Molecular Structure and Electronic Properties of Oil Shale Kerogen: An Experimental and Molecular Modeling Study

Pan, Shuo; Wang, Qing; Bai, Jingru; Chi, Mingshu; Cui, Da; Wang, Zhichao; Qi, Lei; Xu, Fang

doi:10.1021/acs.energyfuels.8b03307

Cited by 40 publications

(33 citation statements)

References 38 publications

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“…114−116 Figure 3 shows some representative kerogen molecular models proposed by these literatures. 104,106,108,119 In order to distinguish the different kerogen types, a Van Krevelen diagram 134 is introduced and the aforementioned kerogen models are plotted in the diagram, as shown in Figure 4. Commonly, the kerogen can be separated into three types, depending on the hydrogen-to-carbon (H/C) and oxygen-tocarbon (O/C) elemental ratios.…”

Section: Molecular Dynamics (Md) Simulationsmentioning

confidence: 99%

Transport of Shale Gas in Microporous/Nanoporous Media: Molecular to Pore-Scale Simulations

Fan

et al. 2020

Energy Fuels

125

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As the typical unconventional reservoir, shale gas is believed to be the most promising alternative for the conventional resources in future energy patterns, attracting more and more attention throughout the world. Generally, the majority of shale gas is trapped within the tight shale rock with ultralow porosity (<10%) and ultrasmall pore size (as less as several nanometers). Thus, the accurate understanding of gas transport characteristic and its underlying mechanism through these microporous/nanoporous media is critical for the effective exploitation of shale reservoir. In this context, we present a comprehensive review on the current advances of multiscale transport simulations of shale gas in microporous/nanoporous media from molecular to pore-scale. For the gas transport in shale nanopores using molecular dynamics (MD) simulations, the structure and force parameters of various nanopore models, including organic models (graphene, carbon nanotubes, and kerogen) and inorganic models (clays, carbonate, and quartz), and flow simulation strategies (such as nonequilibrium molecular dynamics (NEMD) and Grand Canonical Monte Carlo simulations) are systematically introduced and clarified. The significant MD simulation results about gas transport characteristic in shale nanopores then are elaborated respectively for different factors, including pore size, ambient pressure, nanopore type, atomistic roughness, and pore structure, as well as multicomponent. Besides, the two-phase transport characteristic of gas and water is also discussed, considering the ubiquity of water in shale formation. For the lattice Boltzmann method (LBM) and pore network model (PNM) approaches to conduct pore-scale simulations, we briefly review its origins, modifications, and applications for gas transport simulations in a microporous/nanoporous shale matrix. Particularly, the upscaling methods to incorporate MD simulation into LBM and PNM frameworks are emphatically expounded in the light of recent attempts of MD-based pore-scale simulations. It is hoped that this Review would be helpful for the readers to build a systematical overview on the transport characteristic of shale gas in microporous/nanoporous media and subsequently accelerate the development of the shale industry.

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Section: Molecular Dynamics (Md) Simulationsmentioning

confidence: 99%

Transport of Shale Gas in Microporous/Nanoporous Media: Molecular to Pore-Scale Simulations

Fan

et al. 2020

Energy Fuels

125

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“…This result is consistent with those reported in our previous study in that oxygen atoms exhibit a higher electron density compared with that of other atoms in kerogen. 60 Notably, the MEP of the benzene ring structure (black circle areas in Figure 10 ) revealed a clear and uniform distribution due to the effect of conjugated π bonds, indicating that the benzene ring structure is relatively stable and that the functional groups attached to the benzene structure are more likely to be reaction sites. This similar feature is also reflected in the result of Mayer bond-order analysis ( Table 8 ), where the bond-order values of aromatic(C)–aromatic(C) are greater than those of alkane(C)–aromatic(C) in the kerogen model.…”

Section: Resultsmentioning

confidence: 99%

Experimental and Molecular Simulation Studies of Huadian Oil Shale Kerogen

et al. 2022

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Microscopic details on the intrinsic chemical reactivity of Huadian oil shale kerogen associated with electron properties of kerogen were investigated by the combination of experimental analyses and molecular simulations. Multimolecular structure models of kerogen with different densities were constructed for examining the accuracy of the proposed kerogen model. Results revealed that the simulated density of the kerogen model is in good agreement with the experimental value. Evaluation of the kerogen model revealed that the energy optimization process is mainly related to the change in the bond angle caused by atom displacement. According to the results from the Hirshfeld analysis of atomic charges, the S atoms in thiophene and S=O structures exhibit positive charges. By contrast, the concentration of electrons on the S atom led to the electronegativity of the sulfhydryl group. To investigate the distribution characteristics of electrons in kerogen, the molecular electrostatic potential (MEP) of a complete kerogen molecule was calculated. Notably, this is the first report of an MEP diagram of the kerogen model that can provide valuable information on the determination of electrophilic or nucleophilic reaction sites for kerogen.

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“…The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) are the key to determining the chemical reactions of a molecular system. , The electrons in the frontier orbitals (HOMO and LUMO) are usually more active. Therefore, the molecular orbitals of HOMO and LUMO for the three molecular models were calculated using quantum chemistry methods to evaluate the chemical reaction activity of three thermally altered coal molecules, as shown in Figure .…”

Section: Resultsmentioning

confidence: 99%

“…Fortunately, with advances in computer simulation technology, quantum chemistry calculations can provide a series of effective solutions for exploring the reactivity and reactive sites of coal, thereby better explaining and predicting the chemical behaviors and properties of coal and kerogen under complex conditions. − This method has been successfully applied to explore the chemical behaviors and reaction activity of liquefaction and pyrolysis. Feng et al analyzed the hydroliquefaction activity differences of six macerals using quantum chemistry calculations .…”

Section: Introductionmentioning

confidence: 99%

Molecular Modeling and Reactivity of Thermally Altered Coals by Molecular Simulation Techniques

et al. 2021

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In this study, the chemical structure characteristics and reactivity features of three thermally altered coals with different ranks were analyzed by combining molecular modeling and molecular simulation methods to reveal and predict their chemical behaviors and properties. First, 2D molecular models of the three thermally altered coals were constructed based on X-ray photoelectron spectroscopy (XPS), solid-state 13 C nuclear magnetic resonance spectroscopy ( 13 C NMR), high-resolution transmission electron microscopy (HRTEM), and ultimate analysis data. 2D molecular models of the three thermally altered coals show different structural characteristics. 3D molecular models of the three thermally altered coals and their potential energy distributions were obtained by geometry optimization and anneal dynamics simulations. For exploring the reactivity of the three thermally altered coals with different ranks, the frontier molecular orbitals and Mulliken bond orders of the three molecular models were calculated based on quantum chemistry calculations. The frontier orbital (HOMO and LUMO) analysis results indicated that compared with the other two thermally altered coals, the thermally altered coal with R o of 8.32% had higher reactivity in electrophilic or nucleophilic reactions. The bond order results provided detailed information on the active sites of the three thermally altered coal molecules, thereby predicting the thermal behaviors of the three thermally altered coals. These works can provide a theoretical basis for the industrial utilization of thermally altered coal. Meanwhile, these three models will be used in the future to study the combustion, pyrolysis, and graphitization mechanisms of thermally altered coals by reactive molecular dynamics methods.

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Molecular Structure and Electronic Properties of Oil Shale Kerogen: An Experimental and Molecular Modeling Study

Cited by 40 publications

References 38 publications

Transport of Shale Gas in Microporous/Nanoporous Media: Molecular to Pore-Scale Simulations

Transport of Shale Gas in Microporous/Nanoporous Media: Molecular to Pore-Scale Simulations

Experimental and Molecular Simulation Studies of Huadian Oil Shale Kerogen

Molecular Modeling and Reactivity of Thermally Altered Coals by Molecular Simulation Techniques

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