Selective Direct Synthesis of Trialkoxysilanes in a Packed Bed Flow Tubular Reactor

Trialkoxysilanes were synthesized in a packed bed flow tubular reactor by the reaction of silicon and alcohol in the presence of a variety of copper catalysts. The effect of key parameters, which affect the silicon conversion rates and selectivity for the desired trialkoxysilanes, were investigated and optimized using ethanol as the model reagent. The study was extended to the other alcohols namely methanol, n-propanol, and n-butanol. Copper catalysts which were tested in the alkoxylation reaction included CuCl, Cu(OH)2, CuO, and CuSO4; with CuCl showing the most activity while the uncatalysed reaction resulted in negligible reaction rates. High temperature catalyst preheating (>500 °C) resulted in a lower rate of reaction than when lower temperatures were used (<350 °C). The optimum reaction temperature range and alcohol flow rate were 230–240 °C and 0.1 mL/min, respectively. The reaction was deduced to be best described by the first-order kinetic model. The effect of alcohol (C1–C4) on the reaction revealed that conversion and selectivity generally decrease with an increase in carbon chain length. Ethanol showed the highest selectivity (97%) and conversion (64%) as compared to other alcohols studied, showing that it was the most efficient and stable alkoxylation alcohol for this reaction.