47,49Ti solid-state NMR and DFT study of Ziegler-Natta catalyst: Adsorption of TiCl4 molecule onto the surface of MgCl2
47,49Ti solid-state NMR and DFT study of Ziegler-Natta catalyst: Adsorption of TiCl4 molecule onto the surface of MgCl2
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DOI：
10.1016/j.jpcs.2019.109088
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发表时间：
2019-12
影响因子：
4
通讯作者：
T. Iijima;T. Shimizu;A. Goto;K. Deguchi;T. Nakai;R. Ohashi;Masayoshi Saito
中科院分区：
文献类型：
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作者：
T. Iijima;T. Shimizu;A. Goto;K. Deguchi;T. Nakai;R. Ohashi;Masayoshi Saito
在钛基Ziegler-Natta催化剂（ZNC）中，MgCl 2载体的哪一个侧面吸附了钛物种，从而成为催化聚合的活性中心，存在着不同的观点。本文采用沿着的47，49 Ti固体核磁共振（NMR）谱和密度泛函理论（DFT）计算研究了TiCl_4吸附在MgCl_2表面的局域结构。采用Czjzek模型模拟了球磨20 h后TiCl 4/MgCl 2加合物样品的魔角旋转NMR谱，发现球磨前后样品的谱峰发生了展宽和位移.通过密度泛函理论（DFT）计算了模型分子TiCl 4、2 TiCl 4和Ti 2Cl 8吸附在MgCl 2（110）、（104）和（104）阶缺陷面上的电场梯度和化学屏蔽张量.通过比较所获得的NMR参数，将研磨样品的47，49 Ti NMR谱归属于吸附在MgCl 2的（104）表面上的TiCl 4，其可能不是吸附的主要组分。
In Ti-based Ziegler-Natta catalysts (ZNCs), disagreements exist concerning which lateral surface of the MgCl2support adsorbs Ti species so as to be an active site for the catalysis of polymerization. In the present paper, we investigated the local structure of TiCl4adsorbed onto the surface of MgCl2by47,49Ti solid-state nuclear magnetic resonance (NMR) spectra at 21.8 T along with density functional theory (DFT) calculations. The magic-angle-spinning NMR spectrum of the TiCl4/MgCl2adduct sample prepared by 20 h of milling, which exhibited broadened and shifted peaks compared to that of the sample without milling, was simulated by a Czjzek model considering the distribution of quadrupole interaction parameters. The electric field gradient and chemical shielding tensors of49Ti were obtained via DFT calculations for model molecules of TiCl4, 2TiCl4, and Ti2Cl8adsorbed onto the (110), (104), and (104)-step defect surfaces of MgCl2. By comparing the obtained NMR parameters, the47,49Ti NMR spectrum of the milled sample was assigned to TiCl4adsorbed onto the (104) surface of MgCl2, which may not be a principal component of adsorption.