Abstract
For the rWGS reaction, Fe5C2 (Hagg’s carbide) catalyst exhibits superior CO2 activity and α-Fe catalyst shows higher CO selectivity. Fe3C is the less efficient phase compared to Fe5C2/α-Fe.
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Fe-based catalysts are efficient systems for CO2 conversion via reverse water-gas shift (rWGS) reaction. Nevertheless, the nature of the active phase, namely metallic iron, iron oxide or iron carbide remains a subject of debate which our paper is meant to close. Fe0 is a much better catalyst for the rWGS than Fe3C. The activity of Fe0 can be promoted by the addition of Cs and Cu whose presence hinders iron carburisation while favouring both higher conversion and enhanced selectivity. When the samples are aged in the rWGS reaction mixture during stability test a new phase appear: Fe5C2, resulting in a more active but less selective catalysts than Fe0 for the rWGS reaction. Hence our results indicate that we could potentially achieve an optimal activity/selective balance upon finely tuning the proportion Fe/Fe5C2. Beyond the fundamental information concerning active phase we have observed the presence of advanced Fischer-Tropsch-like products at ambient pressure opening new opportunities for the design of hybrid rWGS/Fischer-Tropsch systems.