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考察了TiCl_4-AlC_2H_5Cl_2催化体系中钛的价态对乙烯高聚或低聚的影响。Ti(Ⅳ)与Ti(Ⅲ)形成不同的活性中心,乙烯在Ti(Ⅳ)活性中心上生成低聚物,在Ti(Ⅲ)活性中心上生成高聚物。当这两种活性中心共存时互不干扰,同时生成相应的低聚物和高聚物。链转移速度在Ti(Ⅳ)活性中心上比在Ti(Ⅲ)上至少大两个数量级,而链增长速度则在同一个数量级。说明在此体系中,由于价态变化而改变的β-H转移速度是决定生成高聚物或低聚物的主要原因。
The effect of titanium valence on the polymerization or oligomerization of ethylene in TiCl 4 -AlC 2 H 5 Cl 2 catalytic system was investigated. Ti (Ⅳ) and Ti (Ⅲ) form different active centers. Ethylene produces oligomers on the active sites of Ti (Ⅳ) and polymers on Ti (Ⅲ) active sites. When the two active centers co-exist without interfering with each other, while generating the corresponding oligomers and polymers. The rate of chain transfer is at least two orders of magnitude greater than that of Ti (III) in the active center of Ti (IV), while the rate of chain growth is in the same order of magnitude. This shows that in this system, the β-H transfer rate, which is changed due to valence changes, is the main reason for the formation of polymers or oligomers.