DNBP给电子体构象分析及在Ziegler-Natta丙烯聚合中作用机理研究

首次采用TINKER构象搜索和DFT结构优化相结合方法,基于对Ziegler-Natta丙烯聚合催化体系邻苯二甲酸正丁酯(DNBP)给电子体快速搜索出的1 023种构象,筛选出其优势构象,减少了给电子体初始稳定结构搭建模型的盲目性和随机性.采用DFT方法,对DNBP两种构象与MgCl2载体相互作用及丙烯插入立体选择性机理进行了研究.结果表明,DNBP构象影响其在MgCl2表面的吸附,s-顺、反式构象可以单齿、桥连和螯合方式吸附在MgCl2(110)表面;s-顺、顺式仅存在桥连吸附.双氯原子缺陷载体模型上TiCl4吸附的稳定性高于DNBP,成为可能的活性中心;给电子体对活性位的作用与其吸附方式有关,DNBP以桥连方式吸附在Ti的邻位,可将无规活性中心有效转化为等规活性中心,而螯合方式不能改善催化剂的立体结构和区域选择性.

Conformational analysis of donor DNBP in Ziegler-Natta propylene polymerization

A combination of TINKER and DFT method was firstly used for conformational searches and optimization of di-n-butyl phthalate (DNBP), which is a commercial donor in Ziegler-Natta catalyst for the propylene polymerization. 1023 DNBP conformations were quickly found, suggesting it was an effective method to reduce the blindness and randomness in the donor initial modeling. Geometry optimization of various conformations, as well as the interaction between DNBP and MgCl2 support and the effect of DNBP on the propylene enantioselective insertion have been studied by DFT method. The results indicated that the conformation played an important role on the absorption of DNBP on MgCl2 surface. The s- cis, trans conformation could adsorb on MgCl2 (110) surface in the monodentate, bridge and chelate modes, while the s-cis,cis one only adsorb in the bridge mode. The defective site with more stable adsorption of TiCl4 than that of DNBP might be the active center. The adsorption of DNBP in bridge mode on the vicinal position of Ti could effectively transform the atacticactive site into the isotactic one. However, when DNBP adsorbed in the chelate mode, the isospecificity and regioselectivity of catalystcould not be improved.