The role of H2 in Fe carburization by CO in Fischer-Tropsch catalysts

Chai, Jiachun; Pestman, Robert; Chen, Wei; Dugulan, A. Iulian; Feng, Bo; Men, Zhuowu; Wang, Peng; Hensen, Emiel J. M.

doi:10.1016/j.jcat.2021.05.027

Cited by 20 publications

(26 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The C content of in situ formed Fe carbide as determined by TPH is shown in Figure . The evolution of the C/Fe ratio with carburization time is very similar to the results in our previous work . We also used Mössbauer spectroscopy to study the phase composition of Raney-Fe as a function of the duration of carburization under similar conditions.…”

Section: Resultssupporting

confidence: 81%

“…This sample contains 70% ε(′)-carbide and 25% χ-Fe 5 C 2 . Under these carburization conditions, ε(′)-carbide is more stable than χ-Fe 5 C 2 as reported before . Notably, no Fe oxides are observed during the carburization process, which indicates that O removal from the surface as either H 2 O or CO 2 is fast compared to C removal.…”

Section: Resultssupporting

confidence: 74%

“…The evolution of the C/Fe ratio with carburization time is very similar to the results in our previous work. 25 We also used Mossbauer spectroscopy to study the phase composition of Raney-Fe as a function of the duration of carburization under similar conditions. Mossbauer spectra were recorded at −153 °C to determine the relative contributions of the various Fe species.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Under these carburization conditions, ε(′)carbide is more stable than χ-Fe 5 C 2 as reported before. 25 Notably, no Fe oxides are observed during the carburization process, which indicates that O removal from the surface as either H 2 O or CO 2 is fast compared to C removal. In the following, we refer to all ε(′)and χ-Fe 5 C 2 phases collectively as Fe carbides.…”

Section: T H I S C O N T E N T Imentioning

confidence: 97%

See 3 more Smart Citations

Isotopic Exchange Study on the Kinetics of Fe Carburization and the Mechanism of the Fischer–Tropsch Reaction

et al. 2022

Self Cite

View full text Add to dashboard Cite

The kinetics of the transformation of metallic Fe to the active Fe carbide phase at the start of the Fischer–Tropsch (FT) reaction were studied. The diffusion rates of C atoms going in or out of the lattice were determined using 13C-labeled synthesis gas in combination with measurements of the transient 12C and 13C contents in the carbide by temperature-programmed hydrogenation. In the initial 20 min, C diffuses rapidly into the lattice occupying thermodynamically very stable interstitial sites. The FT reaction starts already during these early stages of carburization. When reaching steady state, the diffusion rates of C in and out of the lattice converge and the FT reaction continues via two parallel reaction mechanisms. It appears that the two outer layers of the Fe carbide are involved in hydrocarbon formation via a slow Mars–Van Krevelen-like reaction contributing to ∼10% of the total activity, while the remainder of the activity stems from a fast Langmuir–Hinshelwood reaction occurring over a minor part of the catalyst surface.

show abstract

Section: Resultssupporting

confidence: 81%

Section: Resultssupporting

confidence: 74%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: T H I S C O N T E N T Imentioning

confidence: 97%

See 2 more Smart Citations

Isotopic Exchange Study on the Kinetics of Fe Carburization and the Mechanism of the Fischer–Tropsch Reaction

et al. 2022

Self Cite

View full text Add to dashboard Cite

show abstract

“…A broad peak in the second region between 400 • C and 600 • C relates to the reduction of iron carbide and a part of the iron oxide species to α-Fe (Equation ( 6)), since the Fe 5 C 2 can be transformed to α-Fe. Peaks at temperatures higher than 600 • C correlate to the deposited carbon on α-Fe from the Boudouard reaction (Equation ( 7)) [36][37][38][39]. Our results are in good agreement with Tahari et al [39], who has suggested a three-step sequential process for the carbonization of the Fe/SiO 2 catalyst (Fe 2 O 3 → Fe 3 O 4 → FeO → α-Fe).…”

Section: Reduction Of Iron Oxidesupporting

confidence: 90%

Effect of Different Iron Phases of Fe/SiO2 Catalyst in CO2 Hydrogenation under Mild Conditions

et al. 2022

View full text Add to dashboard Cite

The effect of different active phases of Fe/SiO₂ catalyst on the physio-chemical properties and the catalytic performance in CO₂ hydrogenation under mild conditions (at 220 °C under an ambient pressure) was comprehensively studied in this work. The Fe/SiO₂ catalyst was prepared by an incipient wetness impregnation method. Hematite (Fe₂O₃) in the calcined Fe/SiO₂ catalyst was activated by hydrogen, carbon monoxide, and hydrogen followed by carbon monoxide, to form a metallic iron (Fe/SiO₂-h), an iron carbide (Fe/SiO₂-c), and a combination of a metallic iron and an iron carbide (Fe/SiO₂-hc), respectively. All activated catalysts were characterized by XRD, Raman spectroscopy, N₂ adsorption–desorption, H₂-TPR, CO-TPR, H₂-TPD, CO₂-TPD, CO-TPD, NH₃-TPD, and tested in a CO₂ hydrogenation reaction. The different phases of the Fe/SiO₂ catalyst are formed by different activation procedures and different reducing agents (H₂ and CO). Among three different activated catalysts, the Fe/SiO₂-c provides the highest CO₂ hydrogenation performance in terms of maximum CO₂ conversion, as well as the greatest selectivity toward long-chain hydrocarbon products, with the highest chain growth probability of 0.7. This is owing to a better CO₂ and CO adsorption ability and a greater acidity on the carbide form of the Fe/SiO₂-c surface, which are essential properties of catalysts for polymerization in FTs.

show abstract

Operando DRIFTS Investigations on Surface Intermediates and Effects of Potassium in CO₂ Hydrogenation over a K−Fe/YZrO_x Catalyst

Fedorova,

Kraußer,

Weiß

et al. 2024

ChemCatChem

View full text Add to dashboard Cite

A detailed operando DRIFTS study on the CO2 Fischer‐Tropsch reaction with K‐promoted Fe/YZrOx catalysts was performed to investigate the influence of this modification on the catalytic performance in the formation of lower olefins as well as higher hydrocarbons and to gain insights into mechanistic aspects. Catalytic testing revealed an enhanced formation of olefins and hydrocarbons by adding potassium to the catalysts, while spectroscopic studies revealed various stable adsorbates and intermediates such as monodentate carbonates, bicarbonates, formates, formyl, and methoxy on the surface of the K‐promoted Fe/YZrOx catalysts compared to the unpromoted one. Based on gas‐feed switching experiments and statistical analysis of literature IR data regarding Fe‐containing catalysts, it was found that monodentate carbonate species interacting with H2 are transformed to higher hydrocarbons and methane via formate and formyl formation, while bicarbonate species are decomposed accompanied by the formation of CO, which then further reacts to form formate or formyl and finally hydrocarbons.

show abstract

The role of H2 in Fe carburization by CO in Fischer-Tropsch catalysts

Cited by 20 publications

References 47 publications

Isotopic Exchange Study on the Kinetics of Fe Carburization and the Mechanism of the Fischer–Tropsch Reaction

Isotopic Exchange Study on the Kinetics of Fe Carburization and the Mechanism of the Fischer–Tropsch Reaction

Effect of Different Iron Phases of Fe/SiO2 Catalyst in CO2 Hydrogenation under Mild Conditions

Operando DRIFTS Investigations on Surface Intermediates and Effects of Potassium in CO₂ Hydrogenation over a K−Fe/YZrO_x Catalyst

Contact Info

Product

Resources

About

The role of H2 in Fe carburization by CO in Fischer-Tropsch catalysts

Cited by 20 publications

References 47 publications

Isotopic Exchange Study on the Kinetics of Fe Carburization and the Mechanism of the Fischer–Tropsch Reaction

Isotopic Exchange Study on the Kinetics of Fe Carburization and the Mechanism of the Fischer–Tropsch Reaction

Effect of Different Iron Phases of Fe/SiO2 Catalyst in CO2 Hydrogenation under Mild Conditions

Operando DRIFTS Investigations on Surface Intermediates and Effects of Potassium in CO2 Hydrogenation over a K−Fe/YZrOx Catalyst

Contact Info

Product

Resources

About

Operando DRIFTS Investigations on Surface Intermediates and Effects of Potassium in CO₂ Hydrogenation over a K−Fe/YZrO_x Catalyst