The deactivation of cobalt catalyst on the carbon nanotubes (CNTs) as an inert support in Fischer-Tropsch synthesis (FTS) has been modeled assuming a sintering is the dominant mechanism. The mechanism that is correlating to the cobalt crystallite size growth has been used to describe the catalyst activity decline with time on stream. A thermodynamic size dependent kinetic equation is used to investigate the crystal growth during the deactivation process. Because of no interaction between support and active phase, sintering is the dominant mechanism in Co/CNTs catalyst. The FTS reaction rates for this sintering scenario were calculated using size dependent kinetic equation and compared with experimental results. The difference between experimental results and the calculated FTS rate results of sintering is related to other deactivation routes, which main is deactivation by coking.

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