Effect of high-temperature pre-reduction in Fischer–Tropsch synthesis on Fe/ZrO2 catalysts

• Fe-loaded ZrO2 catalysts were tested in CO hydrogenation.
• Pre-reduction at high temperature (900–930 °C) develops formation of intermetallic Fe2Zr and FeZr2.
• ZrO2 favors iron dispersion.
• Catalysts containing intermetallic Fe2Zr and FeZr2 phases are much more active in CO hydrogenation than those containing only Fe.

Fischer–Tropsch synthesis of low molecular weight (C2C4) olefins is a valuable alternative process for the production of key chemicals from non-petroleum precursors such as a renewable C source like biomass. The influence of the H2 treatment temperature of zirconia-supported iron catalysts on the conversion of synthesis gas has been investigated. The CO conversion rate, based on steady-state, increased with the pretreatment temperature up to a maximum and then decreased at higher temperatures. Moreover, methane selectivity was found to decrease slightly from the lowest H2 treatment temperatures (46%) to the highest ones (34%), while C2C4 and C5+ hydrocarbons followed an opposite trend. Presumably, methane formation takes place at highly active low coordination sites residing at corners and edges, which are more abundant on small iron carbide particles. Lower hydrocarbons are mainly produced at terrace sites that are available and active, quite independent of the iron crystallite size.

Catalysts in which Zr2Fe and ZrFe2 phases have been developed are much more active than that containing only Fe phases.Figure optionsDownload high-quality image (99 K)Download as PowerPoint slide