Study On The Preparation Of A Novel High Active Spherical Catalyst For Propylene Polymerization

Catalyst system for propylene polymerization and polymerization process were the key to the development of polypropylene technology. However, the preparation of the catalyst system was strictly confidential, very few reports were found on the study of the preparation. In this paper, a novel spherical Ziegler-Natta catalyst system for polypropylene and its preparation were studied in detail, we also made some innovations in preparation conditions for the spherical support and the catalyst.By designing a new kind of magnetic autoclave vessel, we used a new method to prepare the spherical support, internal donors was added during the formation of the MgCl2/C2H5OH adduct, the optimal conditions were found:anhydrous MgCl2/anhydrous C2H5OH(molar ratio): 2.8~3.0temperature of the adduct formation: 120 internal donor/MgCl2(molar ratio): 0.2pre-dispersing speed of the stirrer: lOOOrpmultimate dispersing speed of the stirrer: 2000rpmtemperature of cooling point:-30*Cdispersing medium I / dispersing medium II (in volume): 1:1length of discharge pipe: 3mdiameter of the discharge pipe: I mm.The novel spherical catalyst particles were also synthesized in a new route, it was more favorable to obtain the catalyst under the following conditions:the TiCl4 was added two times during the preparation of the catalystTi/Mg (molar ratio) :80, the initial temperature: -20the ultimate temperature : 120 the reaction time: 2 hours.The behaviors of propylene polymerization under atmospheric pressure were investigated. We found that with the increase of the polymerization temperature, the activity of the catalyst increased and reached the optimum at 40 ,but had no significant influences on the isotactic index of polypropylene. With the increase of n (AlEt3) / n (Ti) , the activity of the catalyst reached a certain point and the isotactic index of polypropylene decreased gradually, and then the activity of the catalyst was decreased and the activity of the catalyst tended to be stabilized. Diphenyl-Dimethoxysilane(DDS) was used as external donor, the isotactic index of polypropylene produced by the catalyst can be adjusted sensibly. We also investigated the novel high active spherical catalyst in propylene bulk polymerization, the activity of the catalyst reached 106gPP/gTi, the isotacticity exceeded 95%(insoluble in the n-heptane), the diameter of the spherical polypropylene particle was in 1~2mm.