Fe-containing carbon obtained from ferrocene: Influence of the preparation procedure on the catalytic performance in FTS reaction

Abstract

Four different preparation routes were applied to obtain Fe-containing carbon catalysts for Fischer Tropsch Synthesis (FTS) including copolymer assisted co-precipitation of iron precursor, chemical modification of ferrocene, sol-gel and wetness impregnation of iron on polymeric carbon. The effects of the FTS reaction temperature and pressure were also examined. Using ferrocene as a starting precursor and applying sol-gel method to prepare the solid, the syngas is readily converted to C10+ hydrocarbons with a conversion of up to 56% and a productivity of 34mg hydrocarbon.gcat−1.h−1 at 240°C and 20atm. Impregnation method gave a Fe/C based catalyst with the highest exposure of active sites, including surface Fe3+ and Fe2+ redox sites with great properties in FTS. Chemical modification of ferrocene route enables the formation of hematite and maghemite nanoparticles on carbon, which were in situ reduced to magnetite and iron carbides, being the latter mostly active for the water gas shift reaction. It is found that copolymer assisted co-precipitation of ferrocene facilitates the production of large crystals of magnetite, which suffered from sintering and coking exhibiting low performance in FTS. Among these methods, sol-gel based catalyst proved to have superior performance due to the good dispersion of Fe, stable magnetite and iron carbide and Fe-doped nitrogen carbon phases production. Based on spent catalysts characterizations, the synergetic effect between magnetite and the iron carbides phases in the sol-gel based catalyst plays an important role in heavy hydrocarbon formation.