Comparative Kinetic Analysis of Ethane Pyrolysis at 0.1 and 2.0 MPa

Saldana, Mario H.; Bogin, Gregory E.; Wang, Kun; Dean, Anthony M.

doi:10.1021/acs.energyfuels.6b01752

Cited by 8 publications

(15 citation statements)

References 26 publications

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“…Ethane (C 2 H 6 ) pyrolysis is a fundamental process in the global chemical industry and energy economy. More than 100 million tons of ethylene (C 2 H 4 ) are produced annually by steam cracking of ethane at temperatures exceeding 1000 K [1, 2] . As a major component of natural gas, ethane is also widely used for energy production, and the pyrolytic initiation of its combustion plays a central role here as well [3–6] .…”

Section: Figurementioning

confidence: 99%

“…These growth mechanisms are important sources of carbonaceous species that decrease yields and efficiency in high temperature processes [8, 30] . Moreover, bimolecular reactions of ethyl have been suggested as the cause of the reduced selectivity of ethane cracking at high pressures [1] . Despite the significance of these reactions, they are often modeled using theoretical or estimated rate constants.…”

Section: Figurementioning

confidence: 99%

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Direct Observation of the Ethyl Radical in the Pyrolysis of Ethane

Genossar‐Dan,

Atlas,

Fux

et al. 2023

Angewandte Chemie

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We report the first direct detection of ethyl radical in the pyrolysis of ethane. Observation of this vital intermediate was made possible in this extremely reactive environment by the use of a microreactor coupled with synchrotron radiation and photoelectron photoion coincidence (PEPICO) spectroscopy, despite its short lifetime and low concentration. Together with ab‐initio master equation‐calculated rates and fully coupled computational fluid dynamics simulations, our measurements show that even under the low pressures and short residence times in our experiment, ethyl formation can only be explained by bimolecular reactions; the most important is the catalytic attack of ethane by H atoms, which are then regenerated by decomposition of the nascent ethyl radicals. Our results complete the observation of all hypothesized intermediates in this industrially important process and highlight the need for further studies under additional conditions using similar methods to improve existing models and optimize process chemistries.

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Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Direct Observation of the Ethyl Radical in the Pyrolysis of Ethane

Genossar‐Dan,

Atlas,

Fux

et al. 2023

Angewandte Chemie

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“…From a fundamental point of view, ethane is an important intermediate in the oxidation and pyrolysis of hydrocarbon fuels. 20,21 Therefore, understanding pressure effects on the relaxation, dissociation, oxidation, and pyrolysis of ethane is fundamental for the hierarchical construction of higher hydrocarbon fuel models. Hence, there is recent experimental motivation to study the oxidation and pyrolysis of ethane at high pressure.…”

Section: Introductionmentioning

confidence: 99%

“…First, ethane is a prototypical system for studying the kinetics and dynamics of hydrocarbon combustion in both theory and experiment. From a fundamental point of view, ethane is an important intermediate in the oxidation and pyrolysis of hydrocarbon fuels. , Therefore, understanding pressure effects on the relaxation, dissociation, oxidation, and pyrolysis of ethane is fundamental for the hierarchical construction of higher hydrocarbon fuel models. Hence, there is recent experimental motivation to study the oxidation and pyrolysis of ethane at high pressure. − Pressures ranging from 10 to 987 atm, where argon is normally used to dilute the gas mixtures, have been studied.…”

Section: Introductionmentioning

confidence: 99%

Pressure Effects on the Relaxation of an Excited Ethane Molecule in High-Pressure Bath Gases

et al. 2021

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We use molecular dynamics to calculate the rotational and vibrational energy relaxation of C2H6 in Ar, Kr, and Xe bath gases over a pressure range of 10–400 atm and at temperatures of 300 and 800 K. The C2H6 is instantaneously excited by 80 kcal/mol randomly distributed into both vibrational and rotational modes. The computed relaxation rates show little sensitivity to the identity of the noble gas in the bath. Vibrational relaxation rates show a nonlinear pressure dependence at 300 K. At 800 K the reduced range of bath gas densities covered by the range of pressures does not yet show any nonlinearity in the pressure dependence. Rotational relaxation is characterized with two relaxation rates. The slower rate is comparable to the vibrational relaxation rate. The faster rate has a linear pressure dependence at 300 K but an irregular, nonlinear pressure dependence at 800 K. To understand this, a model was developed based on approximating the periodic box used in the molecular dynamics simulations by an equal-volume collection of cubes where each cube is sized to allow only single occupancy by the noble gas or the molecule. Combinatorial statistics then leads to a pressure- and temperature-dependent analytic distribution of the bath gas species the molecule encounters in a collision. This distribution, the dissociation energy of molecule/bath gas complexes and bath gas clusters, and the computed energy release per collision combine to show that only at 300 K is the energy release sufficient to dissociate likely complexes and clusters. This suggests that persistent and pressure-dependent clusters and complexes at 800 K may be responsible for the nonlinear pressure dependence of rotational relaxation.

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“…Usually, the temperature for manufacturing carbonaceous materials ranges from 1000 to 4000 K, in the cases of arc discharge, CVD, laser ablation, pyrolysis, , and combustion. , The high temperature contributes to the atomic C formation from initial reactants. Thus, the nucleation and growth mechanisms of carbonaceous materials at high temperature can simply be seen as the self-assembly of atomic C. For this, many kinetic models have been developed to describe the pyrolysis of hydrocarbons. − Nevertheless, these models were employed to compare and fit the elementary reactions with experimental observations to determine dominant reactions in the total conversions alone and cannot provide any dynamic detail at the atomic level. Using reactive molecular dynamics (RMD), our recent work indicated that the pyrolysis product of CH 4 is an orderly cavity-like carbonaceous material as a possible precursor of CNTs, while that of acetylene (C 2 H 2 ) is a disorderly C black .…”

Section: Introductionmentioning

confidence: 99%

Higher Activity Leading to Higher Disorder: A Case of Four Light Hydrocarbons to Variable Morphological Carbonaceous Materials by Pyrolysis

Liu

et al. 2018

J. Phys. Chem. C

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The subtle and efficient manufacture of high-quality carbonaceous materials dominates their extensive applications. Meanwhile, revealing the underlying mechanism in the formation of carbonaceous materials is crucial to improving their manufacture efficiency. In the present work, we focus upon the pyrolysis mechanism for four light hydrocarbons including methane, CH4, ethane, C2H6, ethylene, C2H4, and acetylene, C2H2, to carbonaceous materials, combined with reactive molecular dynamics (RMD) simulations. The carbonaceous materials with various morphologies are observed in our simulations, and the morphologies are strongly dependent on the initial reactants; i.e., a disorderly C cluster, a crossed C multilayer, and an orderly C monolayer are made from C2H2, C2H4, and C2H6 and CH4, respectively, as ascertained partly in experiments. Tracing the RMD trajectories, we confirm that the pyrolysis of all four light hydrocarbons undergoes three stages, including the C chain elongation with generation of new small carbonaceous molecules or radicals, the formation and growth of polycyclic aromatic hydrocarbons, and the stable growth of C clusters. The morphologic difference of the final C clusters is attributed to the reactant activity and C growth styles. That is, the higher activity and the faster growth by the C2 addition facilitate the more disorderly arrangement of C atoms, and vice versa. Typically, the dense C2H2 tends to form disorderly C black, while the thin CH4, to orderly C nanotubes. It shows that selecting the reactants in terms of their activities is a key to preparing orderly carbonaceous materials. These findings are expected to be useful to understand the formation mechanism and design techniques for efficiently manufacturing high-quality carbonaceous materials.

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Comparative Kinetic Analysis of Ethane Pyrolysis at 0.1 and 2.0 MPa

Cited by 8 publications

References 26 publications

Direct Observation of the Ethyl Radical in the Pyrolysis of Ethane

Direct Observation of the Ethyl Radical in the Pyrolysis of Ethane

Pressure Effects on the Relaxation of an Excited Ethane Molecule in High-Pressure Bath Gases

Higher Activity Leading to Higher Disorder: A Case of Four Light Hydrocarbons to Variable Morphological Carbonaceous Materials by Pyrolysis

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