Integrated process, in which pure carbonyl iron powder (CIP) is prepared by decomposition of pure iron pentacarbonyl (IPC) in a plant A, carbon monoxide (CO) liberated in the decomposition of the IPC is used in plant A for the preparation of further CIP from iron or is fed to an associated plant B for the preparation of synthesis gas or is fed to an associated plant C for the preparation of hydrocarbons from synthesis gas, and the CIP prepared in plant A is used as catalyst or catalyst component in an associated plant C for the preparation of hydrocarbons from synthesis gas from plant B.