Catalytic Behavior and Phase Composition Change of Iron Catalyst in Hydrogenation of Carbon Dioxide

抄録

Hydrogenation of CO₂ was conducted on iron catalyst under various reaction conditions to explore the catalytic behavior and the change of bulk phase composition. It was found by the use of Mössbauer spectroscopy that the metallic iron phase was transformed to a mixture of magnetite and carbides progressively during the course of reaction. The formation of Fe₃O₄ phase became more favorable under conditions which led to a high H₂O partial pressure on the catalyst bed. On the other hand, the carburization of iron catalyst was enhanced at higher temperature, with χ-Fe₅C₂ phase being predominant over θ-Fe₃C phase. Due to the fact that H₂O produced in the Fischer–Tropsch reaction also contributes to the equilibrium of the reverse water–gas shift reaction, the common product H₂O of these two steps plays a major role in suppression of overall CO₂ conversion level.