Urchin-like ZnO microspheres synthesized by thermal decomposition of hydrozincite as a copper catalyst promoter for the Rochow reaction

Abstract

Urchin-like ZnO microspheres were successfully prepared by thermal decomposition of hydrozincite synthesized via homogeneous precipitation of zinc nitrate and urea in the presence of a nonionic surfactant polyethylene glycol. The synthesis conditions, such as reaction temperature and time, precursor concentration, and the amount of surfactant added, as well as the catalytic properties of urchin-like ZnO microspheres as promoters for a commercial copper catalyst in dimethyldichlorosilane synthesis were investigated. In addition, the formation mechanism of urchin-like microspheres from hydrozincite to ZnO was proposed. The ZnO samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and N₂ adsorption. It was found that zinc nitrate concentration and the amount of surfactant are the key factors that lead to the formation of urchin-like ZnO microspheres. These ZnO samples had BET surface areas of 16–30 m² g⁻¹ and an average diameter of 3–8 μm. Compared with commercial Zn microspheres and ZnO nanoparticles, urchin-like ZnO microspheres showed a better performance in dimethyldichlorosilane synthesis via the Rochow reaction due to their larger surface area, which created more interfacial contacts with the copper catalyst and active Cu₃Si species. The work is helpful for developing novel catalyst promoters and understanding the role of the promoter in the Rochow reaction.