The present invention relates to a process for producing normally gaseous, normally liquid and optionally normally solid hydrocarbons during a production cycle (i.e. between regenerations or between start-up with freshly loaded catalyst and the first regeneration) by catalytic conversion of synthesis gas in a multiple reactor arrangement comprising at least two parallel operating reactors containing a catalyst capable of converting synthesis gas to hydrocarbons, and each reactor having a different relative reaction rate, wherein synthesis gas is distributed to each reactor at a feed rate proportional to the relative reaction rate in the respective reactor. It further relates to a reactor arrangement suitable for operating the process according to the invention for producing normally gaseous, normally liquid and optionally normally solid hydrocarbons during a production cycle by catalytic conversion of synthesis gas comprising at least two parallel operating reactors, each containing a catalyst, wherein the reactors are connected to a common header for the distribution of synthesis gas to the reactors, and wherein the common header comprises a distribution means for selectively controlling the amount of synthesis gas fed to each reactor.