Abstract: The invention provides a process for hydrogenating silicon tetrachloride in a reactor, in which reactant gas containing hydrogen and silicon tetrachloride is heated to a temperature of greater than 900° C. at a pressure between 4 and 15 bar, first by means of at least one heat exchanger made from graphite and then by means of at least one heating element made from SiC-coated graphite, the temperature of the heating elements being between 1150° C. and 1250° C., wherein the reactant gas includes at least one boron compound selected from the group consisting of diborane, higher boranes, boron-halogen compounds and boron-silyl compounds, the sum of the concentrations of all boron compounds being greater than 1 ppmv based on the reactant gas stream.