Tandem Catalytic Systems: One Catalyst Combined with Two Different Activators for Preparing Branched Polyethylene with Ethylene as Single Monomer

摘要

Branched polyethylene such as linear low density polyethylene is more attractive because of its broad range of commodity applications and scientific value in preparing polyolefin with well-defined structure. It is commonly produced on industrial scales by the copolymerization of ethylene with R-olefin comonomer which comes from ethylene oligomerization. Since 1980s, many researches have been developed a new technique “tandem catalysis”, which is a one-step method for preparing branched polyethylene from the single monomer of ethylene by the action of oligomerization and copolymerization catalyst precursors with one activator in the same reactor.1 Since the linear R-olefins are formed in situ, the separation, transportation and storage of the comonomer are eliminated. So tandem catalysis could be a more economical way of preparing branched polyethylene. Up to now, various combinations of catalysts have been employed in tandem catalysis, such as two different Ziegler-Natta catalysts,1,2 Ziegler-Natta catalyst/homogeneous catalyst,3 or two or three different homogeneous catalysts.