An alternative process and device for carrying out Fischer Tropsch (FT) syntheses is proposed, allowing the reactant entities that take part in the FT reaction to be activated and their contributions, whether by quantity or by proportion, to be adjusted. The process consists in making a particulate phase, optionally consisting of catalytic particles, flow through a reactor. While flowing through the reactor, the particulate phase is subjected at regular intervals to the action of a plasma obtained from a gas, such as hydrogen, thus enabling hydrogen activation for hydrogenation of carbon monoxide, or carbon monoxide activation in order to lengthen the carbon chains.