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首页> 外文期刊>RSC Advances >In situ X-ray absorption fine structure study on the polymerization of isoprene assisted by Nd-based ternary catalysts
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In situ X-ray absorption fine structure study on the polymerization of isoprene assisted by Nd-based ternary catalysts

机译：Nd基三元催化剂辅助异戊二烯聚合的原位 X射线吸收精细结构研究

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Nd-based ternary catalysts are widely used for the polymerization of isoprene in rubber industry, however structure information during the polymerization of isoprene as well as the catalytic mechanism are still ambiguous. In this paper, the in situ XAFS technique was used to extract the local atomic structure around the Nd center of the catalyst consisting of Nd(vers)3, AlEt3, and Al(iBu)2Cl. Theoretical calculations were used to verify the structure changes in the alkylation process. Four catalysts with different alkylaluminums {AlEt3, Al(nOct)3, Al(iBu)3, and Al(iBu)2H} were, respectively, used for the polymerization of isoprene. The results demonstrate that the substitution of Nd–C for Nd–O bonds is reasonable in the alkylation step. The structural evolutions in the alkylation and chlorination steps, as well as in the polymerization processes of isoprene are all similar for these Nd-based ternary catalysts with different alkylaluminum components. In the polymerization process of isoprene, there are only about 2 Nd–Cl bonds at 2.85 ? and 1–2 Nd–C bonds at 2.42 ? around the Nd centers which are in a monomer state. The Nd–C bonds can be attributed to the contribution of isoprene. This highly-opened structure of the Nd active centers activates greatly the catalytic activity of the Nd-based ternary catalysts. A conjectural catalytic mechanism for the polymerization of isoprene has been deciphered on the basis of the in situ XAFS results. This study is expected to be helpful for the improvement and application of the Nd-based ternary catalysts.
机译：Nd基三元催化剂在橡胶工业中广泛用于异戊二烯的聚合，但是异戊二烯聚合过程中的结构信息以及催化机理仍然不明确。本文采用原位 XAFS技术提取了由Nd（vers） 3 ，AlEt 3 和Al（ i Bu） 2 Cl。理论计算用于验证烷基化过程中的结构变化。四种具有不同烷基铝的催化剂（AlEt 3 ，Al（ n Oct）< small> 3 ，Al（ i Bu） 3 和Al（ i Bu） 2 H }分别用于异戊二烯的聚合。结果表明，在烷基化步骤中用Nd–C取代Nd–O键是合理的。对于具有不同烷基铝组分的这些基于Nd的三元催化剂，烷基化和氯化步骤以及异戊二烯的聚合过程中的结构演变都相似。在异戊二烯的聚合过程中，在2.85？处只有大约2个Nd–Cl键。和1–2 Nd–C键为2.42？处于单体状态的Nd中心附近。 Nd–C键可归因于异戊二烯的贡献。 Nd活性中心的这种高度开放的结构极大地激活了Nd基三元催化剂的催化活性。根据原位 XAFS结果，推测了异戊二烯聚合的推测催化机理。预期该研究将有助于Nd基三元催化剂的改进和应用。

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