DFT study of the chlorine promotion effect on the ethylene adsorption over iron clusters

Pahlavan, Farideh; Pakiari, A.H.

doi:10.1016/j.jmgm.2016.03.009

Cited by 5 publications

(6 citation statements)

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“…The π bonds of C 2 H 4 molecules are broken to form σ bonds as it is chemisorbed to the surface, which is in good agreement with the experimental investigations for the chemisorption of acetylene and C 2 H 4 adsorbed on Fe(110) and (111) surfaces. , Our result is also consistent with a ReaxFF MD simulation by Goddard and co-workers, in which C 2 H 4 chemisorption on the Ni particle surfaces with the π bond break to form σ bond was observed . The C–C bond length of absorbed molecules was calculated to be 1.49–1.62 Å, in agreement with experimental and theoretical values of 1.455–1.52 Å for chemisorption of C 2 H 4 on Fe and Pt clusters. , The calculated C–C bond length in our work is close to that in ethane (1.54 Å), much longer than that of C 2 H 4 (1.35 Å) . It indicates the C–C bond rehybridization from sp 2 to sp 3 .…”

Section: Resultssupporting

confidence: 91%

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Early Events of the Carburization of Fe Nanoparticles in Ethylene Pyrolysis: Reactive Force Field Molecular Dynamics Simulations

2018

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The carburization of transition metals in hydrocarbon pyrolysis is a common corrosion phenomenon in the petrochemical industry. Nevertheless, early events of carburization mechanism remain still unclear. The present work reveals the details at earlier stages of the Fe nanoparticles carburization in ethylene (C2H4) pyrolysis with reactive ReaxFF force field molecular dynamics simulations. Our results show that the chemisorption and dissociation of C2H4 on Fe surfaces are crucial steps to the carburization corrosion. First of all, C2H4 molecules are chemically adsorbed on the surface of the Fe nanoparticle. Afterward, continuous dehydrogenation of C2H4 occurs by C–H bond break to form C2H x (x = 0–3). And finally, an amorphous C-rich carbide FeC3.39 is obtained. The carbide formation proceeds in four sequential and repetitive stages, including chemisorption and dehydrogenation of C2H4 on the surface of the Fe nanoparticle, diffusion and polymerization of C2H x to form short C chains on the surface and in the bulk of the particle, growth and branching of the short chains, and chain cross-linking to form longer and more branched chains. Our finding provides deep insight into the fundamental process of carburization corrosion of Fe nanoparticles in the hydrocarbon pyrolysis, as a common phenomenon observed in practice.

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Section: Resultssupporting

confidence: 91%

“…49−1.62 Å, in agreement with experimental and theoretical values of 1.455− 1.52 Å for chemisorption of C 2 H 4 on Fe46 and Pt clusters 27,47. The calculated C−C bond length in our work is close to that in ethane (1.54 Å), much longer than that of C 2 H 4 (1.35 Å) 48.…”

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confidence: 87%

Early Events of the Carburization of Fe Nanoparticles in Ethylene Pyrolysis: Reactive Force Field Molecular Dynamics Simulations

2018

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“…Small Fe cluster models representing different surface orientations of Fe bcc have been previously used to investigate different adsorption sites of acetylene . In the case of ethylene, computational studies involving small iron clusters have shown that π-orientation is favorable for Fe 2 and Fe 3 while di-σ-orientation provides stronger adsorption for Fe 4 . However, other computations do not indicate this relationship between the cluster size and adsorption configuration .…”

Section: Introductionmentioning

confidence: 99%

Acetylene and Ethylene Adsorption during Floating Fe Catalyst Formation at the Onset of Carbon Nanotube Growth and the Effect of Sulfur Poisoning: a DFT Study

Orbán,

Höltzl

2024

Inorg. Chem.

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Here, we investigated the adsorption of acetylene and ethylene on iron clusters and nanoparticles, which is a crucial aspect in the nascent phase of carbon nanotube growth by floating catalyst chemical vapor deposition (FCCVD). The effect of sulfur on adsorption was also studied due to its indispensable role in the process and its commonly known impact on metal catalyst poisoning. We performed systematic density functional theory (DFT) computations, considering numerous adsorption configurations and iron particles of various sizes (Fe n , n = 3–10, 13, 55). We found that acetylene binds significantly more strongly than ethylene and prefers different adsorption sites. The presence of sulfur decreased the adsorption strength only in the immediate proximity of the adsorbate, suggesting that the effect of sulfur is mainly of steric origin while electronic effects play only a minor role. Higher sulfur coverage of the catalyst surface significantly weakened the binding of acetylene or ethylene. To further investigate this interaction, Bader’s atoms in molecules (AIM) analysis and charge density difference (CDD) were used, which showed electron transfer from iron clusters or nanoparticles to the adsorbate molecules. The charge transfer exhibited a decreasing trend as sulfur coverage increased. These results can also contribute to the understanding of other iron-based catalytic processes involving hydrocarbons and sulfur, such as the Fischer–Tropsch synthesis.

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“…Density functional theory (DFT) calculations are well-suited for modeling gas-phase adsorption on surfaces modeled as 2D periodic slabs, − and they have also been applied to hydrated mineral surfaces interacting with adsorbates. ,− While small cluster models have been used in the past to model adsorption, − here we have opted to use 2D periodic slabs as our surface representative. Using 2D periodic structures to mimic the surface geometry is advantageous because the slabs are more structurally rigid and represent the steric effects of the surface more realistically than small clusters. , However, to fully describe the adsorption processes, it is necessary to include aqueous adsorbate energetics as well as surface–adsorbate bonding.…”

Section: Introductionmentioning

confidence: 99%

Density Functional Theory and Thermodynamics Modeling of Inner-Sphere Oxyanion Adsorption on the Hydroxylated α-Al₂O₃(001) Surface

et al. 2020

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The inner-sphere adsorption of AsO 4 3− , PO 4 3− , and SO 4 2− on the hydroxylated α-Al 2 O 3 (001) surface was modeled with the goal of adapting a density functional theory (DFT) and thermodynamics framework for calculating the adsorption energetics. While DFT is a reliable method for predicting various properties of solids, including crystalline materials comprised of hundreds (or even thousands) of atoms, adding aqueous energetics in heterogeneous systems poses steep challenges for modeling. This is in part due to the fact that environmentally relevant variations in the chemical surroundings cannot be captured atomistically without increasing the system size beyond tractable limits. The DFT + thermodynamics approach to this conundrum is to combine the DFT total energies with tabulated solution-phase data and Nernst-based corrective terms to incorporate experimentally tunable parameters such as concentration. Central to this approach is the design of thermodynamic cycles that partition the overall reaction (here, inner-sphere adsorption proceeding via ligand exchange) into elementary steps that can either be fully calculated or for which tabulated data are available. The ultimate goal is to develop a modeling framework that takes into account subtleties of the substrate (such as adsorption-induced surface relaxation) and energies associated with the aqueous environment such that adsorption at mineral−water interfaces can be reliably predicted, allowing for comparisons in the denticity and protonation state of the adsorbing species. Based on the relative amount of experimental information available for AsO 4 3− , PO 4 3− , and SO 4 2− adsorbates and the well-characterized hydroxylated α-Al 2 O 3 (001) surface, these systems are chosen to form a basis for assessing the model predictions. We discuss how the DFT + thermodynamics results are in line with the experimental information about the oxyanion sorption behavior. Additionally, a vibrational analysis was conducted for the charge-neutral oxyanion complexes and is compared to the available experimental findings to discern the inner-sphere adsorption phonon modes. The DFT + thermodynamics framework used here is readily extendable to other chemical processes at solid−liquid interfaces, and we discuss future directions for modeling surface processes at mineral−water and environmental interfaces.

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DFT study of the chlorine promotion effect on the ethylene adsorption over iron clusters

Cited by 5 publications

References 62 publications

Early Events of the Carburization of Fe Nanoparticles in Ethylene Pyrolysis: Reactive Force Field Molecular Dynamics Simulations

Early Events of the Carburization of Fe Nanoparticles in Ethylene Pyrolysis: Reactive Force Field Molecular Dynamics Simulations

Acetylene and Ethylene Adsorption during Floating Fe Catalyst Formation at the Onset of Carbon Nanotube Growth and the Effect of Sulfur Poisoning: a DFT Study

Density Functional Theory and Thermodynamics Modeling of Inner-Sphere Oxyanion Adsorption on the Hydroxylated α-Al₂O₃(001) Surface

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DFT study of the chlorine promotion effect on the ethylene adsorption over iron clusters

Cited by 5 publications

References 62 publications

Early Events of the Carburization of Fe Nanoparticles in Ethylene Pyrolysis: Reactive Force Field Molecular Dynamics Simulations

Early Events of the Carburization of Fe Nanoparticles in Ethylene Pyrolysis: Reactive Force Field Molecular Dynamics Simulations

Acetylene and Ethylene Adsorption during Floating Fe Catalyst Formation at the Onset of Carbon Nanotube Growth and the Effect of Sulfur Poisoning: a DFT Study

Density Functional Theory and Thermodynamics Modeling of Inner-Sphere Oxyanion Adsorption on the Hydroxylated α-Al2O3(001) Surface

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Density Functional Theory and Thermodynamics Modeling of Inner-Sphere Oxyanion Adsorption on the Hydroxylated α-Al₂O₃(001) Surface