Work

Formation and Role of Iron-Containing Phases in CO2 Hydrogenation to Higher Hydrocarbons

Year: 2025

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide The hydrogenation of CO 2 to higher hydrocarbons (C 2+ -hydrocarbons) over Fe-based catalysts represents a promising strategy for CO 2 valorization. An in-depth understanding of the restructuring of Fe-containing phases under reaction conditions and their role in product formation is necessary to enable tailored catalyst design. To this end, we introduce a simple preparation method where Fe nanoparticles (NP) are simply mixed physically with Fe 3 O 4 and/or a potassium-based promoter. To establish the direct influence of metallic Fe, Fe 3 O 4 and/or a promoter on the catalyst restructuring and performance, the as-prepared physical mixtures are used in steady-state and time-resolved kinetic tests without any pretreatment. Combined with complementary in situ characterization methods, we demonstrate that Fe 3 O 4 is not a necessary component in the initial catalyst or in the surface/bulk composition of the working catalyst to ensure efficient CO 2 conversion to CO and subsequently C 2+ -hydrocarbons formation. Instead, metallic Fe reduces CO 2 to gas-phase/surface CO species. Therefrom formed surface CO and/or C species should contribute to FeC x formation besides Fe carburization with the aid of gas-phase CO. This process is enhanced in the presence of a K-containing promoter. Its effectiveness depends on the ability of K species to migrate under reaction conditions, which is related to the type of K precursor. The catalysts based on physical mixtures of metallic Fe NP and K 2 CO 3 developed in this study outperform the majority of previous catalysts in terms of higher hydrocarbon and C 2 –C 4 olefin yield, yet suppressed CH 4 formation. Thus, our strategy and results provide the basis for the development of efficient CO 2 hydrogenation catalysts.

Source: ACS Catalysis

DOI: 10.1021/acscatal.4c07946