ACS Catalysis
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2024
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IF 11.3
Ruifeng Wang,Yusen Chen,Xin Shang,Binglian Liang,Xiong Zhang,Hongying Zhuo,Hongmin Duan,Xuning Li,Xiaofeng Yang,Xiong Su,Yanqiang Huang,Tao Zhang
Alkali metals have been extensively used as an industrial promotor with a significant impact on the iron-based Fischer–Tropsch Synthesis (FTS), while their specific roles are still ambiguous due to the difficulty in discriminating the active species, especially in a dynamic evolution under reaction conditions. In this contribution, the dependent FTS performance on alkali metal content over iron-based catalysts by precise regulation of sodium (Na) doping was scrutinized. It is found that a trace addition of Na (0.5% mass fraction) dramatically switches the hydrocarbon selectivity from alkane to alkene, giving rise to total olefin selectivity from 27 to 76%. With the help of probe experiments and operando techniques, we demonstrate that the addition of Na can hardly affect the final state of iron carbide active species, but rather changes the formation rate of iron carbide, especially at the initial reaction stage. The presence of Na plays an exclusive role in regulating the electronic properties of iron carbide and adsorption behaviors of guest molecules, thus tailoring the reaction pathway by promoting the coupling of *CH2 species while suppressing the excessive hydrogenation, which is deemed to be the intrinsic mechanism behind the high alkene selectivity. This work provides a clear-cut insight into the effect of alkali metal promotors for iron-based F–T catalytic systems as well as a theoretical basis for designing high-performance F–T catalysts.
研究领域:
化学工程
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催化科学
✓ 已验证
产品关联
DOI
高影响因子
APPLIED SURFACE SCIENCE
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2022
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IF 7.392
Minhua Zhang,Haipeng Yu,Yuzhe Sun,Yingzhe Yu,Yifei Chen,Lingtao Wang
Cobalt carbide (Co 2 C) has been discovered as the promising active phase for Fischer–Tropsch to olefins (FTO) process and higher alcohols synthesis (HAS) from syngas, in the form of nanoprisms and nanospheres, respectively. However, CO 2 formation is inevitable on Co 2 C catalysts, especially in FTO process. So far, the mechanism of CO 2 formation on Co 2 C surfaces is less understood. This work provides fundamental insights into CO 2 formation on Co 2 C nanospheres and nanoprisms through computational and experimental study. DFT calculations demonstrate that: Co 2 C (1 0 1) and (0 2 0) surfaces exposed on Co 2 C nanoprisms are basically not active for water gas shift (WGS) reactions but the introduction of Na greatly promotes CO 2 formation. CO 2 is less favored on Co 2 C(1 1 1) surface which is dominant on Co 2 C nanospheres, however, the reverse WGS activities can be promoted with Na addition. The experimental results confirmed removing Na from Co 2 C can efficiently suppress WGS activity, thus reducing CO 2 selectivity while the selectivity of light olefins retained. Though previous studies focused on Na addition to promote the yield of light olefins, our work indicates that Na also promotes undesired CO2 formation. Our results suggest that Na is crucial for active phase formation but not necessarily beneficial during the CO hydrogenation reactions.
研究领域:
化学工程
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催化科学
✓ 已验证
产品关联
DOI
高影响因子
Catalysis Science & Technology
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2025
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IF 4.2
Zhongtao Sun,Jielang Huang,Ling Zhou,Yi Zhang
The reverse water gas shift (RWGS) reaction is a critical and essential step in the CO2 hydrogenation of iron-based catalysts to produce high-value chemicals such as olefins and higher alcohols. Modification iron-based catalysts by promoter is a popular way in design efficient catalysts which not only can regulate the iron active species but also alter the CO2 adsorption and hydrogenation performance of the catalyst. Herein, a series of Na and Pd promoted 10Fe/SiO2 were prepared. 1Pd/2Na10Fe/SiO2 catalyst exhibited the highest CO2 conversion (13.2 %), the highest CO selectivity (99.7 %) and good catalyst stability. Combination of various characterization results, such as XPS, HRTEM, Mössbauer spectroscopy, CO/CO2-TPD, H2-TPD and in situ DRIFTS, it was found that the addition of Na promoter altered the reaction pathway from redox and associated pathway to only following an associative pathway, contributing to the high CO selectivity. Besides, when the content of Fe2+ species was similar, the associated pathway would be advantageous to high CO formation rate during RWGS reaction over iron-based catalysts. On the other hand, in the same reaction pathway, the content of Fe2+ species would determine the CO formation rate over iron-based catalysts during RWGS reaction.
研究领域:
催化化学
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材料科学
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环境科学
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产品关联
DOI
高影响因子
FUEL
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2024
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IF 6.7
Wenxia Zhang,Hongtao Zhang,Mohamed Abbas,Juan Zhang,Zhijun Huang,Sibudjing Kawi,Jiangang Chen
The advancement of large-scale and environmentally-friendly solid-state synthesis methods is of paramount importance for the production of precipitated catalysts, notably Fe-based catalysts utilized in Fischer-Tropsch synthesis (FTS). In this study, we present an innovative solvent-independent, wastewater-free solid-state approach for the synthesis of highly efficient Fe/ZrO 2 catalysts, elucidating the mechanisms of promotion within this specific methodology. The prepared catalysts underwent rigorous evaluation under industrially-relevant FTS conditions (230–270 °C, 20 bar, and WHSV = 5400 mL/(g cat ⋅h)). A comprehensive suite of characterization techniques was employed to establish the intricate interplay between catalytic activity and structural attributes. We meticulously examined the impact of Na as an alkali promoter and the role of transition metals (Cu and Mn) in enhancing FTS catalytic performance. The catalytic outcomes obtained clearly demonstrate the pivotal role of the synergistic interaction between Mn and Na within the Na-Mn-Fe/ZrO 2 catalyst system in driving the FTS reaction. This synergism significantly enhances FTS performance, yielding an impressive CO conversion rate (89.91 %) while maintaining low selectivity to CH 4 (7.75 %). The incorporation of Mn and Na into the catalyst matrix enhances the dispersion of Fe 2 O 3 , thereby improving the reducibility of Mn/Fe oxides and elevating the electron density on the catalyst surface. These factors facilitate the formation of active Hägg iron carbide (χ-Fe 5 C 2 ), stimulating chain propagation and ultimately leading to the generation of valuable C 5+ hydrocarbon products, which underscores its potential as an optimal candidate for future industrial applications in Fe-based Fischer-Tropsch synthesis.
研究领域:
催化
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化学工程
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环境科学
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材料科学
✓ 已验证
产品关联
DOI
高影响因子
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