Recent developments in catalyst pretreatment technologies for cobalt based Fisher-Tropsch synthesis

Stringent environmental regulations and energy insecurity necessitate the development of an integrated process to produce high-quality fuels from renewable resources and to reduce dependency on fossil fuels, in this case Fischer-Tropsch synthesis (FTS). The FT activity and selectivity are significantly influenced by the pretreatment of the catalyst. This article reviews traditional and developing processes for pretreatment of cobalt catalysts with reference to their application in FTS. The activation atmosphere, drying, calcination, reduction conditions and type of support are critical factors that govern the reducibility, dispersion and crystallite size of the active phase. Compared to traditional high temperature H2 activation, both hydrogenation-carbidisation-hydrogenation and reduction-oxidation-reduction pretreatment cycles result in improved metal dispersion and exhibit much higher FTS activity. Cobalt carbide (Co2C) formed by CO treatment has the potential to provide a simpler and more effective way of producing lower olefins, and higher alcohols directly from syngas. Syngas activation or direct synthesis of the metallic cobalt catalyst has the potential to remove the expensive H2 pretreatment procedure, and consequently simplify the pretreatment process, which would make it more economical and thus more attractive to industry.