MOFs-assisted synthesis of robust and efficient cobalt-based Fischer–Tropsch catalysts

Abstract

The supported catalyst featuring highly dispersed active species is a challenge for industrial catalyst even with high loadings. The traditional impregnation method generally results in large particles due to the particle migration and coalescence or Ostwald ripening process. Herein, a Metal-Organic Frameworks (MOFs) strategy was proposed to assist the manufacture of supported CoOx/SiO2 catalyst. The classic organic ligand (e.g., 2-methylimidazoles) was coordinated with cobalt ions dispersed in advance on silica support, which was post-treated as a sacrificial and protective agent in different atmosphere. These operations can effectively restrain the growth of cobalt particles, yielding the high dispersion of Co metal active sites. The prepared catalyst (CoOx/SiO2-A#) exhibits superior activity, C5+ selectivity and stability in Fischer–Tropsch synthesis. It reveals that the high dispersion as well as the increased number of surface-exposed Co sites contribute to superior activity. As demonstrated by TG-MS and Raman characterizations, a large amounts of carbon species in CoOx/SiO2-N catalyst impeded the accessible active sites. The existence of Co2SiO4 verified by TPR and XPS characterizations means the strong metal-support interaction, that contributes robust performance in long-term stability test. This sacrificial MOFs strategy paves the way for the design of highly dispersed and robust FTS catalysts.