稀土催化聚合双烯烃的研究表明,不同稀土元素的催化活性极不一样,对此虽有不同的解释,但通常公认Sm、Eu等活性骤低,可归之于它们在制备催化剂过程中极易被烷基铝从三价还原到二价,又根据大部分具活性的其它稀土元素在催化体系中总是三价的事实,进而推断:只有在体系中能保持三价的稀土化合物方有产生活性的可能,二价化合物则不具活性。然而,由于二价稀土化合物,特别是除Sm、Eu之外的二价化合物难以制得,迄今为止并无直接的实验事实来判断这些推断是否正确。 Studies on rare earth-catalyzed polymerization of diolefins have shown that the catalytic activity of different rare earth elements is very different. Although different interpretations are made, the activity of Sm and Eu is generally recognized as being extremely low, which is attributed to their extremely ease in preparing the catalyst The fact that the aluminum alkyl is reduced from trivalent to divalent and based on the fact that most of the other active rare earth elements are always trivalent in the catalytic system leads to the conclusion that only the trivalent rare earth compounds in the system can be produced Activity is possible, the bivalent compounds are not active. However, since divalent rare earth compounds, especially divalent compounds other than Sm and Eu, are difficult to obtain, there is no direct experimental fact to date to judge whether these inferences are correct or not.