Effect of the zirconia addition manner on the modification of Fe–SiO2 interaction

A series of ZrO2-modified Fe/SiO2 catalysts with the same composition were prepared by different methods. These solids were characterized by N2 adsorption, Fourier transform infrared spectroscopy, temperature-programmed reduction, temperature-programmed desorption, transmission electronic microscopy and Mössbauer spectroscopy. The results indicated that the modification of Fe–SiO2 interaction was strongly depended on the method of preparation. It was found that the strong Fe–SiO2 interaction could be effectively weakened if Zr species and SiO2 were pre-precipitated (Zr2-B and Zr2-C catalysts), even though the ZrO2 level was low. Consequently, the reduction and carburization ability of the catalyst was enhanced and the Fischer–Tropsch synthesis activity was increased eventually. The products selectivity variation trend indicated that the selectivity to gaseous and light hydrocarbons was increased, whereas that to heavy hydrocarbons and olefin was suppressed when the Zr species and SiO2 were precipitated before the precipitation of Fe3+ cation.