Nanosized Pd assembled on superparamagnetic core–shell microspheres: Synthesis, characterization and recyclable catalytic properties for the Heck reaction

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 (TEM), N2 adsorption–desorption 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/Fe3O4@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/Fe3O4@γ-Al2O3 catalysts exhibited good catalytic activity and recyclability. With Pd/Fe3O4@γ-Al2O3 (0.021 mol%) catalyst, the bromobenzene conversion and product yield reached about 96.8% and 91.2%, respectively, at 120 °C 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/Fe3O4@γ-Al2O3 catalysts.

The magnetically recyclable Pd/Fe3O4@γ-Al2O3 catalysts with nanosized Pd assembled on core–shell microspheres were synthesized and the magnetic catalysts shown good activity and reusability for the Heck coupling reaction.Figure optionsDownload as PowerPoint slide