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

The effect of Al and Ca addition on formation of silanes in the Rochow Dire ct Process is described and discussed. The catalysts are evaluated in a sti rred-bed microreactor using on-line gas chromatographic analysis. The forma tion 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 sil icon source showed that the reactor could be used to follow the consumption of Si with reproducibility of +/-2%, and similar reproducibility was obser ved for product selectivity. The reactivity of a pure silicon and an indust rial 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:AI mole ratio=1.50, 0.30, 0.15) was fou nd to significantly enhance reactivity and, to a much lesser extent, enhanc ed selectivity to dichlorodimethylsilane. Addition of CaCl2 (Cu:Ca mole rat io=0.530, 0.105, 0.053) significantly decreased reactivity but had no marke d effect on selectivity. Modification of the CuCl catalyst is reported in w hich CuCl is reacted with silanes and a form of CuCl was synthesised with s ignificantly increased reactivity but with high selectivity to light produc ts. (C) 2001 Elsevier Science B.V. All rights reserved.