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.
