Effect of alkalis on iron-based Fischer-Tropsch synthesis catalysts: Alkali-FeOx interaction, reduction, and catalytic performance

Li, Jifan; Cheng, Ximing; Zhang, Chenghua; Chang, Qiang; Wang, Jue; Wang, Xiaoping; Lv, Zhengang; Dong, Wen‐Sheng; Yang, Yong; Li, Yongwang

doi:10.1016/j.apcata.2016.10.006

Cited by 86 publications

(62 citation statements)

References 42 publications

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“…Yet, at 230 • C, which slowed the carburization rate of the catalyst, the addition of water oxidized the iron carbides, and FTS activity was lost. Recent TPR-EXAFS/XANES investigations by Ribeiro et al [35] and Li et al [158] indicate that the addition of alkali promotes the carburization rate of iron catalysts.…”

Section: Hydrocarbonsmentioning

confidence: 99%

Fischer–Tropsch: Product Selectivity–The Fingerprint of Synthetic Fuels

et al. 2019

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The bulk of the products that were synthesized from Fischer–Tropsch synthesis (FTS) is a wide range (C1–C70+) of hydrocarbons, primarily straight-chained paraffins. Additional hydrocarbon products, which can also be a majority, are linear olefins, specifically: 1-olefin, trans-2-olefin, and cis-2-olefin. Minor hydrocarbon products can include isomerized hydrocarbons, predominantly methyl-branched paraffin, cyclic hydrocarbons mainly derived from high-temperature FTS and internal olefins. Combined, these products provide 80–95% of the total products (excluding CO2) generated from syngas. A vast number of different oxygenated species, such as aldehydes, ketones, acids, and alcohols, are also embedded in this product range. These materials can be used to probe the FTS mechanism or to produce alternative chemicals. The purpose of this article is to compare the product selectivity over several FTS catalysts. Discussions center on typical product selectivity of commonly used catalysts, as well as some uncommon formulations that display selectivity anomalies. Reaction tests were conducted while using an isothermal continuously stirred tank reactor. Carbon mole percentages of CO that are converted to specific materials for Co, Fe, and Ru catalysts vary, but they depend on support type (especially with cobalt and ruthenium) and promoters (especially with iron). All three active metals produced linear alcohols as the major oxygenated product. In addition, only iron produced significant selectivities to acids, aldehydes, and ketones. Iron catalysts consistently produced the most isomerized products of the catalysts that were tested. Not only does product selectivity provide a fingerprint of the catalyst formulation, but it also points to a viable proposed mechanistic route.

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Section: Hydrocarbonsmentioning

confidence: 99%

Fischer–Tropsch: Product Selectivity–The Fingerprint of Synthetic Fuels

et al. 2019

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“…After applying a H 2 reduction treatment, both the UP and NaÀ S catalysts are well reduced into α-Fe. This observation is valid regardless of the reduction retarding effect of alkali in the NaÀ S catalysts, [49] and possible catalyst material re-oxidation upon exposure of zerovalent Fe to air. [46,47,50] All catalysts under study were cooled down under N 2 or N 2 : H 2 flow and flushed with N 2 at room temperature for a period of time, without a dedicated passivation step.…”

Section: Effect Of H 2 Reductionmentioning

confidence: 66%

Identification of Iron Carbides in Fe(−Na−S)/α‐Al₂O₃ Fischer‐Tropsch Synthesis Catalysts with X‐ray Powder Diffractometry and Mössbauer Absorption Spectroscopy

et al. 2020

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In Fe-based Fischer-Tropsch Synthesis (FTS), the Fe carbides form under the carburizing H 2 : CO reaction atmosphere providing the active phases for hydrocarbon synthesis. H 2 reduced Fe (À NaÀ S)/α-Al 2 O 3 catalyst materials, with and without NaÀ S promotion, were carburized under CO at 240-440°C to form Fe carbides. X-ray Powder Diffractometry (XRPD) with Rietveld Quantitative Phase Analysis (R-QPA) and Mössbauer Absorption Spectroscopy (MAS) were used to identity and quantify the formed Fe carbide phases. The Fe carbides formed in order of increasing temperature are ɛ-Fe 3 C, η-Fe 2 C, χ-Fe 5 C 2 and θ-Fe 3 C. θ-Fe 7 C 3 and a distorted χ-Fe 5 C 2 phase are formed at 25 bar CO (340°C) from a Fe oxide precursor. Fe carbide formation was unaffected by NaÀ S addition, but it did increase Fe oxidation (� 290°C) and preferred formation of χ-Fe 5 C 2 over θ-Fe 3 C phase (� 390°C). The results unify the often ambiguous Fe carbide identification and nomenclature and specify the role of NaÀ S in the carburization process.

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“…A further decrease in the magnetization is presumably associated with the formation of the antiferromagnetic phase of FeO 1−x . The formation of such nonstoichiometric phases have been reported . For Fe/Q and (FeK)/Q, the magnetization drop at T > 300 °C was accompanied by an increase in the H 2 consumption rate, which also indicates the formation of FeO 1–x phase as a result of the magnetite reduction:

{Fe}_{3} {normalO}_{4} + (1 - x) {normalH}_{2} = {3 FeO}_{1 - x} + (1 - x) {normalH}_{2} O

…”

Section: Resultsmentioning

confidence: 92%

“…As a result, smaller FeC x particles with higher specific surface area are formed . In as‐prepared catalysts, the interaction between an alkali metal and iron oxides strengthens Fe—O bonds thus decreasing iron reducibility . However, the formation of iron carbides is promoted by potassium …”

Section: Introductionmentioning

confidence: 99%

Carbon–Silica Composite as an Effective Support for Iron Fischer–Tropsch Synthesis Catalysts

et al. 2019

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Carbon–silica composite is prepared by the impregnation of silica with aqueous glucose solution followed by drying and calcination in an inert atmosphere. This material is proposed as a support for the potassium‐promoted iron catalysts for Fischer–Tropsch synthesis (FTS). The catalysts are prepared by incipient wetness impregnation. The reducibility of CQ‐supported iron is increased and Hägg carbide is formed in the course of activation in CO/H2 flow at 400 °C for 2 h. Subsequent exposure in FTS conditions results in the significant increase of iron carbide particles, from 3–4 to 20–30 nm, while no such increase is detected for the pure silica as support. The carbon–silica composite support provides a beneficial effect on the catalytic activity of iron in CO hydrogenation as well as the suppression of methane formation and increasing Anderson–Schulz–Flory distribution (ASF) chain growth parameter. The catalysts are characterized by nitrogen adsorption, X‐ray absorption spectroscopy (XPS), transmission electron microscopy (TEM), and in situ magnetic measurements in the course of temperature‐programmed reduction by H2 and synthesis gas.

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Effect of alkalis on iron-based Fischer-Tropsch synthesis catalysts: Alkali-FeOx interaction, reduction, and catalytic performance

Cited by 86 publications

References 42 publications

Fischer–Tropsch: Product Selectivity–The Fingerprint of Synthetic Fuels

Fischer–Tropsch: Product Selectivity–The Fingerprint of Synthetic Fuels

Identification of Iron Carbides in Fe(−Na−S)/α‐Al₂O₃ Fischer‐Tropsch Synthesis Catalysts with X‐ray Powder Diffractometry and Mössbauer Absorption Spectroscopy

Carbon–Silica Composite as an Effective Support for Iron Fischer–Tropsch Synthesis Catalysts

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Effect of alkalis on iron-based Fischer-Tropsch synthesis catalysts: Alkali-FeOx interaction, reduction, and catalytic performance

Cited by 86 publications

References 42 publications

Fischer–Tropsch: Product Selectivity–The Fingerprint of Synthetic Fuels

Fischer–Tropsch: Product Selectivity–The Fingerprint of Synthetic Fuels

Identification of Iron Carbides in Fe(−Na−S)/α‐Al2O3 Fischer‐Tropsch Synthesis Catalysts with X‐ray Powder Diffractometry and Mössbauer Absorption Spectroscopy

Carbon–Silica Composite as an Effective Support for Iron Fischer–Tropsch Synthesis Catalysts

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Identification of Iron Carbides in Fe(−Na−S)/α‐Al₂O₃ Fischer‐Tropsch Synthesis Catalysts with X‐ray Powder Diffractometry and Mössbauer Absorption Spectroscopy