Study On(Co-) Polymerization Of Ethylene/1-Hexene Catalyzed By[N,Si,N,P] Non-metallocene Catalysts Without Cocatalyst Combining HSAB And DFT Analysis

Polyolefins are widely used in various industries such as automobile manufacturing,medical equipment,food packaging,and pipe construction due to its excellent physical and chemical properties.The demand in society is also increasing.At present,China's polyolefin industry mainly produces low-level homopolymer products,and most high-level polyolefin products rely on imports.Therefore,the development of high-performance polyolefin elastomers,polar copolymers and other products has become the focus of research in this field.The development of olefin products mainly depend on the innovation of catalysts.In this paper,six kinds of[N-Si-N-P]titanium-based non-metallocene catalysts and three kinds of[N-Si-N-P]nickel-based non-metallocene catalysts were designed and synthesized.The(co-)polymerization conditions for ethylene and ethylene/1-hexene were optimized.The activity of Cat.5 at the polymerization temperature of 60?,the ethylene pressure of 0.05MPa can be up to 2.83 × 105 g Polymer/(molTi·h)-1 without cocatalyst,the activity of Cat.8 at the polymerization temperature of 60?,the ethylene pressure of 0.05MPa can be up to 2.13 × 105 g Polymer/(molTi·h)-1 without cocatalyst.The copolymerization of ethylene/1-hexene was carried out on Cat.5 and Cat.8 respectively.Cat.5 has the highest monomer insertion rate of 5.24%when the amount of 1-hexene monomer was 12 ml and Cat.8 has the highest monomer insertion rate of 4.97%when the amount of 1-hexene monomer was 12 ml.The mechanism of ethylene insertion in the catalyst was explored using HSAB theory and DFT analysis.The HSAB theory showed that the catalyst with polyfluoro ligands was easier to insert ethylene,the DFT calculation also showed the lower energy barrier of the catalyst with polyfluoro ligands,which makes the reaction easier.It can also be seen from the DFT result that ethylene is easier to react with one of the M-C bonds in the complex,the energy barrier is lower and the reaction is easier to proceed.Compared to the substituents of Me and H,these catalysts consisting of ligands having many F atoms on phenylamine ring for ethyleng homopolymerization and ethylene/1-hexene copolymerization,polyolefins with much higher molecular weight were obtained.