Osmium as a potential Fischer-Tropsch catalyst using hollow carbon spheres as support
Date
2018
Authors
Tshepo, Molefe
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Abstract
Little attention has been given to the use of osmium as a catalyst or promoter for Fischer
Tropsch synthesis (FTS). In this study the synthesis and use of osmium nanoparticles supported
or encapsulated inside hollow carbon sphere (HCS) as a potential FT catalyst is reported. Os is
not expected to be a good FT catalyst and this study provided for an evaluation of the role of
Os on carbon as a catalyst in the FT reaction. The Os was encapsulated inside hollow carbon
spheres (HCSs) as this will eventually allow for a study of spillover effects in FT reactions.
The Os@HCS was prepared using sacrificial Stӧber silica spheres as a template. The SiO2
spheres were loaded with Os ((NH4)2OsCl6 metal precursor) via two methods: homogenous
deposition precipitation (HDP) and wetness impregnation (WI). The Os/SiO2 was encapsulated
by a carbon layer deposited by CVD using toluene. Removal of the sacrificial template gave
Os@HCS (dOs = 11-17.5 nm; dHCS = 450-560 nm). Numerous physicochemical properties were
used to reveal that the Os@HCS catalyst had been successfully synthesized. These included
electron microscopy, PXRD, TGA, BET, and TPR studies. In the FTS evaluation, the
Os@HCS and Os/SiO2 (as reference) showed low activity compared to conventional FT
catalysts. The Os supported catalysts showed a product selectivity mainly to C1 and C2
hydrocarbons with high selectivity towards methane (> ~65%).
Description
A dissertation submitted to the Faculty of Science, University of the Witwatersrand,
Johannesburg, in fulfillment of the requirements for the Degree of Masters of Science in
Chemistry
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Citation
Molefe, Tshepo (2018) Osmium as a potential Fischer-Tropsch catalyst using hollow carbon spheres as support,University of the Witwatersrand, Johannesburg, <http://hdl.handle.net/10539/25876>