Water-Induced Formation of Cobalt-Support Compounds under Simulated High Conversion Fischer–Tropsch Environment

ACS Catalysis ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 4902-4918 ◽  
Author(s):  
Moritz Wolf ◽  
Emma K. Gibson ◽  
Ezra J. Olivier ◽  
Jan H. Neethling ◽  
C. Richard A. Catlow ◽  
...  
Keyword(s):  
High Conversion ◽  
Fischer Tropsch

Size dependent stability of cobalt nanoparticles on silica under high conversion Fischer–Tropsch environment

2017 ◽  
Vol 197 ◽  
pp. 243-268 ◽  
Author(s):  
Moritz Wolf ◽  
Hendrik Kotzé ◽  
Nico Fischer ◽  
Michael Claeys
Keyword(s):  
Type Species ◽  
Tropsch Synthesis ◽  
High Conversion ◽  
Metallic Surface ◽  
Metallic State ◽  
Direct Oxidation ◽  
Fischer Tropsch ◽  
Fischer Tropsch Synthesis ◽  
Metal Support ◽  
Presence And Absence

Highly monodisperse cobalt crystallites, supported on Stöber silica spheres, as model catalysts for the Fischer–Tropsch synthesis were exposed to simulated high conversion environments in the presence and absence of CO utilising an in house developedin situmagnetometer. The catalyst comprising the smallest crystallites in the metallic state (average diameter of 3.2 nm) experienced pronounced oxidation whilst the ratio of H2O to H2was increased stepwise to simulate CO conversions from 26% up to complete conversion. Direct exposure of this freshly reduced catalyst to a high conversion Fischer–Tropsch environment resulted in almost spontaneous oxidation of 40% of the metallic cobalt. In contrast, a model catalyst with cobalt crystallites of 5.3 nm only oxidised to a small extent even when exposed to a simulated conversion of over 99%. The largest cobalt crystallites were rather stable and only experienced measurable oxidation when subjected to H2O in the absence of H2. This size dependency of the stability is in qualitative accordance with reported thermodynamic calculations. However, the cobalt crystallites showed an unexpected low susceptibility to oxidation,i.e.only relatively high ratios of H2O to H2partial pressure caused oxidation. Similar experiments in the presence of CO revealed the significance of the actual Fischer–Tropsch synthesis on the metallic surface as the dissociation of CO, an elementary step in the Fischer–Tropsch mechanism, was shown to be a prerequisite for oxidation. Direct oxidation of cobalt to CoO by H2O seems to be kinetically hindered. Thus, H2O may only be capable of indirect oxidation,i.e.high concentrations prevent the removal of adsorbed oxygen species on the cobalt surface leading to oxidation. However, a spontaneous direct oxidation of cobalt at the interface between the support and the crystallites by H2O forming presumably cobalt silicate type species was observed in the presence and absence of CO. The formation of these metal–support compounds is in accordance with conducted thermodynamic predictions. None of the extreme Fischer–Tropsch conditions initiated hydrothermal sintering. Seemingly, the formation of metal–support compounds stabilised the metallic crystallites and/or higher partial pressures of CO are required to increase the concentration of mobile, cobalt oxide-type species on the metallic surface.

Role of CO in the Water-Induced Formation of Cobalt Oxide in a High Conversion Fischer–Tropsch Environment

ACS Catalysis ◽  
2018 ◽  
Vol 8 (5) ◽  
pp. 3985-3989 ◽  
Author(s):  
Moritz Wolf ◽  
Bridget K. Mutuma ◽  
Neil J. Coville ◽  
Nico Fischer ◽  
Michael Claeys
Keyword(s):  
Cobalt Oxide ◽  
High Conversion ◽  
Fischer Tropsch

scholarly journals Performance of diffusion-optimised Fischer–Tropsch catalyst layers in microchannel reactors at integral operation

2019 ◽  
Vol 9 (9) ◽  
pp. 2180-2195 ◽  
Author(s):  
Henning Becker ◽  
Robert Güttel ◽  
Thomas Turek
Keyword(s):  
Simulation Study ◽  
High Conversion ◽  
Fischer Tropsch ◽  
Microchannel Reactors ◽  
Catalyst Layers

Simulation study evaluating impact of diffusion on selectivity and productivity for optimised catalyst layers operated at high conversion.

Decoupling the deactivation mechanisms of a cobalt Fischer–Tropsch catalyst operated at high conversion and ‘simulated’ high conversion

2020 ◽  
Vol 10 (20) ◽  
pp. 7056-7066 ◽  
Author(s):  
Chelsea Lyn Tucker ◽  
Michael Claeys ◽  
Eric van Steen
Keyword(s):  
High Conversion ◽  
Fischer Tropsch

In situ magnetometer study shows that high conversions facilitate sintering, reversible Co(ii)O and irreversible CoAl2O4 formation within cobalt-based Fischer–Tropsch systems.

Feasible Ways to Achieve High Conversion in Thorium-Fueled CANDU and PWR Reactors

2009 ◽  
pp. 62-72 ◽  
Author(s):  
P. Guillemin ◽  
A. Nuttin ◽  
A. Bidaud ◽  
J. Brizi ◽  
N. Capellan ◽  
...  
Keyword(s):  
High Conversion

Fischer-Tropsch waxes VII. The thermal conductivity of hard wax

1974 ◽  
Vol 24 (1-2) ◽  
pp. 81-91 ◽  
Author(s):  
Johannes H. Le Roux ◽  
Roy D. F. Smith ◽  
Richard Turner ◽  
Onno Weidema
Keyword(s):  
Thermal Conductivity ◽  
Fischer Tropsch
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