Surface speciation of Co based Fischer-Tropsch catalyst under reaction conditions: Deactivation by coke or by oxidation?

Thermodynamic assessment of the stability of bulk and nanoparticulate cobalt and nickel during dry and steam reforming of methane

“…The oxidation behaviour of nano-sized Co 0 structures has been under discussion in the Fischer–Tropsch community for a long time. 15,16,23,24,54,85–89 Recent experimental studies employing sophisticated in situ characterisation techniques 16,54,87,88 together with insight from theoretical work 89 enabled a compelling understanding of the mechanisms at play during water induced oxidation. 25 The hypothesised size dependent oxidation behaviour of Co 0 to CoO, as predicted by van Steen et al , 15 has been confirmed for 220 °C.…”

“…The oxidation behaviour of nano-sized Co 0 structures has been under discussion in the Fischer-Tropsch community for a long time. 15,16,23,24,54,[85][86][87][88][89] Recent experimental studies employing sophisticated in situ characterisation techniques 16,54,87,88 together with insight from theoretical work 89 enabled a compelling understanding of the mechanisms at play during water induced oxidation. 25 The hypothesised size dependent oxidation behaviour of Co 0 to CoO, as predicted by van Steen et al, 15 has been conrmed for 220 C. 16,25,54,87,88 However, oxidation was demonstrated to rather occur due to a hindered removal of adsorbed oxygen species from the surface upon CO dissociation at high partial pressures of H 2 O rather than direct oxidation of Co 0 by water splitting.…”

“…25 The hypothesised size dependent oxidation behaviour of Co 0 to CoO, as predicted by van Steen et al, 15 has been conrmed for 220 C. 16,25,54,87,88 However, oxidation was demonstrated to rather occur due to a hindered removal of adsorbed oxygen species from the surface upon CO dissociation at high partial pressures of H 2 O rather than direct oxidation of Co 0 by water splitting. 88,89 The latter reaction was consequentially hypothesized to be kinetically hindered at 220 C, 16,17,25,88 which is likely to change at elevated operation temperatures during reforming of methane. The elevated temperatures may also allow for oxidation of Co 0 by CO 2 , which was demonstrated to be kinetically hindered in 90% CO 2 /Ar at temperatures below 150 C. 78 Aside from thermodynamically favoured oxidation, nanosized material is also expected to display a lower thermal resistance against sintering when compared to bulk structures.…”

Effects of Site Geometry and Local Composition on Hydrogenation of Surface Carbon to Methane on Ni, Co, and NiCo Catalysts

“…More importantly, Co shows a higher resistance to carbon poisoning. However, it forms carbon deposits (sheets and filaments) in other reactions, such as ethanol dehydrogenation [3], and has been found to deactivate by oxidation at high temperatures used in DRM processes [4,5]. Co forms homogeneous alloys with nickel over wide composition and temperature ranges [6], making it a good candidate for a bimetallic CoNi catalyst.…”

Achievements and Expectations in the Field of Computational Heterogeneous Catalysis in an Innovation Context

“…The deactivation of metallic catalysts may also be investigated by first principles approaches. [42] These questions are even more complex when dealing with metallic alloys, as the respective locations of the metals need to be addressed. [35,[43][44][45][46][47][48][49] The segregation of one metal with respect to the other is an important question, which is also affected by environmental parameters, such as adsorption of the reactants.…”