Osmium as a potential Fischer-Tropsch catalyst using hollow carbon spheres as support

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%).