Abstract: A diorganodichlorosilane is prepared by subjecting organochlorosilanes to disproportionation reaction in the co-presence of a SiH group-containing compound and in the presence of a primary catalyst of AlCl3 or AlBr3 and a co-catalyst of Mg, Al, Ca, Ti, Fe, Ni, Cu, Zn or Sn or a compound thereof. The invention enables disproportionation reaction of organochlorosilanes under atmospheric pressure and at a low temperature at which no substantial sublimation of AlCl3 or the like occurs, thus allowing the reaction equipment to be simple and improving the safety of reaction.

Abstract: A diorganodichlorosilane is prepared by subjecting organochlorosilanes to disproportionation reaction in the co-presence of a SiH group-containing compound and in the presence of a primary catalyst of AlCl3 or AlBr3 and a co-catalyst of Mg, Al, Ca, Ti, Fe, Ni, Cu, Zn or Sn or a compound thereof. The invention enables disproportionation reaction of organochlorosilanes under atmospheric pressure and at a low temperature at which no substantial sublimation of AlCl3 or the like occurs, thus allowing the reaction equipment to be simple and improving the safety of reaction.

Abstract: The direct synthesis of methylchlorosilanes to react metallic silicon with methyl chloride in the presence of a copper catalyst yields a high-boiling fraction of methylchlorodisilanes as by-products. The invention provides a method for preparing monosilanes from the high-boiling fraction by reacting it with hydrogen chloride in the presence of an amine or amide catalyst. The reaction is effected under the condition that the amount of iron, aluminum, zinc, tin and compounds thereof present in the reaction system is less than the equimolar amount with respect to the catalyst. This increases the conversion of disilanes into monosilanes.

Abstract: A process for producing a branched organopolysiloxane, comprising the steps of subjecting mixture of (A) a trialkoxysilane having the general formula (1):R.sup.1 Si(OR.sup.2).sub.3 (1)wherein R.sup.1 is a hydrocarbon group, and R.sup.2 are each a hydrocarbon group, and (B) an organosiloxane oligomer obtained by hydrolysis-condensation of a silane compound having the general formula (2):R.sup.3.sub.a SiCl.sub.4-a (2)wherein R.sup.3 are each a hydrocarbon group and a is 2 or 3, to equilibration reaction in the presence of an alkali catalyst, and adding water, subsequently to or concurrently with the equilibration reaction, to the reaction mixture, thereby hydrolyzing the Si--OR.sup.2 groups contained in the organopolysiloxane resulting from the hydrolysis-condensation. A branched organopolysiloxane stable in molecular composition and properties such as viscosity, can be produced.

Abstract: Siloxanes are purified by contacting siloxanes containing ionic crystals as an impurity with a polar solvent, evaporating the solvent, thereby increasing the mean particle size of the ion crystals, and removing the ion crystals from the siloxanes by filtration. The method enables brief, efficient purification of siloxanes in high yields, offering siloxanes having a minimal content of ionic crystals.

Abstract: A process for preparing a high molecular weight organopolysiloxane comprising: a first polymerization step of bringing a low molecular weight organopolysiloxane into reaction in the presence of a quaternary phosphonium hydroxide compound and/or a silanolate thereof as a catalyst under heating; and a second polymerization step for bringing the resulting reaction mixture into reaction in the presence of an alkali metal hydroxide and/or a silanolate thereof as a catalyst under heating. According to the process, a high molecular weight organopolysiloxane can be prepared using a reduced amount of catalyst for polymerization reaction, so that the amount of salts formed from a neutralizing agent is smaller and the subsequent filtration step for purification is less burdensome and easier to carry out.