Key Takeaways & Executive Findings
- •• • DFT calculations reveal that manganese addition increases the thermodynamic barrier for carbon permeation into Fe-Mn alloy surfaces compared to pure iron, as evidenced by less favorable energetics for subsurface carbon occupancy. • • Minima-hopping structural searches confirm that within the considered carbon coverage range, no surface reconstructions leading to iron carbide phases occur, indicating that early carburization stages do not spontaneously form active carbide surfaces. • • Electronic structure analysis shows that carbon deposition modulates the d-band centers of metal surfaces, but manganese suppresses the shift toward values characteristic of bulk iron carbides, explaining the hindered carburization. • • The study provides atomic-scale mechanistic insight into the role of manganese as a promoter, which is critical for optimizing Fe-Mn catalysts in industrial FTS processes where product selectivity and catalyst stability are paramount.
Abstract
Fe-Mn catalysts have attracted considerable attention for industrial Fischer-Tropsch synthesis (FTS) due to their ability to modulate product spectra. Carbon adsorption and permeation on catalyst surfaces are critical elementary steps in the in situ formation of active iron carbide phases. Here, density functional theory (DFT) calculations systematically investigate the atomistic structures, thermodynamic stabilities, and electronic properties of carbon-deposited Fe-Mn alloy surfaces at the early stage of carburization. These surfaces exhibit distinct thermodynamic sensitivity to carbon atoms adsorbed on the surface and permeating into interstitial sites. By combining DFT with minima-hopping structural searches, we demonstrate that the initial stage of carbon permeation cannot trigger surface reconstruction to form iron carbide phases. The addition of manganese thermodynamically hinders carbon permeation. Although deposited carbon atoms modulate the electronic structure of metals, manganese retards the shift of d-band centers toward those of bulk iron carbide phases. This study provides atomic-scale insight into the in situ evolution of Fe-Mn catalyst surfaces during carbon deposition, indicating that manganese promoter has a noticeable effect on carbon permeation.
1. Introduction
Fischer-Tropsch synthesis (FTS) remains a cornerstone for converting syngas derived from coal, natural gas, or biomass into clean liquid fuels and chemicals. Iron-based catalysts are particularly attractive due to their intrinsic water-gas shift activity, broad operating range, and low cost. However, industrial iron catalysts typically comprise a complex mixture of iron and iron carbide phases, and their performance is highly sensitive to the in situ formation of active carbides. The addition of promoters, such as manganese, is known to effectively manipulate the FTS product spectrum, yet the fundamental mechanisms by which manganese alters the carburization process remain poorly understood. This lack of atomic-scale knowledge hinders rational catalyst design and process optimization.
This study addresses this bottleneck by employing first-principles density functional theory (DFT) to systematically investigate the early stages of carbon adsorption and permeation on Fe-Mn alloy surfaces. By combining DFT with minima-hopping structural searches, the authors provide a detailed thermodynamic and electronic analysis of carbon-deposited surfaces. The findings reveal that manganese thermodynamically hinders carbon permeation and suppresses the evolution of d-band centers toward those of bulk iron carbides. These insights are crucial for understanding how manganese promoters influence the activation and performance of iron-based FTS catalysts, offering a pathway to more precise control over catalyst structure and reactivity.
Loading authentic research manuscript (Pages 1–5)...
YANG Tao, MA Huan, LIU Xingchen (2026). Manganese Promoter Hinders Carbon Permeation on Iron-Based Catalyst Surfaces: A First-Principles Study. Journal of Fuel Chemistry and Technology. https://doi.org/10.1016/S1872-5813(26)60657-3
Research & Educational Purpose Only: The translations, structured abstracts, analytical annotations, and data reports provided by SinoGreenTechare intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoGreenTech claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the specific thermodynamic effect of manganese on carbon permeation in Fe-Mn alloy surfaces compared to pure iron?
The DFT calculations show that manganese addition makes carbon permeation thermodynamically less favorable. The presence of manganese increases the energy cost for carbon atoms to occupy subsurface interstitial sites, thereby hindering the initial stages of carburization.
Does the early stage of carbon permeation induce surface reconstruction to form iron carbide phases?
No. Minima-hopping structural searches within the considered carbon coverage range found no surface reconstructions leading to iron carbide phases. This indicates that the initial carbon permeation does not spontaneously trigger the formation of active carbide surfaces.
How does carbon deposition affect the electronic structure of Fe-Mn surfaces, and what role does manganese play?
Carbon deposition modulates the electronic states of metal surfaces, shifting d-band centers. However, manganese suppresses this shift, retarding the evolution of d-band centers from those of iron surfaces toward bulk iron carbide phases. This electronic effect correlates with the hindered carbon permeation.
What are the practical implications of these findings for the design of Fe-Mn Fischer-Tropsch catalysts?
Understanding that manganese hinders carbon permeation can guide the optimization of catalyst composition and pretreatment conditions. By controlling manganese content, one can potentially tune the extent of carburization and thus the active phase formation, impacting product selectivity and catalyst lifetime in industrial FTS.
Related Chinese Research & Cross-Citations
Recent Advances in Carbon-Based Materials for CO2 Capture and Utilization
CO2 capture and utilization (CCU) technologies are critical for mitigating global warming and promoting resource circularity. Carbon-based materials, with tunable pore structures, abundant active sites, high specific surface area, and excellent chemical stability, show significant potential for CO2 capture and conversion. This review systematically analyzes the adsorption behaviors and performance variations of activated carbon, porous carbon, graphene, and carbon nanotubes in CO2 capture. For utilization, recent advances in catalytic applications for methanation, reverse water-gas shift (RWGS), dry reforming of methane (DRM), and alcohol synthesis are emphasized. The benefits and drawbacks of carbon materials regarding adsorption capacity, catalytic activity, and stability are evaluated, and their potential in integrated CCU technologies is discussed. Key strategies for enhancing performance through structural modulation and surface modification are elucidated. This review provides theoretical guidance for future development and large-scale implementation of carbon-based materials in CCU.
Fabrication and Microwave Absorption Performance of FexOy/TiO2/C Composites Derived from Red Mud
Red mud, an industrial solid waste from alumina production, poses severe environmental challenges. This study presents a resource-efficient strategy to convert red mud into high-performance microwave absorbing materials. FexOy/TiO2/C composites were synthesized via a sol-gel method using starch as carbon source, followed by carbothermal reduction. The phase composition and microstructure were optimized by adjusting calcination temperature and raw material ratio. The optimal sample, RmCT-5.4-700, exhibited a minimum reflection loss (RLmin) of -30.2 dB at 14.0 GHz with an effective absorption bandwidth (EAB) of 5.3 GHz at a coating thickness of 2.0 mm. The superior absorption performance is attributed to the synergistic effects of dielectric components (TiO2, graphitized carbon) and magnetic components (Fe3O4/Fe). Carbothermal reduction introduces defects that induce dipole polarization, while the conductive network formed by graphitized carbon and Fe3O4/Fe particles enhances conductive loss. Heterogeneous interfaces between Fe3O4, Fe, TiO2, and the red mud matrix promote interfacial polarization. The magnetic loss of Fe3O4/Fe improves impedance matching, facilitating electromagnetic wave penetration and absorption. This work not only provides a novel route for red mud valorization but also contributes to the high-value utilization of solid wastes.
Damage Mechanism of High Chromia Refractory in the Slag Tapping Hole of Commercial Entrained-Flow Gasifiers
The service life of refractory bricks in the slag tapping hole of entrained-flow gasifiers is a critical bottleneck for long-term stable operation. This study investigated the damage mechanism of high chromia refractories in four commercial coal-water slurry gasifiers by analyzing gasification coal samples and corroded refractory bricks. Slag characteristics, including crystallization and viscosity-temperature behavior, were evaluated. Results revealed that low-viscosity slag induces more severe refractory damage. To mitigate slag crystallization risk, a safe slag tapping temperature range is recommended as tICT−t2.5 when tICT exceeds t25. Interior morphology of corroded bricks exhibited cracks, primarily attributed to molten slag penetration and subsequent reactions with refractory material. SEM-EDS analysis of slag-aggregate and slag-matrix interfaces identified reduction in Cr2O3 content as the earliest damage characteristic. XRD detected no zirconium-containing spinel in cracks, indicating that thermal expansion mismatch between newly formed phases and the refractory matrix drives crack propagation. A damage mechanism is proposed: initial Cr2O3 depletion compromises both matrix and aggregate, facilitating slag ingress and new phase formation, ultimately leading to structural failure. Early detection or prevention of Cr2O3 reduction is essential to prolong refractory service life.
Research advances in the pyrolysis recycling of waste wind turbine blades
The global energy landscape is undergoing a profound transformation, with wind energy gaining increasing prominence due to its clean and renewable nature. However, as installed wind power capacity expands, disposal of waste wind turbine blades (WWTB) has emerged as a significant challenge. These blades are predominantly composed of epoxy resin (EP) polymers, carbon fibers (CFs), and glass fibers (GFs). Improper disposal exacerbates environmental concerns and leads to loss of valuable resources, particularly carbon-based materials. Pyrolysis technology, a versatile and environmentally sustainable method for resource recovery, has garnered considerable attention for WWTB disposal. This work presents a comprehensive review of pyrolytic recycling of WWTB, focusing on principles and classifications of pyrolysis technology, key factors influencing the pyrolysis process, as well as pyrolysis methods, equipment, products, and their applications. Through in-depth analysis of current research, this review identifies critical unresolved issues and provides a forward-looking perspective on emerging research trends. The review highlights that pyrolysis can effectively recover glass fibers and carbon fibers with mechanical property retention depending on process conditions, and that catalytic pyrolysis can enhance the quality of recovered products. Economic analysis indicates that collaborative disposal methods can improve cost-effectiveness. Future research should focus on optimizing process parameters for large-scale industrial application and developing more efficient catalysts to improve product selectivity and fiber quality.
Citric Acid-Modified HUSY Zeolite Catalyzes Alkylation of Phenol with Cyclohexanol for High-Density Aviation Fuel Precursors
Lignin-derived oxygenated aromatics, particularly phenols and aromatic ethers, are promising feedstocks for synthesizing high-density, high-heat-sink aviation fuels via alkylation-hydrogenation processes. This study systematically evaluates the catalytic performance of various zeolites (Hβ, HZSM-5, MCM-41, and HUSY) in the alkylation of phenol with cyclohexanol. Characterization demonstrates that HUSY zeolite exhibits superior catalytic activity due to its favorable pore architecture and well-balanced acid site distribution, which synergistically facilitate molecular diffusion and catalytic transformations. To further enhance catalytic properties, HUSY was modified with citric acid at various concentrations and compared with NaOH and oxalic acid treatments. Results reveal that citric acid treatment preserves crystallinity while modulating acidity and pore structure. All modified zeolites enhance phenol alkylation activity. Notably, HUSY-0.5M, exhibiting the highest medium-strong acid to total acid ratio, achieves superior performance: 80.4% phenol conversion and 99.6% selectivity for alkylation products. The catalyst also shows high activity for various lignin-derived compounds (p-cresol, anisole, guaiacol), demonstrating broad applicability. This work provides a new strategy for valorizing lignin-derived phenols into high-value fuel precursors through alkylation.
Hydrogen Production and Structure Evolution Mechanism during Thermochemical Conversion of Microalgae Pellet in Molten Hydroxide Salts
This study investigates the thermochemical conversion behavior of microalgae pellets in a molten hydroxide salt (80% NaOH-20% Na2CO3) system and its influence on hydrogen production. By comparing temperature evolution, gas release characteristics, and structural evolution of pellets with and without molten salt, and integrating char alkalization experiments, the regulatory mechanism of molten salt on reaction pathways and hydrogen production was systematically analyzed. Results indicate that molten salt significantly enhances internal heat transfer efficiency, achieving a central heating rate of 177 °C/s, effectively alleviating thermal hysteresis. Concurrently, molten salt promotes pore development through penetration, erosion, and catalytic effects, resulting in a porosity increase of 53.2%–104.3% after 10 s of reaction. Conversion efficiency is markedly improved, with the dominant reaction pathway shifting to char alkalization after only 70 s. Furthermore, when heating rate is increased above 600 °C, hydrogen yield from char alkalization improves more significantly, primarily attributed to the synergistic promotion of molten salt catalysis and rapid heating on volatiles reforming. This study provides a theoretical foundation for understanding efficient hydrogen production from biomass in molten hydroxide salts.