Activation Studies with a Precipitated Iron Catalyst for Fischer-Tropsch Synthesis

Bukur, Dragomir B.; Nowicki, Ł.; Manne, Rajesh Kumar; Lang, Xiaosu

doi:10.1006/jcat.1995.1218

Cited by 160 publications

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“…Metallic iron is identified based on the small sextet with the hyperfine magnetic field (H) of 329 kOe (ref. 8). The formation of e-Fe 2 C is corroborated by three sextets with H values of 142 (Sextet A), 172 (Sextet B) and 235 kOe (Sextet C) 6,36,37 .…”

Section: Resultsmentioning

confidence: 86%

“…During FTS, carbon atoms cleaved from CO show high affinity to iron atoms, so iron catalysts present rich phase chemistry towards the formation of iron carbide(s) 5 . While cementite (y-Fe 3 C) and Hägg carbide (w-Fe 5 C 2 ) are mostly reported in FTS studies, hexagonal iron carbides (e 0 -Fe 2.2 C, e-Fe 2 C) are sporadically identified at comparatively low temperatures and/or low H 2 /CO ratios [6][7][8][9][10][11] . These iron carbides differ from carbon positions in the hexagonally close packed iron lattice.…”

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confidence: 99%

“…It is generally acknowledged that iron carbides, as well as in some reports, metallic iron, are the active phase in FTS 5,10,[13][14][15][16][17][18][19][20] . At typical FTS temperature of 543 K, many reports agree that the active phase is w-Fe 5 C 2 , while y-Fe 3 C is a spectator or a deactivation phase 10,19,[21][22][23] .…”

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confidence: 99%

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ε-Iron carbide as a low-temperature Fischer–Tropsch synthesis catalyst

et al. 2014

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e-Iron carbide has been predicted to be promising for low-temperature Fischer-Tropsch synthesis (LTFTS) targeting liquid fuel production. However, directional carbidation of metallic iron to e-iron carbide is challenging due to kinetic hindrance. Here we show how rapidly quenched skeletal iron featuring nanocrystalline dimensions, low coordination number and an expanded lattice may solve this problem. We find that the carbidation of rapidly quenched skeletal iron occurs readily in situ during LTFTS at 423-473 K, giving an e-iron carbidedominant catalyst that exhibits superior activity to literature iron and cobalt catalysts, and comparable to more expensive noble ruthenium catalyst, coupled with high selectivity to liquid fuels and robustness without the aid of electronic or structural promoters. This finding may permit the development of an advanced energy-efficient and clean fuel-oriented FTS process on the basis of a cost-effective iron catalyst.

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Section: Resultsmentioning

confidence: 86%

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confidence: 99%

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ε-Iron carbide as a low-temperature Fischer–Tropsch synthesis catalyst

et al. 2014

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“…The analysis was completed by fitting the sample diffraction to an appropriate model where the lattice constants, scale factor, peak profile functions, and atomic potentials were varied to produce a simulated diffraction pattern nearly identical to the experimental XRD data. The models were chosen based upon knowledge of synthesis, reaction conditions, and phases previously identified in similar studies, that is, Rh metal, Fe metal, Fe-Rh alloys (FeRh and Fe0.7Rh0.3), FeO, Fe2O3, Fe3C, Fe2C, Fe5C2, anatase TiO2, and rutile TiO2 [20][21][22][23][24][25][26][27][28][29][30][31][32]. A complete refinement provides information about phase quantification, lattice constants, and particle size.…”

Section: In Situ Structure Determinationsmentioning

confidence: 99%

The effect of Fe–Rh alloying on CO hydrogenation to C2+ oxygenates

Palomino

Magee

Llorca³

et al. 2015

Journal of Catalysis

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a b s t r a c t A combination of reactivity and structural studies using X-ray diffraction (XRD), pair distribution function (PDF), and transmission electron microscopy (TEM) was used to identify the active phases of Fe-modified Rh/TiO2 catalysts for the synthesis of ethanol and other C2+ oxygenates from CO hydrogenation. XRD and TEM confirm the existence of Fe-Rh alloys for catalyst with 1-7 wt% Fe and '""2 wt% Rh. Rietveld refinements show that FeRh alloy content increases with Fe loading up to '""4 wt%, beyond which segregation to metallic Fe becomes favored over alloy formation. Catalysts that contain Fe metal after reduction exhibit some carburization as evidenced by the formation of small amounts of Fe3C during CO hydrogenation. Analysis of the total Fe content of the catalysts also suggests the presence of FeOx also increased under reaction conditions. Reactivity studies show that enhancement of ethanol selectivity with Fe loading is accompanied by a significant drop in CO conversion. Comparison of the XRD phase analyses with selectivity suggests that higher ethanol selectivity is correlated with the presence of Fe-Rh alloy phases. Overall, the interface between Fe and Rh serves to enhance the selectivity of ethanol, but suppresses the activity of the catalyst which is attributed to the blocking or modifying of Rh active sites.

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“…Sasol in South Africa. It has been tested extensively at TAMU [1][2][3][4], and was used in previous study of kinetics of Fischer-Tropsch (F-T) synthesis by Lox and Froment [5,6]. It is a robust catalyst and its selectivity is similar to that of TAMU's catalyst.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of Slurry Phase Fischer-Tropsch Synthesis

Bukur¹

2004

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This report covers the second year of this three-year research grant under the University Coal Research program. The overall objective of this project is to develop a comprehensive kinetic model for slurry phase Fischer-Tropsch synthesis on iron catalysts. This model will be validated with experimental data obtained in a stirred tank slurry reactor (STSR) over a wide range of process conditions. The model will be able to predict concentrations of all reactants and major product species (H 2 O, CO 2 , linear 1-and 2-olefins, and linear paraffins) as a function of reaction conditions in the STSR.During the second year of the project we completed the STSR test SB-26203 (275-343 h on stream), which was initiated during the first year of the project, and another STSR test (SB-28603 lasting 341 h). Since the inception of the project we completed 3 STSR tests, and evaluated catalyst under 25 different sets of process conditions. A precipitated iron catalyst obtained from Ruhrchemie AG (Oberhausen-Holten, Germany) was used in all tests. This catalyst was used initially in commercial fixed bed reactors at Sasol in South Africa. Also, during the second year we performed a qualitative analysis of experimental data from all three STSR tests. Effects of process conditions (reaction temperature, pressure, feed composition and gas space velocity) on water-gas-shift (WGS) activity and hydrocarbon product distribution have been determined.

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Activation Studies with a Precipitated Iron Catalyst for Fischer-Tropsch Synthesis

Cited by 160 publications

References 0 publications

ε-Iron carbide as a low-temperature Fischer–Tropsch synthesis catalyst

ε-Iron carbide as a low-temperature Fischer–Tropsch synthesis catalyst

The effect of Fe–Rh alloying on CO hydrogenation to C2+ oxygenates

Kinetics of Slurry Phase Fischer-Tropsch Synthesis

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