Dynamics of Reaction‐Induced Changes of Model‐Type Iron Oxide Phases in the CO2‐Fischer‐Tropsch‐Synthesis. Issue 14 (16th May 2022)

• Record Type: Journal Article
• Authors: Arinchtein, Aleks; Ye, Meng‐Yang; Yang, Qingxin; Kreyenschulte, Carsten; Wagner, Andreas; Frisch, Marvin; Brückner, Angelika; Kondratenko, Evgenii; Kraehnert, Ralph
• Is Part Of: ChemCatChem. Volume 14:Issue 14(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-05-16
• Subjects: CO2-FTS -- iron catalysts -- dynamic changes -- mesoporous materials -- Auger -- XPS -- STEM-EELS; Catalysis -- Periodicals; 541.39505
• DOI: 10.1002/cctc.202200240
• Languages: English
• ISSNs: 1867-3880

Abstract

Abstract: Iron‐based catalysts are employed in CO2 ‐FTS due to their ability to convert CO2 into CO in a first step and their selectivity towards higher hydrocarbons in a second CO hydrogenation step. According to the literature, iron carbides represent the active phase for hydrocarbon formation and are claimed to emerge in the presence of CO. We propose nanostructured FeOx films as model systems to assess information about the complex phase transformations during CO2 ‐FTS. Mesoporous hematite, ferrihydrite, maghemite, maghemite/magnetite films were exposed to CO2 ‐FTS atmospheres at 20 bar and 300 °C. Up to three distinct phases were observed depending on the time‐on‐stream (TOS): a sintered maghemite/magnetite phase, a carbidic core‐shell structure, and a low‐crystalline, needle‐type oxide phase. Our findings indicate that the formation of an intermediary maghemite/magnetite phase, predominant after short TOS (30 h), precedes the evolution of the carbide phase. Yet, even after prolonged TOS (185 h), no full conversion into a bulk carbide is observed. Abstract : Dynamic phase transformations of mesoporous iron oxide films in the CO2 ‐FTS at 300 °C and 20 bar. Carbide structures, resolved by STEM‐EELS, evolve after >30 h TOS and coexist with oxidic phases of different morphologies. This work provides insights into the complex formation mechanism of iron oxides in the CO2 ‐FTS.