts with high catalytic activity,producing polymers with well-defined structures,has attracteds more and more attention in recent years.This paper is based on the synthesis of the early-transition metal catalyst and the influence of polymerization conditions on the catalytic performance.In this paper,the early transition metal complexes with two different types of ligands were synthesized,and the structures were confirmed by NMR,FT-IR,elemental analysis and X-ray single crystal diffractions.The catalytic performances of catalysts were tested under different polymerization conditions.The main work of this thesis is summarized as follows:Salicylic aldehyde bimetallic titanium catalyst was synthesized.The catalytic activity of catalyst syn-Ti₂,anti-Ti₂ and mono-Ti was investigated under vary polymerization temperatures.The catalyst syn-Ti₂ has high catalytic activity and good thermal stability,and the polymer molecular weight distribution（PDI）is gradually reduced with the increase of temperature.Under polymerization conditions of 50°C and atmospheric ethylene press,syn-Ti₂,anti-Ti₂ and mono-Ti can achieve a copolymer with high insertion rate in ethylene and 1-hexene copolymerization,at the same time,syn-Ti₂ has the highest catalytic activity and PDI is the smallest.Molecular structure of complex syn-Ti₂ was determined by single-crystal X-ray diffraction and revealed that the titanium center forms a twisted octahedral structure around it.The catalytic performances of four monometallic Cr complexes with different steric effect were studied.It is found that increasing with polymerization temperature Cr² catalytic activity was increasied and PDI was decreased and 80°C was found to be the best reaction temperature.The amount of MAO has great influence on the activity of catalyst.With increasing the amount of MAO,catalytic activity was increased and PDI was decreased and Al/Cr=500 was found to be the optimum dosage.Under polymerization conditions of 80°C and Al/Cr=500,Cr¹-Cr⁴ catalytic performance was tested.The Cr⁴ with the highest space resistance has the highest catalytic activity and molecular weight.Molecular structure of complexes Cr³ and Cr⁴ was determined by single-crystal X-ray diffractions and revealed that the chromium center which is coordination with a single ligand forms a twisted octahedral structure around it.