Ethanol Synthesis from Syngas on Transition Metal-Doped Rh(111) Surfaces: A Density Functional Kinetic Monte Carlo Study

Liu, Yang; Liu, Ping

doi:10.1007/s11244-013-0168-1

Cited by 35 publications

(35 citation statements)

References 56 publications

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“…The latter could be explained by core-shell particles with Fe-Rh alloys in the near surface region and internal cores of metallic Rh. This is consistent with the theoretical work by Yang and Liu where Fe was expected to segregate to the surface of Rh and the EXAFS study of Ichikawa and Fukishima where the majority of Fe exists in the oxide phase at the interface between Rh and the support, while Fe 0 exist on the surface of the Rh nanoparticles [7,15]. Fig.…”

Section: Catalyst Structure Under Reaction Conditions: In Situ Xrd Ansupporting

confidence: 92%

“…The latter reaction leads to ethanol after subsequent hydrogenation steps. According to the calculations, Fe addition lowers the barrier to the CO insertion step and thereby increases selectivity of ethanol relative to methane [7]. Our conclusion that a surface Fe-Rh alloy contributes to the improved ethanol selectivity is consistent with the main findings of these calculations, which were based on Fe-doped Rh surfaces with both metals participating.…”

Section: Catalyst Structure Under Reaction Conditions: In Situ Xrd Ansupporting

confidence: 88%

“…Due to the intimate Fe-Rh contact in the alloy fractions, the Fe is likely altering both the number and nature of active Rh sites, which allows ethanol synthesis to compete with methane formation. Density functional theory (DFT) calculations and kinetic Monte Carlo (KMC) simulations suggest that the key factors determining the selectivity of Fe-doped Rh surfaces for ethanol formation are the relative barriers for methyl hydrogenation, [7,12]. The latter reaction leads to ethanol after subsequent hydrogenation steps.…”

Section: Catalyst Structure Under Reaction Conditions: In Situ Xrd Anmentioning

confidence: 99%

“…The need to develop alternative sources of liquid fuels has led to renewed interest in developing catalysts for the efficient conversion of synthesis or ''syn'' gas (CO + H2), derived from biomass, coal, and natural gas, to simple alcohols and higher oxygenates [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Currently, the only industrially applied process involves syngas conversion to methanol over a Cu-based catalyst (CuZnO/Al2O3) at temperatures above 500 K [1].…”

Section: Introductionmentioning

confidence: 99%

“…Studies have shown that Fe loading up to 10 wt% has increased ethanol production while suppressing methane formation for Fe-promoted Rh/Al2O3 [6]. Metal dopants such as Fe are thought to improve performance by increasing the barrier for methane formation and/or decreasing the barrier for CO insertion [7]. Selectivity studies performed by Haider et al, also show that both unpromoted and Fe-promoted Rh catalysts exhibit enhanced activity and selectivity for oxygenates when the support is changed from silica to titania [4].…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

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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Section: Catalyst Structure Under Reaction Conditions: In Situ Xrd Ansupporting

confidence: 92%

Section: Catalyst Structure Under Reaction Conditions: In Situ Xrd Ansupporting

confidence: 88%

Section: Catalyst Structure Under Reaction Conditions: In Situ Xrd Anmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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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Constrained Chemical Dynamics of CO Dissociation/Hydrogenation on Rh Surfaces

Kraus

Frank

2018

Chemistry A European J

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Among noble metal catalysts, rhodium (Rh) is unique in its ability to perform a one-step synthesis of ethanol from syngas. The first steps following the adsorption of syngas on Rh surfaces are assumed to be responsible for the conversion of CO and the selectivity effects between C , C , and oxygenated species. In the current work, constrained ab initio molecular dynamics are applied to investigate the kinetics of CO dissociation and hydrogenation over flat and stepped Rh surfaces. The obtained barriers for the Rh(111) surface are in good agreement with the literature data. On the stepped Rh(211) surface, a large site-dependent variation in barrier height is shown, with the upper terrace exhibiting behavior comparable to the Rh(111) surface, whereas the barriers over the lower terrace site are generally significantly lower. The rate constants are calculated using transition state theory for both surfaces, and are applied successfully in a microkinetic model, confirming the predicted impact on CO conversion and CH /C -oxygenate/C H selectivity. In addition to the high-accuracy energetics and rate constants reported for CO dissociation/hydrogenation and the presentation of an updated microkinetic mechanism for Rh catalysts, the applicability of constrained molecular dynamics for reaction barrier calculation is confirmed, and sensitive pathways affecting the selectivity between formaldehyde/methanol over Rh catalysts are highlighted.

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Catalytic Efficiency in Metallic Nanoparticles: A Computational Approach

Barron

2017

Metal Nanoparticles and Clusters

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Ethanol Synthesis from Syngas on Transition Metal-Doped Rh(111) Surfaces: A Density Functional Kinetic Monte Carlo Study

Cited by 35 publications

References 56 publications

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

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

Constrained Chemical Dynamics of CO Dissociation/Hydrogenation on Rh Surfaces

Catalytic Efficiency in Metallic Nanoparticles: A Computational Approach

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