(178c) A Study of the Ageing and Deactivation Phenomena Occurring during Operation of an Iron Catalyst in Extended FTS Runs

Sintering, oxidation and carbon deposition during Fischer-Tropsch synthesis has long been postulated as some major deactivation mechanisms. Catalyst from three different reactors operated under similar conditions but initially reduced differently were discharged from the reactors after extended time on stream (TOS) ca.14800 hours. Low pressure FTS activity measurements reveal deactivation of the catalyst. Spent catalyst fractions from the reactors were characterized with various techniques including TGA, Fourier transform IR, XPS, Raman spectroscopy, X-ray diffraction (XRD), elemental analysis with ICP-OES, HRTEM. It was found that there was no noticeable crystalline growth or sintering during operation but accumulation of carbonaceous materials around the particles. It is concluded that the deactivation primarily was due to formation and deposition of carbonaceous specie amorphous carbon entrapped within the pores of the catalyst contributing 25.49± 0.56 % and graphitic carbon 14.56 ± 0.60%.