Effect of Al and Ca addition on the copper catalysed formation of silanes from Si and CH3Cl Original Research Article

The effect of Al and Ca addition on formation of silanes in the Rochow Direct Process is described and discussed. The catalysts are evaluated in a stirred-bed microreactor using on-line gas chromatographic analysis. The formation of silanes from the reaction of Si and CH3Cl is studied using a copper catalyst in the form of copper chloride. Initial tests using a typical silicon source showed that the reactor could be used to follow the consumption of Si with reproducibility of ±2%, and similar reproducibility was observed for product selectivity. The reactivity of a pure silicon and an industrial silicon sample were compared using the reactor and both samples showed identical reactivity and selectivity with respect to the amount of silicon consumed. Addition of Al metal (Cu:Al mole ratio=1.50, 0.30, 0.15) was found to significantly enhance reactivity and, to a much lesser extent, enhanced selectivity to dichlorodimethylsilane. Addition of CaCl2 (Cu:Ca mole ratio=0.530, 0.105, 0.053) significantly decreased reactivity but had no marked effect on selectivity. Modification of the CuCl catalyst is reported in which CuCl is reacted with silanes and a form of CuCl was synthesised with significantly increased reactivity but with high selectivity to light products.