BCl₃-Modified Ziegler-Natta Catalysts For Ethylene Polymerization

Polyolefins are the most widely used polymer materials during the world. Most of them are made by Ziegler-Natta catalysts. Therefore, development of new high-efficiency Ziegler-Natta Catalyst systems has always been the research hot spot between academia and industry. Because of the patent protection of many commercial catalystes, development of the catalysts with independent intellectual property rights is very important nowadays. In this thesis, a new series of Ziegler-Natta catalysts, modified by adding BCl3 and different kinds of internal donors (IDs), were conducted to ethylene polymerization. The results are summarized as follo wings:Four new IDs bearing different substituent group were designed and synthesized, which characterized by 1H and 13C NMR spectra. Attempting to synthesize the new ID with chelate structure but failed unfortunately. The products are with allyl group, which came from the elimination of dihalo-hydrocarbon.The influences of the alcohol types, addition methods and quantities of BCl3 on catalyst composition and polymerization performance were studied. The result showed that the catalyst with n-propanol-modified MgCl2 contained the highest Ti content, but its activity was not the best. There was significant influence on the catalyst composition and polymer properties using BCl3-modified MgCl2. With BCl3 content increasing, the Ti content and catalytic activity increased, and the highest catalytic activity was 2603 gPE/gTi·h·atm.The series of Ziegler-Natta catalysts were prepared by using the former IDs for ethylene polymerization under atmospheric pressure. With adding the IDs, the Ti content of catalysts decreased, which was related to the structure of IDs. The catalytic results showed that if adding the IDs with bulk substituents on benzyloxy, the catalytic activity slightly improved. However, the o-substituent of benzyloxy had little impact on catalytic activity. In addition, the influeces of polymerization time, Al/Ti ratio and polymerization temperature on ethylene polymerization was investigated. The result showed that using 4-tert-butyl-2-(butoxymethyl)methoxybenzene as ID, the highest activity was 2860gPE/gTi·h·atm at T= 50℃, n(Al)/n(Ti)=100, t= 1 h.