Modification of Fe–SiO2 interaction with zirconia for iron-based Fischer–Tropsch catalysts

The modification of Fe–SiO2 interaction in iron catalysts for Fischer–Tropsch synthesis (FTS) by the incorporation of ZrO2 was investigated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction, powder X-ray diffraction, transmission electronic microscopy, and Mössbauer spectroscopy. The results indicated that the strong Fe–SiO2 interaction could be explained in terms of the formation of Fe–O–Si bonds between iron and SiO2, and these bonds were effectively weakened by ZrO2, which consequently enhanced the reduction and carburization of the catalyst and improved the stability of the iron carbides formed. FTS performances, tested in a fixed-bed reactor, showed that both the activity and the image selectivity of the Zr-modified catalysts first increased, passed a maximum at Zr loading of 100Fe/20SiO2–20ZrO2 with increasing zirconia, and then decreased dramatically at higher Zr loadings. The acid content in the water phase decreased, while the alcohol content increased with the addition of zirconia.