Valorization of Coal Fly Ash into Fe-FAU Catalysts: Targeted Iron Recovery and Fly Ash Matrix Effects in Methane-to-Methanol Conversion
- 1Middle East Technical University , , ,
Abstract
The valorization of industrial wastes into functional catalysts offers a route toward more sustainable chemical processes, particularly when the inherited complexity of the waste can be retained as a design variable. Here, coal fly ash was converted into Fe-FAU zeolite catalysts through an integrated waste-to-catalyst strategy in which the same industrial residue supplied both the framework-forming Si–Al fraction and the recoverable Fe precursor. During presynthesis acid treatment, Fe was selectively recovered as crystalline Fe(II) oxalate dihydrate, while the remaining aluminosilicate fraction was transformed into OSDA-free FAU zeolites and subsequently modified by recovered-Fe ion exchange and steaming. Using fly ashes with distinct inherited chemical environments, we show that source-dependent matrix effects govern framework evolution, acidity redistribution, Fe speciation, and catalytic behavior in N2O-assisted methane-to-methanol conversion. Isolated Fe3+-rich catalysts exhibited the highest initial methanol formation rate of 137 μmol gcat–1 h–1, but showed rapid activity loss associated with accessible acidity and coke formation. In contrast, the Ca-richer Fe-Z2 matrix moderated acid-site accessibility, favored small extra-framework Fe–oxo/hydroxo descriptors, and delivered stable methanol productivity of approximately 71.5 μmol gcat–1 h–1 with suppressed coke formation. Catalysts more susceptible to steaming-induced dealumination or Fe2O3-like aggregation showed lower sustained methanol productivity. Overall, this work links Fe recovery, OSDA-free FAU synthesis, recovered-Fe incorporation, and MTM catalysis in a single material-flow concept, demonstrating that fly ash acts not as a passive precursor but as a chemically active matrix that controls Fe-site distribution, acidity, and time-on-stream stability.
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BibTeX
@article{akın2026valorization,
title = {{Valorization of Coal Fly Ash into Fe-FAU Catalysts: Targeted Iron Recovery and Fly Ash Matrix Effects in Methane-to-Methanol Conversion}},
author = {Süleyman Şener Akın and Selin Cansu Gölboylu and İlhan Duruk and Can Barkın Dericioğlu and Bahar İpek and Burcu Akata},
journal = {ACS Omega},
year = {2026},
month = oct,
doi = {10.1021/acsomega.6c09000},
url = {https://pubs.acs.org/acsodf/article/doi/10.1021/acsomega.6c09000/5457792/Valorization-of-Coal-Fly-Ash-into-Fe-FAU-Catalysts},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Valorization of Coal Fly Ash into Fe-FAU Catalysts: Targeted Iron Recovery and Fly Ash Matrix Effects in Methane-to-Methanol Conversion
AU - Süleyman Şener Akın
AU - Selin Cansu Gölboylu
AU - İlhan Duruk
AU - Can Barkın Dericioğlu
AU - Bahar İpek
AU - Burcu Akata
PY - 2026
DA - 2026/10/24
JO - ACS Omega
DO - 10.1021/acsomega.6c09000
UR - https://pubs.acs.org/acsodf/article/doi/10.1021/acsomega.6c09000/5457792/Valorization-of-Coal-Fly-Ash-into-Fe-FAU-Catalysts
AB - The valorization of industrial wastes into functional catalysts offers a route toward more sustainable chemical processes, particularly when the inherited complexity of the waste can be retained as a design variable. Here, coal fly ash was converted into Fe-FAU zeolite catalysts through an integrated waste-to-catalyst strategy in which the same industrial residue supplied both the framework-forming Si–Al fraction and the recoverable Fe precursor. During presynthesis acid treatment, Fe was selectively recovered as crystalline Fe(II) oxalate dihydrate, while the remaining aluminosilicate fraction was transformed into OSDA-free FAU zeolites and subsequently modified by recovered-Fe ion exchange and steaming. Using fly ashes with distinct inherited chemical environments, we show that source-dependent matrix effects govern framework evolution, acidity redistribution, Fe speciation, and catalytic behavior in N2O-assisted methane-to-methanol conversion. Isolated Fe3+-rich catalysts exhibited the highest initial methanol formation rate of 137 μmol gcat–1 h–1, but showed rapid activity loss associated with accessible acidity and coke formation. In contrast, the Ca-richer Fe-Z2 matrix moderated acid-site accessibility, favored small extra-framework Fe–oxo/hydroxo descriptors, and delivered stable methanol productivity of approximately 71.5 μmol gcat–1 h–1 with suppressed coke formation. Catalysts more susceptible to steaming-induced dealumination or Fe2O3-like aggregation showed lower sustained methanol productivity. Overall, this work links Fe recovery, OSDA-free FAU synthesis, recovered-Fe incorporation, and MTM catalysis in a single material-flow concept, demonstrating that fly ash acts not as a passive precursor but as a chemically active matrix that controls Fe-site distribution, acidity, and time-on-stream stability.
SN - 2470-1343
ER -