Coadsorption model for first-principle description of roles of donors in heterogeneous Ziegler–Natta propylene polymerization
Coadsorption model for first-principle description of roles of donors in heterogeneous Ziegler–Natta propylene polymerization
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DOI：
10.1016/j.jcat.2012.06.001
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发表时间：
2012-09
影响因子：
7.3
通讯作者：
Toshiaki Taniike;M. Terano
中科院分区：
文献类型：
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作者：
Toshiaki Taniike;M. Terano
采用周期密度泛函方法研究了非均相Ziegler-Natta催化剂丙烯聚合过程中给电子体的空间位阻和电子效应.结果表明，TiCl 4以单核物种的形式优先吸附在MgCl 2（110）表面，施主与TiCl 4的共吸附在热力学上是可行的.供体在（110）面上的共吸附增强了Ti单核物种的电子密度，并在空间上转移了潜在的C2对称性，将最初的非特异性单核物种转化为等特异性单核物种。苯甲酸乙酯（EB）的最近的共吸附不仅在空间上诱导了钛单核物种的等专一性，而且在静电上提高了丙烯插入的区域专一性。此外，EB防止空间要求高的链转移到丙烯，增加生产的聚丙烯的分子量。因此，从理论上推导出的“共吸附模型”与各种实验已知的事实高度一致，并认为是有用的从头计算预测的新的施主结构。
Systematic periodic density functional calculations were conducted to clarify the mechanism for donors to exert steric and electronics influences on propylene polymerization using heterogeneous Ziegler–Natta catalysts. It was concluded that TiCl4preferentially adsorbs as mononuclear species on the MgCl2(110) surface, and the coadsorption of donors with it is energetically viable. The coadsorption of donors on the (110) surface reinforces the electron density of the Ti mononuclear species and sterically transfers the underlying C2symmetry to convert the originally aspecific mononuclear species into isospecific one. The nearest coadsorption of ethylbenzoate (EB) not only sterically induces the isospecificity of the Ti mononuclear species but also electrostatically improves the regiospecificity in propylene insertion. In addition, EB prevents sterically demanding chain transfer to propylene, increasing the molecular weight of the produced polypropylene. Thus theoretically derived “coadsorption model” is highly consistent with a variety of experimentally known facts and believed to be useful for the ab initio prediction of new donor structures.