A series of magnetically recyclable Pd/Fe3O4@γ-Al2O3 catalysts were synthesized using the superparamagnetic Fe3O4@γ-Al2O3 core-shell microspheres as the supporter and nano-Pd particles assembled on γ-Al2O3 shell as...A series of magnetically recyclable Pd/Fe3O4@γ-Al2O3 catalysts were synthesized using the superparamagnetic Fe3O4@γ-Al2O3 core-shell microspheres as the supporter and nano-Pd particles assembled on γ-Al2O3 shell as the active catalytic component. The structure of the catalysts was characterized by X-ray diffraction （XRD）, transmission electron microscopy iTEM）, N2 adsorptiondesorption and vibrating sample magnetometer （VSM）. The catalytic activity and the recyclability properties of the catalysts for the Heck coupling reaction with aryl bromides and the olefins were investigated. The results show that the microspheres of the magnetic Pd/Fe304@γ-Al2O3 catalysts were about 400 nm and the nano-Pd particles assembled on γ-Al2O3 shell were about 3-4 nm in size. The saturation magnetization （MS） of the magnetic catalysts was sufficiently high to allow magnetic separations. In the Heck coupling reactions, the magnetic Pd/Fe304@γ-Al2O3 catalysts exhibited good catalytic activity and recyclability. With Pd/Fe304@γ-Al2O3 （0.021 mol%） catalyst, the bromobenzene conversion and product yield reached about 96.8% and 91.2%, respectively, at 120℃ and in 14 h. After being recycled for six times, the conversion of bromobenzene and the recovery of the catalyst were about 80% and 90%, respectively. The nano-Pd particles were kept well dispersed in the used Pd/Fe304@γ-Al2O3 catalysts.展开更多
提出了一种在水树缺陷内生成纳米级TiO2颗粒的修复液及修复方法,并针对该修复液的修复机制及绝缘增强机制进行了讨论。采用水针法在交联聚乙烯(XLPE)电缆样品中制造水树缺陷,并对已生成水树的样品进行了基于钛酸酯类催化的硅氧烷修复液...提出了一种在水树缺陷内生成纳米级TiO2颗粒的修复液及修复方法,并针对该修复液的修复机制及绝缘增强机制进行了讨论。采用水针法在交联聚乙烯(XLPE)电缆样品中制造水树缺陷,并对已生成水树的样品进行了基于钛酸酯类催化的硅氧烷修复液注入式修复,发现其绝缘性能得到显著提高,甚至击穿电压指标明显优于新电缆。基于扫描电子显微镜(scanning electron microscope,SEM)、X射线光电子能谱分析(X-ray photoelectron spectroscopy,XPS)和红外光谱分析,证明被修复样品击穿通道内有纳米级TiO2颗粒存在。通过对钛酸酯类催化剂水解反应的生成物研究,证明了该催化剂水解后生成纳米级TiO2颗粒。基于这一发现,提出了相应的绝缘增强机制及作用模型,认为分散的纳米级TiO2颗粒有效抑制了通道内由于局部放电产生的烧蚀损伤,从而增强了电缆的绝缘性能,提高了电缆的击穿电压。展开更多
基金Financial support from the National Natural Science Foundation of China (No.21173018)
文摘A series of magnetically recyclable Pd/Fe3O4@γ-Al2O3 catalysts were synthesized using the superparamagnetic Fe3O4@γ-Al2O3 core-shell microspheres as the supporter and nano-Pd particles assembled on γ-Al2O3 shell as the active catalytic component. The structure of the catalysts was characterized by X-ray diffraction （XRD）, transmission electron microscopy iTEM）, N2 adsorptiondesorption and vibrating sample magnetometer （VSM）. The catalytic activity and the recyclability properties of the catalysts for the Heck coupling reaction with aryl bromides and the olefins were investigated. The results show that the microspheres of the magnetic Pd/Fe304@γ-Al2O3 catalysts were about 400 nm and the nano-Pd particles assembled on γ-Al2O3 shell were about 3-4 nm in size. The saturation magnetization （MS） of the magnetic catalysts was sufficiently high to allow magnetic separations. In the Heck coupling reactions, the magnetic Pd/Fe304@γ-Al2O3 catalysts exhibited good catalytic activity and recyclability. With Pd/Fe304@γ-Al2O3 （0.021 mol%） catalyst, the bromobenzene conversion and product yield reached about 96.8% and 91.2%, respectively, at 120℃ and in 14 h. After being recycled for six times, the conversion of bromobenzene and the recovery of the catalyst were about 80% and 90%, respectively. The nano-Pd particles were kept well dispersed in the used Pd/Fe304@γ-Al2O3 catalysts.
文摘提出了一种在水树缺陷内生成纳米级TiO2颗粒的修复液及修复方法,并针对该修复液的修复机制及绝缘增强机制进行了讨论。采用水针法在交联聚乙烯(XLPE)电缆样品中制造水树缺陷,并对已生成水树的样品进行了基于钛酸酯类催化的硅氧烷修复液注入式修复,发现其绝缘性能得到显著提高,甚至击穿电压指标明显优于新电缆。基于扫描电子显微镜(scanning electron microscope,SEM)、X射线光电子能谱分析(X-ray photoelectron spectroscopy,XPS)和红外光谱分析,证明被修复样品击穿通道内有纳米级TiO2颗粒存在。通过对钛酸酯类催化剂水解反应的生成物研究,证明了该催化剂水解后生成纳米级TiO2颗粒。基于这一发现,提出了相应的绝缘增强机制及作用模型,认为分散的纳米级TiO2颗粒有效抑制了通道内由于局部放电产生的烧蚀损伤,从而增强了电缆的绝缘性能,提高了电缆的击穿电压。
