Study On Novel Ziegler-Natta Catalyst For Ethylene Gas Phase Polymerization

With the development of the ethylene gas phase polymerization technology,the M catalyst does not suit the condensed and super-condensed technology to produce polyethylene in the polymerization.So a new type catalyst based on catalyst synthesis reaction mechanism is introduced in this paper,and it is used for ethylene polymerization and copolymerization.The catalyst modified on the basis of M catalyst is also made from SiO₂,MgCl₂,TiCl₃ and THF, but some compound as electron donor compound is added in the preparation of the catalyst. Due to adding the compound,there is a weak chemical reaction of the electron donor with the silica supports,which could bind some active constituent.Because of the electron donor,on the one hand,the load of active constituent enhanced,which increased the activity of the catalyst;on the other hand,electron donor made the active constituent enter the tiny hole of the Silica carrier to enhance the bulk density of the polymers,and boost the quality of the polymer.On the preparation of the catalyst,the effects on different kinds of carrier,catalyst preparation conditions and electron donors on catalytic systems are studied.Hydrogen response and copolymerization performanceare also studied in the polymerization process.From the experiment results we know that the optimal catalyst preparation conditions are when the Mg/Ti moler ratio is 2.5,MgCl₂/SiO₂ mass ratio is 0.15,THF/Ti moler ratio is 2.0, the percentage of AlEt₂Cl is 47%,Al/Ti is 4.5 and electron donor A is used.The new type catalytic system for ethylene polymerization is much better than M catalytic system,which has not only improved the activity of the catalyst and good particle morphology of products, reduced fine power content of polymer product,but also has good hydrogen response and copolymerization performance.The catalyst is quasi-spherical,has good morphology,sents out heat uniformly and operates steadily.The new novel catalyst is very suitable for the condensation operation in Unipol gas phase fluidized bed polyethylene technology.