Activity and Structural Changes of Fe‐based Catalysts during CO₂ Hydrogenation towards CH₄ – A Mini Review

Abstract

Heterogeneous iron catalysts are active in the hydrogenation of carbon oxides and are widely investigated for the production of long‐chained hydrocarbons according to the Fischer‐Tropsch synthesis. Moreover, high selectivity of light hydrocarbons, such as CH4, also occurs strongly depending on reaction conditions and catalyst formulations. As a consequence, Fe catalysts reveal promising methanation activity as referred to the traditional Ni catalysts. Additionally, Fe catalysts also benefit from their low price and toxicological harmlessness. However, the dynamic behavior of iron upon CO2 hydrogenation is not yet unraveled unambiguously including phase transformations, structural changes and participation of carbon species formed. The present review highlights these complex processes of Fe catalysts with special focus on the methanation of CO2. Additionally, different analytical tools useful for ex situ and in situ studies are critically evaluated.

Transforming carbon dioxide into jet fuel using an organic combustion-synthesized Fe-Mn-K catalyst

“…According to the literature and our own results, the carburization process of Fe nanoparticles during the catalytic reaction forms the Fe carbide phase, which through a FT pathway favours the C–C condensation reactions to produce large hydrocarbons within the range of aviation fuel. In our experiments, the χ-Fe 5 C 2 was formed during the catalyst activation/reduction process, in the beginning of the reaction what it is happening is mainly CO 2 methanation reaction on χ-Fe 5 C 2 , the relatively high pressure of water can then oxidize on χ-Fe 5 C 2 to Fe 3 O 4 , and the Fe 3 O 4 was simultaneously carburized by CO 80 . In model experiments, Fe 2 O 3 was produced from the oxidation of Fe 3 O 4 by CO 2 /H 2 O, and Fe 2 O 3 was steadily reduced to Fe 3 O 4 by H 2 in the reaction system (Supplementary Fig.…”

Iron Based Core-Shell Structures as Versatile Materials: Magnetic Support and Solid Catalyst

“…V total = 100 mL STP /min) for 12 h to achieve a defined and reproducible catalyst state. This is necessary, due to the well-known dynamic changes of iron phases during synthesis gas reactions [6]. In the following, CO 2 hydrogenation was performed at 350, 370, and 390 • C (H 2 /CO 2 = 4.5, p = 1 bar, .…”

“…Iron is a suitable core material in core-shell structures due to its large-scale availability and sustainability, as it can replace ecologically harmful or rare metals. In catalytic processes, such as the power-to-methane process, it is considered a promising replacement for nickel and cobalt as active materials, as it provides high selectivity in the methanation 2 of 16 step [6] and flexibility toward various mixtures of H 2 /CO/CO 2 . The limited reactivity and the formation of different carbonaceous species under reaction conditions, however, is still a challenge, which is a matter of ongoing research [7,8].…”

The Role of Alkali and Alkaline Earth Metals in the CO2 Methanation Reaction and the Combined Capture and Methanation of CO2

“…Finally, Mg has been indicated as a suitable promoter for Fe catalysts during CO 2 methanation [72]. Fe catalysts, commonly known to be active during the Fischer-Tropsch synthesis, could also be viable candidates for the CO 2 hydrogenation into CH 4 under high pressure, after the incorporation of a suitable promoter [73]. Baysal et al [72] incorporated a series of 15 different promoters on a commercial α-Fe 2 O 3 powder via incipient wetness.…”