EFFECTS OF HYDROGEN-CHLORIDE ADDITION TO THE DIRECT REACTION OF METHYLENE-CHLORIDE WITH ELEMENTAL SILICON

Direct synthesis of bis(chlorosilyl)methanes has been reinvestigated b y reacting elemental silicon simultaneously with methylene chloride an d hydrogen chloride in the presence of copper catalyst using a stirred reactor equipped with a spiral band agitator at a carefully controlle d temperature between 260 and 340 degrees C. Bis(dichlorosilyl)methane and (dichlorosilyl)(trichlorosilyl)methane were obtained as the major products and bis(trichlorosilyl)methane as a minor product along with trichlorosilane and tetrachlorosilane derived from the reaction betwe en elemental silicon and hydrogen chloride. The decomposition of methy lene chloride was suppressed and the production of polymeric carbosila nes reduced by adding hydrogen chloride to the methylene chloride reac tant, The optimum mixing ratio of methylene chloride and hydrogen chlo ride for the direct synthesis of bis(silyl)methanes was 1:4. The deact ivation problem of elemental silicon owing to decompositions of methyl ene chloride and polycarbosilanes was eliminated. Cadmium was a good p romoter for the reaction, while zinc was found to be an inhibitor for this particular reaction.