Embodiments of the invention relate to a method for operating a steam cycle process performed in an apparatus having an evaporator or steam generator for the evaporation of a liquid working medium and an expander, which is lubricated by a lubricant, for the performance of mechanical work. The method comprises a) supplying the liquid working medium to the evaporator, in which it evaporates and is fed to the expander in the form of steam; b) supplying an ionic liquid, which at room temperature forms two liquid phases with the liquid working medium, to the expander as a lubricant; and c) separating the ionic liquid forming the lubricant for the expander from the working medium upstream of the evaporator.