Fundamental understanding of deactivation and regeneration of cobalt Fischer–Tropsch synthesis catalysts

Cobalt Fischer–Tropsch Catalyst Regeneration: The Crucial Role of the Kirkendall Effect for Cobalt Redispersion

“…A fundamental understanding of the deactivation mechanisms at play during FTS is key to designing an efficient regeneration process. Most of the research on cobalt catalyst deactivation in the last 15 years has focused on oxidation as a deactivation mechanism [1]. Our previous work however, showed that oxidation is not a deactivation mechanism during FTS for supported Co catalysts with crystallite size in excess of 2 nm [1,[4][5][6].…”

“…Due to the cost of both cobalt and noble metals, which are often used as promoters, extended catalyst life, is required to make the process economically feasible. Apart from the synthesis of a relatively stable fresh catalyst regeneration can be used to extend the lifetime of Co FTS catalysts [1][2][3]. A fundamental understanding of the deactivation mechanisms at play during FTS is key to designing an efficient regeneration process.…”

“…On the contrary, the FT environment was found to be strongly reducing [4]. Following a comprehensive study into the deactivation of a cobalt catalyst under realistic FTS conditions the following intrinsic deactivation mechanisms were identified (1) sintering of Co active phase [1,7] (2) carbon deposition [1,8] and (3) possibly surface reconstruction [1,9,10]. Having identified these mechanisms a three step regeneration process, i.e.…”

Sintering Behavior of TiO2-Supported Model Cobalt Fischer–Tropsch Catalysts under H2 Reducing Conditions and Elevated Temperature

“…Deactivation mechanisms for cobalt-based catalysts include (i) poisoning by sulphur and nitrogen compounds, (ii) cobalt oxidation, (iii) cobalt-support compound formation, (iv) sintering of cobalt crystallites, (v) surface reconstruction and (vi) carbon deposition. Of all the deactivation mechanisms stated, sintering, carbon formation and surface reconstruction are said to be intrinsic to cobalt and therefore will be present in most cobalt catalyst systems 7,8 Sintering in this context can be defined as the change in dispersion of the active metal during use or during treatment at high temperatures. Sintering results in loss of catalytic surface area due to crystal growth or loss of support area due to collapse of support 9,10 .…”

Recent developments in the application of nanomaterials to understanding molecular level processes in cobalt catalysed Fischer–Tropsch synthesis

“…A further study of a mixture of a reduced Co metal and an oxidised CoO conventional catalyst that becomes more reduced under 20 bar / 230 ºC reaction conditions over time appears to conflict with the above results; however, as this catalyst is Pt promoted it may behave differently with respect to reduction of the cobalt (see below). 54 Overall the ability to prepare nanoparticles of well-defined sizes (e.g. samples with a particle size distribution of only  0.5 nm 46 ) by a selection of routes has confirmed a particle size effect exists.…”