One-step preparation of efficient cuprous chloride catalyst for direct synthesis of trimethoxysilane

CuCl-based catalysts are the most commonly used catalysts for the “direct synthesis” of trimethoxysilane（M3）. CuCl species are sensitive to air and water, and are prone to oxidation deactivation. When CuCl is directly used as a catalyst, it needs to be purified before the utilization, and the operating conditions for the catalyst preparation are relatively harsh, requiring the inert gas environment. Considering a hightemperature activation step required for CuCl-based catalysts used for catalyzing synthesis of M3 to form active phase Cu-Si alloys（CuxSi） with Si powder, in this work, a series of catalysts for the “direct synthesis” of M3 were obtained by a one-step high-temperature activation of the mixture of stable CuCl2 precursors, activated carbon-reducing agent, and Si powder, simultaneously achieving the reduction of CuCl2 to CuCl and the formation of active phase CuxSi alloys of CuCl with Si powder. The prepared samples were characterized through various characterization techniques, and investigated for the catalytic performance for the “direct synthesis” of M3. Moreover, the operation conditions were optimized,including the activation temperature, catalyst dosage, Si powder particle size, and reaction temperature.The characterization results indicate that during the one-step activation process, the CuCl2 precursor is reduced to CuCl, and the resulting CuCl simultaneously reacts with Si powder to form active phases Cu3Si and Cu15Si4 alloys. The optimal catalyst Sacm（250, 0.8:10） exhibits a good catalytic activity with selectivity of 95% and yield of 77% for M3, and shows a good universality for various alcohol substrates. Furthermore, the catalytic mechanism of the prepared catalyst for the “direct synthesis” of M3 was discussed.