Deactivation of cobalt based Fischer–Tropsch catalysts: A review

To trace the origin of catalyst deactivation is in many cases difficult. It is usually a complex problem where several mechanisms contribute to the loss of activity/selectivity. Low temperature Fischer–Tropsch synthesis (FTS) is a three phase system having a wide range of products and intermediates. Additionally, high partial pressures of steam will arise during reaction. Thus, the chemical environment in the Fischer–Tropsch synthesis reactor encompasses a large number of interacting species which may negatively affect catalytic activity. Furthermore, it is an exothermic reaction and local overheating might occur. Utilization of the produced heat is crucial and the choice of the reactor should be done with respect to the catalyst stability properties. Catalyst deactivation in the Fischer–Tropsch reaction has been a topic of industrial as well as academic interest for many years. The main causes of catalyst deactivation in cobalt based FTS as they appear in the literature are poisoning, re-oxidation of cobalt active sites, formation of surface carbon species, carbidization, surface reconstruction, sintering of cobalt crystallites, metal–support solid state reactions and attrition.