The Effect Of Electron Donor On The Polymerization Of Olefins In Supported Ziegler-Natta Catalysts

Polyolefins are the most widely used polymer materials nowadays,owing to their combination of outstanding physical properties,excellent chemical resistances and especially low costs.Therefore,development of the catalytic systems for polyolefins has become the research hotspot in both industry and academia.As the most widely used catalyt,Ziegler-Natta catalysts have been rapidly developed in the decades.In this thesis,we designed and synthesized several new internal donors?IDs?for Ziegler-Natta catalysts and investigated ethylene and propylene polymerization by using these Ziegler-Natta catalysts.The results are summarized as followings.Seven new asymmetric IDs bearing different substituents and three tetrahydrofuran or furan derivatives were designed and synthesized,which characterized by 1H and 13 C NMR spectra.The results showed that the chain length of substituents greatly affect the yield,which decreased with lengthening the chain length.The series of Ziegler-Natta catalysts were prepared by using the former IDs for ethylene polymerization.The influences of types and quantities of IDs,types and quantities of aluminum alkyl,polymerization time and doping SiO₂ on ethylene polymerization were studied.With adding the IDs,the catalytic activities increased obviously.The substituents of IDs show a great influence on the catalytic activity.When the substituent R¹ at ortho position of phenoxy is t-butyl,the activities of ethylene polymerization decreased with lengthening the alkoxy chain length?R³?.When the substituent R¹ at ortho position of phenoxy is hydrogen,the activities of ethylene polymerization increased with lengthening the alkoxy chain length?R³?.That can be attributed to the both the electronic effect and steric effect.By using composite support MgCl2/Si O₂,the polyethylene with relatively narrow particle size distribution,that was mainly the diameter of about 100 ?m,was obtained.In addition,the influence of polymerization time,Al/Ti ratio and the types and quantities of co-catalyst on ethylene polymerization was investigated.The results showed that by using 4-tert-butyl-2-?octyloxomethyl?methoxybenzene as ID?n?ID?:n?Mg?= 0.2?and AlEt₃ as cocatalyst?n?Al?:n?Ti?= 150?,the highest activity was 4994.1 g·PE/g·Ti·h at 1 atm,and 13613 g·PE/g·Ti·h at 6 atm.By changing the reaction conditions,the Ziegler-Natta catalysts with different IDs were prepared at low temperature for propylene polymerization.The results showed that the addition of IDs could significantly improve the isotacticity of polypropylene.In addition,the influence of types and quantities of external donors?EDs?,quantities of co-catalysts and so on were investigated.The results showed that by using phenyl trimethoxysilane as ED?n?ED?:n?Ti?= 5?and n?Al?:n?Ti?= 150,the highest isotactic polypropylene was obtained?91.5 %?with the catalytic activity 510g·PP/g·Ti·h.