Abstract: A low molecular weight branched siloxane, typically methyltris(trimethylsiloxy)silane is effectively prepared in high yields by reacting a trichlorosilane, typically methyltrichlorosilane with a disiloxane, typically hexamethyldisiloxane in the presence of a linear phosphonitrilic chloride (LPNC) catalyst.

Abstract: A low molecular weight branched siloxane, typically methyltris(trimethylsiloxy)silane is effectively prepared in high yields by reacting a trichlorosilane, typically methyltrichlorosilane with a disiloxane, typically hexamethyldisiloxane in the presence of a linear phosphonitrilic chloride (LPNC) catalyst.

Abstract: Alkylhalosilanes are produced by first fluidizing a metallic silicon powder with an inert gas, preheating the silicon powder at a temperature between 200.degree. C. and a steady reaction temperature while keeping the silicon powder fluidized, adding a copper catalyst to the preheated silicon powder to form a contact mass, and feeding an alkyl halide into the contact mass whereby the alkylhalosilanes are formed by direct synthesis. This process prevents the copper catalyst from being sintered by thermal hysteresis and activates a high catalysis on the contact mass at the start of reaction. The desired dialkyldihalosilane can be produced at a high selectivity.

Abstract: An alkylhalosilane is prepared by charging a reactor with a contact mass comprising a metallic silicon powder and a copper catalyst, and feeding an alkyl halide into the reactor whereby the silane is formed by direct synthesis. The contact mass contains 1-10,000 ppm of elemental boron. The addition of boron to the contact mass is effective for increasing the throughput of dialkyldihalosilane at desired STY in an inexpensive manner while suppressing formation of unnecessary hydrosilanes and disilanes.

Abstract: An alkylhalosilane is prepared by charging a reactor with a contact mass comprising a metallic silicon powder and a copper catalyst, and feeding an alkyl halide into the reactor whereby the silane is formed by direct synthesis. The use of a metallic silicon powder having a specific particle size distribution ensures effective fluidization whereby the alkylhalosilane of quality is formed at a high selectivity and in high yields.

Abstract: An alkylhalosilane is prepared by charging a reactor with a contact mass comprising metallic silicon powder and a copper catalyst and feeding a reactant gas containing an alkyl halide into the reactor whereby the silane is formed by direct synthesis. A phosphorus compound is added to the contact mass in an amount of 3,000-10,000 ppm calculated as phosphorus. The invention produces a more amount of dialkyldihalosilane in a desirable STY while minimizing the amount of unnecessary disilanes.