Method for separating an exhaust-gas mixture containing hydrogen chloride, hydrogen and chlorosilanes

Process for separating an offgas mixture, comprising:

• providing an offgas mixture comprising hydrogen chloride, hydrogen and chlorosilanes;
• step a) contacting the offgas mixture with an absorbent in an absorption column at a temperature of −70 to −10° C. and a pressure of 0.5 to 2 MPa, where the hydrogen chloride and the chlorosilanes are absorbed with formation of a laden absorbent, and a hydrogen-containing first gas phase is discharged;
• step b) desorbing a gas stream from the laden absorbent in a desorption column at a temperature of 50 to 150° C. and/or a pressure, reduced relative to the step a), of 0.1 to 1 MPa;
• wherein after the step a) and before the step b), the laden absorbent is depressurized in at least one outgassing unit at a temperature increased relative to the step a) and/or at a pressure reduced relative to the step a) at a top end of the outgassing unit and, by removal of a resultant second gas phase, hydrogen is removed from the laden absorbent, where the desorbed gas stream in the step b) has a hydrogen fraction of ≤10 mol %, a hydrogen chloride fraction of ≥89 mol % and a chlorosilane fraction of ≤1 mol %, where the mean hydrodynamic residence time of the laden absorbent in the outgassing unit is 1 to 40 s.