Process for converting silicon tetrachloride to trichlorosilane

The invention relates to a process for converting silicon tetrachloride (STC) to trichlorosilane (TCS), by introducing reactant gas containing STC and hydrogen into a reaction zone of a reactor in which the temperature is 1000-1600° C., wherein the reaction zone is heated by a heater located outside the reaction zone and the product gas containing TCS which forms is then cooled, with the proviso that it is cooled to a temperature of 700-900° C. within 0.1-35 ms, wherein the reactant gas is heated by the product gas by means of a heat exchanger working in countercurrent, wherein reactor and heat exchanger form a single, gas-tight component, wherein the component includes one or more ceramic materials selected from the group consisting of silicon carbide, silicon nitride, graphite, SiC-coated graphite and quartz glass.