Deciphering the Promoting Effect of Zn on CuO for Dimethyldichlorosilane Production via the Rochow-Müller Reaction

Zinc (Zn) is commonly used as a promoter in Cu-based catalysts to boost the production of organosilane monomers during the Rochow-Müller reaction. However, the effect of Zn on the phase change of Cu-based catalysts in the reaction process is not yet fully understood. In this study, we prepared two Zn-modified CuO catalysts using simple ball milling (Zn–CuO) and physical mixing (Zn+CuO) methods. We found that adding Zn into CuO enhanced the adsorption of methyl chloride on the CuO surface, thereby promoting the sequential phase transformation of CuO to Cu2O and then to Cu and further to CuCl. Moreover, CuCl, as a key intermediate phase, could diffuse into Si powder and form Cu3Si under high-temperature conditions. Compared to CuO and Zn+CuO, Zn–CuO underwent a faster phase transformation, facilitating the generation of the active Cu3Si phase and enhancing the dimethyldichlorosilane selectivity and Si conversion. This study has clarified the role of the Zn promoter in the phase transformation of CuO catalysts in the Rochow-Müller reaction. Understanding this mechanism is crucial to designing more efficient catalysts.