Key Takeaways & Executive Findings
- •• • Fe0.3MoS/NC achieves 100% deoxygenation of 4-ethylguaiacol at 340 °C and 3 MPa H2, with 78.6% arene selectivity, outperforming MoS2/NC (83.4% deoxygenation) and enabling high-purity aromatic production for SAF blending. • • Optimal Fe/Mo molar ratio of 0.3 is critical; exceeding it inversely affects deoxygenation, indicating a narrow operational window for promoter loading. • • Real lignin conversion yields 65.5% green hydrocarbons, with C8–C16 fraction comprising 54.4% of total hydrocarbons and 63.4% aromatic content, directly meeting SAF arene concentration requirements (8–25%). • • Fe addition increases sulfur vacancy concentration and surface acidity, enhancing adsorption of oxygenates and facilitating direct deoxygenation, a mechanistic advantage over conventional Co/Ni promoters.
Abstract
Lignin, as the sole renewable source of aromatic compounds, holds significant potential for producing green aviation fuel-range arenes via hydrodeoxygenation (HDO). In this study, a series of nitrogen-doped carbon-supported FeMoS/NC bimetallic catalysts were synthesized via a hydrothermal method. The HDO performance was evaluated using 4-ethylguaiacol as a model compound at 340 °C under 3 MPa H2. The unmodified MoS2/NC catalyst achieved a deoxygenation degree of 83.4%, whereas the Fe-modified catalyst with an optimal Fe/Mo molar ratio of 0.3 (Fe0.3MoS/NC) attained complete deoxygenation (100%) with an arenes selectivity of 78.6%. Beyond this optimal ratio, the deoxygenation degree inversely correlated with the Fe/Mo molar ratio. Characterization via XRD, TEM, BET, and XPS revealed that Fe incorporation enhanced the uniform dispersion of MoS2 on the NC support, increased surface acidity, and raised the concentration of sulfur vacancies, thereby promoting adsorption of oxygen-containing compounds. The HDO pathway over Fe0.3MoS/NC primarily proceeded via direct deoxygenation. When applied to real lignin under identical conditions (340 °C, 3 MPa H2, 12 h), the catalyst yielded 65.5% green hydrocarbons, with the C8–C16 fraction accounting for 54.4% of total hydrocarbons and an aromatic selectivity of 63.4% within this fraction. These results demonstrate that Fe0.3MoS/NC is a viable catalyst for selective conversion of lignin into green arenes suitable for sustainable aviation fuel applications.
1. Introduction
Commercial hydrodeoxygenation (HDO) catalysts for lignin valorization, primarily based on sulfided CoMo or NiMo, suffer from rapid deactivation due to coking and sulfur leaching, while also exhibiting limited selectivity toward aromatic hydrocarbons in the aviation fuel range (C8–C16). The inherent complexity of lignin-derived phenolic compounds, such as 4-ethylguaiacol, demands catalysts with high deoxygenation activity and C–O bond cleavage selectivity, yet conventional catalysts often over-hydrogenate the aromatic ring, yielding saturated cyclic hydrocarbons that violate SAF seal-swell specifications. This bottleneck has hindered the economic viability of lignin-to-jet-fuel pathways.
This work addresses these limitations by introducing iron as a promoter into a nitrogen-doped carbon-supported MoS2 catalyst (FeMoS/NC). The Fe modification is shown to enhance the dispersion of MoS2, increase sulfur vacancy concentration, and modulate surface acidity, thereby promoting direct deoxygenation (DDO) over ring hydrogenation. The resulting Fe0.3MoS/NC catalyst achieves complete deoxygenation of 4-ethylguaiacol with 78.6% arene selectivity, and when applied to real lignin, produces a hydrocarbon fraction with 63.4% aromatics in the C8–C16 range, directly aligning with SAF requirements. This work establishes a robust catalytic pathway for efficient lignin-to-arene conversion, offering a promising route to sustainable aviation fuel.
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CHEN Lu, DENG Yacong, WU Zifan, QIU Yuting, YANG Xin, SUI Guoyong, LIU Bin, YU Yingmin, CHAI Yongming (2026). Fe-modified MoS2/NC catalyst for hydrodeoxygenation of lignin into aviation fuel-range arenes. Journal of Fuel Chemistry and Technology. https://doi.org/10.1016/S1872-5813(26)60644-5
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Frequently Asked Questions
What is the optimal Fe/Mo molar ratio for maximizing deoxygenation activity, and what is the penalty for exceeding it?
The optimal Fe/Mo molar ratio is 0.3, yielding 100% deoxygenation of 4-ethylguaiacol at 340 °C and 3 MPa H2. Exceeding this ratio leads to a decrease in deoxygenation degree, indicating that excess Fe may block active sites or alter the catalyst structure adversely.
How does Fe modification influence the reaction pathway for 4-ethylguaiacol HDO, and what is the resulting selectivity?
Fe modification promotes a direct deoxygenation (DDO) pathway, as evidenced by the high arene selectivity of 78.6% at complete conversion. This is attributed to increased sulfur vacancies and surface acidity, which enhance C–O bond cleavage while minimizing ring hydrogenation.
What are the key performance metrics when using real lignin as feedstock, and how do they compare to model compound studies?
With real lignin under 340 °C, 3 MPa H2, and 12 h reaction, the Fe0.3MoS/NC catalyst yields 65.5% green hydrocarbons. The C8–C16 fraction constitutes 54.4% of total hydrocarbons, with 63.4% aromatic selectivity within that fraction. These results confirm the catalyst's effectiveness on complex lignin streams, albeit with lower arene selectivity than the model compound (78.6%).
What is the industrial relevance of the aromatic content in the C8–C16 fraction for sustainable aviation fuel (SAF) applications?
SAF formulations require an arene content of 8–25% to ensure proper seal swell and fuel system compatibility. The Fe0.3MoS/NC catalyst produces a C8–C16 fraction with 63.4% aromatics, which can be blended with other SAF components to meet the required aromatic concentration, thus providing a renewable source of arenes.
How does the Fe0.3MoS/NC catalyst compare to conventional CoMo or NiMo catalysts in terms of sulfur vacancy concentration and resistance to deactivation?
The study demonstrates that Fe incorporation increases sulfur vacancy concentration and improves MoS2 dispersion, which are critical for HDO activity. While direct comparison to CoMo/NiMo is not provided, the enhanced sulfur vacancies and acidity suggest potential for improved activity and stability, though long-term deactivation studies are not reported.
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