(730f) Irreducible Co2SiO4 As a Promoter to Modify Co-Based Catalysts on Ordered Mesoporous Silica for Fischer-Tropsch Synthesis

It is commonly accepted that the formation of irreducible Co₂SiO₄ could lead to lower reducibility and lose of active sites on Co/SiO₂ catalyst. A philosophy originated from Traditional Chinese Medicine therapy of “combating poison with poison” provides a new strategy for designing more active Fischer-Tropsch synthesis (FTS) catalyst. Here, an innovative environment friendly method is developed to prepare ordered mesoporous silica (OMS), and the corresponding Co/OMS catalyst is more active than that of Co/SBA-15 with similar product selectivity. The mechanism of Co₂SiO₄ formation on Co/OMS and its promotion effect on FTS performance have been investigated in detail. For the Co/OMS catalyst, the formation of Co₂SiO₄ is verified occurring during the reduction process of Co/OMS. The Co₂SiO₄ is pre-incorporated as a modificant into the OMS support to form OMSCx support with Si/Co at different ratios of x. The results indicate that the pre-incorporated Co₂SiO₄ can make the active sites highly dispersed and prevent the interaction between supported Co⁰ and silica to further form Co₂SiO₄, which results in an enhanced FTS performance. In addition, the selectivity to CH₄ and C₂-C₄ undergoes an inverted cone change with the decrease of Si/Co ratio, while a 8.8% increase in C₅₊ selectivity is found on the modified Co/OMSC40 catalyst compared with Co/OMS on similar CO conversion. And a higher local CO/H₂ adsorption ratio on surface of Co/OMSC40 is demonstrated to facilitate carbon chain growth in FTS process. The incorporated Co₂SiO₄ in Co/OMSC40 reinforced metal-support interaction, anchored Co⁰ active sites high dispersely and avoided the agglomeration of Co⁰. Owing to the inhibited Co₂SiO₄ formation and improved Co⁰ dispersion, the Co/OMSC40 exhibited a better FTS stability.