Cobalt-Fischer-Tropsch catalyst regeneration: the crucial role of the Kirkendall effect for cobalt redispersion

Redispersion of cobalt is a key process during Fischer–Tropsch catalyst regeneration. Using model catalysts we show that redispersion is a two step process. Oxidation of supported metallic cobalt nanoparticles produces hollow oxide particles by the Kirkendall effect; reduction leads to break-up of these hollow oxide shells, forming multiple metallic particles. This mechanism is to a large extent independent of the support.