The Structural Evolution of the CuCl Catalyst during the Direct Synthesis of Trimethoxysilane

CuCl is a commonly used copper-based catalyst for the direct synthesis of trimethoxysilane (M3), which is the primary method for industrial production of M3 monomers. However, the effect of the CuCl catalyst on the phase transitions during the direct synthesis process is not well understood. In this study, we prepared four model CuCl catalysts (CuCl-Y, CuCl-10 min, CuCl-0.5h, and CuCl-1h) by varying the ball-milling duration. Among these, the unmilled CuCl catalyst exhibited the highest M3 selectivity and silicon conversion at 240 °C. During the high-temperature activation stage, the CuCl catalysts underwent phase transformation to form Cu3Si and active Cu species, both of which are catalytically active. When methanol was introduced, the Cu3Si phase contributed to the formation of M3. These results deepen our understanding of the reaction mechanism and offer guidance for designing more efficient catalysts.