Selectivity loss in Fischer-Tropsch synthesis : The effect of cobalt carbide formation

International audience; Fischer-Tropsch cobalt catalyst deselectivation was studied using accelerated aging treatments dedicated to the carburization phenomenon. Cobalt carbide was successfully obtained by CO treatments, with limited simultaneously carbon deposition nor sintering. Particle sizes were found to influence the catalyst sensitivity to carburization, likely because of a possible core–shell mechanism. An important loss of both activity and selectivity to heavy products was observed after the treatments, making carburization one of the potential mechanisms responsible for deselectivation in Fischer-Tropsch synthesis. Side products were also impacted by cobalt carbide formation, with an increase of CO2 production and a decrease of the selectivity to olefins. The extent of carburization was found to directly dictate the level of the selectivity shift.