Direct synthesis of tetraalkoxysilanes in a high-pressure mechanochemical reactor

Abstract

We report the results of studies on the direct synthesis of tetraalkoxysilanes from alcohols and metallic silicon in a high-pressure mechanochemical reactor. The effect of the following factors on the process was considered: temperature (100–250 °C), amount of catalyst (0–20 wt%), type of catalyst, and type of the alcohol used in the synthesis. A silicon conversion of 90% with a selectivity of 94% with respect to a tetraalkoxysilane can be attained under optimal conditions. The studies showed that the temperature of the direct synthesis of alkoxysilanes was the lowest of the values reported to date (100 °C). Under these conditions, a silicon conversion of 77% and a selectivity of 98% with respect to a tetraalkoxysilane can be attained. It was shown that CuCl (20 wt%) exhibited the highest activity among copper-based catalysts, including CuF₂, CuCl, CuBr, CuI, CuO, and Cu₂O. In addition to MeOH, such alcohols as EtOH, n-BuOH, and EtO(CH₂)₂OH were used. The contact masses (CMs) sampled after 15 and 25 minutes and after reactions at 150, 200, and 250 °C were studied using SEM-EDX, PXRD, and XPS.