The separation method separates a polyalcohol compound from water, so as to obtain a purified product stream comprising the polyalcohol compound in output concentration of at least 90 wt %. Thereto, a mixture of the polyalcohol compound and water is provided, said mixture having a polyalcohol concentration. The polyalcohol concentration of mixture is increased in an evaporation stage, at least a portion of which is operated in at first pressure. Subsequently, the mixture is treated in distillation stage to be deliver the stream comprising the polyalcohol compound in the output concentration of at least 90 wt %, which distillation stage is operated at a second pressure. Herein, the distillation stage is operated to produce steam output, that optionally compressed to a third pressure and is coupled to the evaporation stage. The second pressure and/or any third pressure is higher than first pressure. The reactor system is configured for performing the separation method.