Titania-Decorated Silicon Carbide-Containing Cobalt Catalyst for Fischer-Tropsch Synthesis

摘要

The metal-support interactions of titanium dioxide decorated silicon carbide (β-SiC)-supported cobalt catalyst for Fischer-Tropsch synthesis (FTS) were explored by a combination of energy-filtered transmission electron microscopy (EFTEM), 59Co zero-field nuclear magnetic resonance (59Co NMR), and other conventional characterization techniques. From the 2D elemental maps deduced by 2D EFTEM and 59Co NMR analyses, it can be concluded that the nanoscale introduction of the TiO2 into the β-SiC matrix significantly enhances the formation of small and mediumsized cobalt particles. The results revealed that the proper metal-support interaction between cobalt nanoparticles and TiO2 led to the formation of smaller cobalt particles (<15 nm), which possess a large fraction of surface atoms and, thus, significantly contribute to the great enhancement of conversion and the reaction rate. The cobalt time yield of the catalyst after modification increased to 7.5 × 10~(-5) molCO gCo~(-1) s~(-1) at 230 °C, whereas the C~(5+) selectivity maintained a high level (>90%). In addition, the adequate meso- and macro-pores of the SiC-based support facilitated intimate contact between the reactants and active sites and also accelerated the evacuation of the intermediate products. It was also worth noting that a superior and stable FTS specific rate of 0.56 gC~(5+) gcatalyst~(-1) h~(-1) together with high C~(5+) selectivity of 91% were obtained at common industrial content of 30 wt % cobalt.