Elucidating reaction pathways occurring in CO2 hydrogenation over Fe-based catalysts

A detailed experimental analysis of reaction pathways proceeding in CO2 hydrogenation over Fe-based catalysts was performed. The catalytic activity was measured at different degrees of conversion and used to analyze the production/consumption rates of reagents and products along the catalyst bed. It was demonstrated that except for the reverse water gas shift reaction and the subsequent hydrogenation of CO via Fischer-Tropsch (FT) mechanism, additional routes of hydrocarbon formation from CO2 exist in the CO2 hydrogenation. One of them is the methanation reaction which takes place over all studied catalysts. Another one is a direct pathway of C2+ hydrocarbon formation from CO2 that plays a significant role at least for some catalysts. In this route, iron carbides may be responsible for hydrogenating CO2 into C2+ hydrocarbons. Based on these results, the concept of requiring iron oxides as an essential active component for catalyzing the RWGS reaction in CO2-FT should be reviewed.