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 medium-sized 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 C5+ 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 gC5+ gcatalyst –1 h–1 together with high C5+ selectivity of 91% were obtained at common industrial content of 30 wt % cobalt.
The Fischer-Tropsch (FT) process, in which synthesis gas (syngas) derived from coal, natural gas, and biomass is converted into synthetic liquid fuels and chemicals, is a strongly exothermic reaction, and thus, a large amount of heat is generated during the reaction that could severely modify the overall selectivity of the process. In this Review, we report the advantages that can be offered by different thermally conductive supports, that is, carbon nanomaterials and silicon carbide, pure or doped with different promoters, for the development of more active and selective FT catalysts. This Review follows a discussion regarding the clear trend in the advantages and drawbacks of these systems in terms of energy efficiency and catalytic performance for this most-demanded catalytic process. It is demonstrated that the use of a support with an appropriate pore size and thermal conductivity is an effective strategy to tune and improve the activity of the catalyst and to improve product selectivity in the FT process. The active phase and the recovery of the support, which also represents a main concern in terms of the large amount of FT catalyst used and the cost of the active cobalt phase, is also discussed within the framework of this Review. It is expected that a thermally conductive support such as β-SiC will not only improve the development of the FT process, but that it will also be part of a new support for different catalytic processes for which high catalytic performance and selectivity are strongly needed.
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