聚合
催化作用
材料科学
化学工程
扫描电子显微镜
烯烃纤维
茂金属
甲基铝氧烷
聚合物
高分子化学
化学
复合材料
有机化学
工程类
作者
Maximilian J. Werny,D. Müller,Coen Hendriksen,Robert Chan,Nic Friederichs,Christian Fella,Florian Meirer,Bert M. Weckhuysen
出处
期刊:Chemcatchem
[Wiley]
日期:2022-10-06
卷期号:14 (21)
被引量:1
标识
DOI:10.1002/cctc.202200067
摘要
Abstract Strict morphological control over growing polymer particles is an indispensable requirement in many catalytic olefin polymerization processes. In catalysts with mechanically stronger supports, e. g., polymerization‐grade silicas, the emergence of extensive cracks via the sectioning fragmentation mechanism requires severe stress build‐up in the polymerizing catalyst particle. Here, we report on three factors that influence the degree of sectioning in silica‐supported olefin polymerization catalysts. Laboratory‐based X‐ray nano‐computed tomography (nanoCT) and focused ion beam‐scanning electron microscopy (FIB‐SEM) were employed to study catalyst particle morphology and crack propagation in two showcase catalyst systems, i.e., a zirconocene‐based catalyst (i.e., Zr/MAO/SiO 2 , with Zr=2,2’‐biphenylene‐bis‐2‐indenyl zirconium dichloride and MAO=methylaluminoxane) and a Ziegler‐Natta catalyst (i.e., TiCl 4 /MgCl 2 /SiO 2 ), during slurry‐phase ethylene polymerization. The absence of extensive macropores in some of the catalysts’ larger constituent silica granulates, a sufficient accessibility of the catalyst particle interior at reaction onset, and a high initial polymerization rate were found to favor the occurrence of the sectioning pathway at different length scales. While sectioning is beneficial for reducing diffusion limitations, its appearance in mechanically stronger catalyst supports can indicate a suboptimal support structure or unfavourable reaction conditions.
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