Revealing the activity of different iron carbides for Fischer-Tropsch synthesis

Exploring the structure of iron-based catalysts on the catalytic performance of Fischer-Tropsch synthesis (FTS) reaction has attracted much attention. With this in mind, the mixture of SiO2 or Al2O3 powder and non-porous iron oxide powder (alpha-Fe2O3) have been investigated for understanding the nature role of different iron carbides in the FTS reaction by adjusting the formation of iron carbides. Under the typical FTS reaction conditions, the CO conversion of Al2O3/alpha-Fe2O3 = 1 catalyst could reach up to 61.6 %, which is about 3.3 times that of the pure alpha-Fe2O3 catalyst. Based on the characterization results, including in situ XPS and CO-DRIFTS as well as Mossbauer spectra, it is found that the electronic state of iron atoms is affected by the existence of SiO2 or Al2O3, and the interactions of Fe-Si or Fe-Al are formed on the surface of iron powder, which plays an important role in formation of C-rich iron carbide active phase (epsilon-Fe2C). Although chi-Fe5C2 is usually as the active phase in the FTS reaction, we have found that the content of epsilon-Fe2C is more positive to activity.

Automated summary

Research on iron-based catalysts doped with SiO2 or Al2O3 has shown that adjusting the formation of iron carbides can enhance the activity of Fischer-Tropsch synthesis reactions. Characterization results using techniques such as XPS and CO-DRIFTS revealed that SiO2 or Al2O3 affects the electronic state of iron atoms and promotes the formation of Fe-Si or Fe-Al interactions on the surface of iron powder, which in turn plays a key role in the formation of the active phase ε-Fe2C. The content of ε-Fe2C is found to be more beneficial to activity compared to the traditionally recognized active phase χ-Fe5C2 in Fischer-Tropsch synthesis reactions.