Abstract: A process is disclosed for unpressurized catalytic conversion of organic solids into oil, with the steps of conditioning the starting material, cracking in an oil reactor with simultaneous distilled separation of the desired hydrocarbon section, and discharging the solids obtained in the reaction, wherein conditioning of the floatable solid starting materials takes place in a micro vortex mill in an air carrier flow, and the resulting material particles are converted in the oil reactor, either directly or after temporary storage, with a dry content of ?90% and a grain size of ?100 ?m, in particular ?63 ?m. Conditioning according to the invention can be used for all types of floatable organic solids and their mixtures. After processing in the micro vortex mill, the products supplied to the oil reactor produce high product yields with shorter reaction times, thereby substantially improving the economic benefits of the process.