Shu Guiqing, Zhao Jing, Zheng Xiu, Xu Mengdie, Liu Qi, Zeng Minfeng
Zhejiang Key Laboratory of Alternative Technologies for Fine Chemicals Process, College of Chemistry and Chemical Engineering, Shaoxing University, Shaoxing 312000, China.
Polymers (Basel). 2019 Apr 29;11(5):755. doi: 10.3390/polym11050755.
In this study, montmorillonite (MMT) was modified by intercalating polyethylene oxide (PEO) macromolecules between the interlayer spaces in an MMT-water suspension system. X-ray diffraction results revealed that the galleries of MMT were expanded significantly after intercalation of different loading of PEO. MMT/PEO 80/20 composite was chosen as the support platform for immobilization of Pd species in preparing novel heterogeneous catalysts. After immobilization of Pd species, the interlayer spacing of MMT/PEO (80/20) (1.52 nm) was further increased to 1.72 nm (Pd@MMT/PEO) and 1.73 nm (Pd@MMT/PEO), confirming the well-immobilization of the Pd species in the interlayer spaces of PEO-modified MMT. High-resolution transmission electron microscopy (HR-TEM) observation results confirmed that Pd nanoparticles were confined inside the interlayer space of MMT and/or dispersed well on the outer surface of MMT. The conversion of Pd to Pd species was evidenced by binding energy characterization with X-ray photo electron spectroscopy (XPS). The microstructure variation caused by the Pd immobilization was sensitively detected by positron annihilation lifetime spectroscopy (PALS) studies. The prepared Pd@MMT/PEO (0.2/80/20) catalytic composite exhibits good thermal stability up to around 200 °C, and it showed high activities for Heck reactions between aryl iodides and butyl acrylates and could be recycled for five times. The correlations between the microstructure and properties of the Pd@MMT/PEO catalytic composites were discussed.
在本研究中，通过在蒙脱石（MMT）-水悬浮体系的层间空间插入聚环氧乙烷（PEO）大分子对蒙脱石进行改性。X射线衍射结果表明，插入不同负载量的PEO后，MMT的层间距显著增大。选择MMT/PEO 80/20复合材料作为固定钯物种的载体平台，用于制备新型多相催化剂。固定钯物种后，MMT/PEO（80/20）的层间距（1.52 nm）进一步增加到1.72 nm（Pd@MMT/PEO）和1.73 nm（Pd@MMT/PEO），证实钯物种很好地固定在PEO改性MMT的层间空间。高分辨率透射电子显微镜（HR-TEM）观察结果证实，钯纳米颗粒被限制在MMT的层间空间内和/或很好地分散在MMT的外表面。通过X射线光电子能谱（XPS）的结合能表征证明了钯向钯物种的转化。通过正电子湮没寿命谱（PALS）研究灵敏地检测到了钯固定化引起的微观结构变化。制备的Pd@MMT/PEO（0.2/8o/20）催化复合材料在高达约200℃时表现出良好的热稳定性，并且对芳基碘化物和丙烯酸丁酯之间的Heck反应显示出高活性，并且可以循环使用五次。讨论了Pd@MMT/PEO催化复合材料的微观结构与性能之间的相关性。
