Theoretical and Experimental Insight into Coal Structure: Establishing a Chemical Model for Yuzhou Lignite

Wang, Jieping; Li, Guangyue; Guo, Rui; Li, Anqi; Liang, Yinghua

doi:10.1021/acs.energyfuels.6b01854

Cited by 54 publications

(21 citation statements)

References 45 publications

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“…Wang et al [28] used 13 C NMR techniques to analyze the types and existing forms of aromatic structures and aliphatic structures of lignite, combined with elemental analysis, and provided the molecular structure model of lignite. The structural parameters of coal molecules, including the composition and content of functional groups, the aromatic carbon ratio, and the aromatic ring condensation degree, can be quantitatively obtained by 13 C NMR and FTIR techniques.…”

Section: Introductionmentioning

confidence: 99%

Fine Characterization of the Macromolecular Structure of Huainan Coal Using XRD, FTIR, 13C-CP/MAS NMR, SEM, and AFM Techniques

Zhang

et al. 2020

Molecules

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Research on the composition and structure of coal is the most important and complex basic research in the coal chemistry field. Various methods have been used to study the structure of coal from different perspectives. However, due to the complexity of coal and the limitations of research methods, research on the macromolecular structure of coal still lacks systematicness. Huainan coalfield is located in eastern China and is the largest coal production and processing base in the region. In this study, conventional proximate analysis and ultimate analysis, as well as advanced instrumental analysis methods, such as Fourier transform infrared spectroscopy (FITR), X-ray diffraction (XRD), 13C-CP/MAS NMR, and other methods (SEM and AFM), were used to analyze the molecular structure of Huainan coal (HNC) and the distribution characteristics of oxygen in different oxygen-containing functional groups (OCFGs) in an in-depth manner. On the basis of SEM observation, it could be concluded that the high-resolution morphology of HNC’s surface contains pores and fractures of different sizes. The loose arrangement pattern of HNC’s molecular structure could be seen from 3D AFM images. The XRD patterns show that the condensation degree of HNC’s aromatic ring is low, and the orientation degree of carbon network lamellae is poor. The calculated ratio of the diameter of aromatic ring lamellae to their stacking height (La/Lc = 1.05) and the effective stacking number of aromatic nuclei (Nave = 7.3) show that the molecular space structure of HNC is a cube formed of seven stacked aromatic lamellae. The FTIR spectra fitting results reveal that the aliphatic chains in HNC’s molecular structure are mainly methyne and methylene. Oxygen is mainly –O–, followed by –C=O, and contains a small amount of –OH, the ratio of which is about 8:1:2. The molar fraction of binding elements has the approximate molecular structure C100H76O9N of organic matter in HNC. The results of the 13C NMR experiments show that the form of aromatic carbon atoms in HNC’s structure (the average structural size Xb of aromatic nucleus = 0.16) is mainly naphthalene with a condensation degree of 2, and the rest are aromatic rings composed of benzene rings and heteroatoms. In addition, HNC is relatively rich in ≡CH and –CH2– structures.

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Section: Introductionmentioning

confidence: 99%

Fine Characterization of the Macromolecular Structure of Huainan Coal Using XRD, FTIR, 13C-CP/MAS NMR, SEM, and AFM Techniques

Zhang

et al. 2020

Molecules

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“…Zheng et al (2013) investigated the pyrolysis reaction of bituminous coal at 1,000-2000 K (250 ps in duration) based on the Wister and Shinn coal macromolecular representations and highlighted the consistency of the three types of pyrolysis products between MD and experimental results. The comparison of ReaxFF MD and thermogravimetric experimental results could verify the coal macromolecular representation constructed via the elemental analysis, nuclear magnetic resonance (NMR), and infrared spectroscopy (Wang et al, 2017).…”

Section: Coal Pyrolysis and Gas Generationmentioning

confidence: 82%

A Review on the Application of Molecular Dynamics to the Study of Coalbed Methane Geology

et al. 2021

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Over the last three decades, molecular dynamics (MD) has been extensively utilized in the field of coalbed methane geology. These uses include but are not limited to 1) adsorption of gaseous molecules onto coal, 2) diffusion of gaseous molecules into coal, 3) gas adsorption-induced coal matrix swelling and shrinkage, and 4) coal pyrolysis and combustion. With the development of computation power, we are entering a period where MD can be widely used for the above higher level applications. Here, the application of MD for coalbed methane study was reviewed. Combining GCMC (grand canonical Monte Carlo) and MD simulation can provide microscopic understanding of the adsorption of gaseous molecules onto coal. The experimental observations face significant challenges when encountering the nanoscale diffusion process due to coal structure heterogeneity. Today, all types of diffusion coefficients, such as self-, corrected-, and transport-diffusion coefficients can be calculated based on MD and the Peng-Robinson equation. To date, the MD simulation for both pure and multi-components has reached a situation of unprecedented success. Meanwhile, the swelling deformation of coal has been attracting an increasing amount of attention both via experimental and mimetic angles, which can be successfully clarified using MD and a poromechanical model incorporating the geothermal gradient law. With the development of computational power and physical examination level, simulation sophistication and improvements in MD, GCMC, and other numerical models will provide more opportunities to go beyond the current informed approach, gaining researcher confidence in the engagement in the estimation of coal-swelling deformation behaviors. These reactive MD works have clarified the feasibility and capability of the reactive force field ReaxFF to describe initial reactive events for coal pyrolysis and combustion. In future, advancing MD simulation (primarily characterized by the ReaxFF force field) will allow the exploration of the more complex reaction process. The reaction mechanism of pyrolysis and spontaneous combustion should also be a positive trend, as well as the potential of MD for both visualization and microscopic mechanisms for more clean utilization processes of coal. Thus, it is expected that the availability of MD will continue to increase and be added to the extensive list of advanced analytical approaches to explore the multi-scaled behaviors in coalbed methane geology.

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“…Lignite is well known to contain amounts of oxygen, and the basic structure of the coal unit includes the polycondensation of various aromatic rings [ 46 , 47 ], single aromatic ring or heterocyclic rings, and the connected hydroxyl (–OH), carboxyl (–COOH), carbonyl (–C=O), methoxy (–OCH 3 ), as well as metal ions coordinated with oxygen functional group [ 48 ]. These basic structural units were connected by bridge bond to give rise to the macromolecular structure, and the cage type three-dimensional structure was formed by hydrogen bonds [ 49 – 54 ]. Based on the results in this work and the structure of the coal, the possible interaction between K + or Ca 2+ and the carboxyl structure is shown in figure 7 .…”

Section: Resultsmentioning

confidence: 99%

The catalytic effect of calcium and potassium on CO ₂ gasification of Shengli lignite: the role of carboxyl

Ban¹,

Wang²,

Li³

et al. 2018

R. Soc. open sci.

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The CO2 gasification of Chinese Shengli lignite (SL) catalysed by K+ and Ca2+ was studied. The results showed that calcium could greatly decrease the gasification reaction temperature of SL, and the gasification reaction rates of acid-treated SL catalysed by calcium were significantly higher than that catalysed by potassium. Kinetic analysis showed that the activation energy of the reaction catalysed by calcium was much lower than that catalysed by potassium, which was the reason for the higher catalytic activity of calcium. Fourier transform infrared characterization showed that, compared with acid-treated SL, the addition of K+/Ca2+ resulted in the significant weakening of C=O bond, and new peaks attributed to carboxylate species appeared. X-ray photoelectron spectroscopy results indicated that the numbers of C=O decreased after the metal ions were added, indicating the formation of metal–carboxylate complexes. Raman characterization showed that the ID1/IG values increased, suggesting more structural defects, which indicated that the reactivity of coal samples had a close relation with amorphous carbon structures. Ca2+ could interact with the carboxyl structure in lignite by both ionic forces and polycarboxylic coordination, while K+ interacted with carboxyl structure mainly via ionic forces.

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Theoretical and Experimental Insight into Coal Structure: Establishing a Chemical Model for Yuzhou Lignite

Cited by 54 publications

References 45 publications

Fine Characterization of the Macromolecular Structure of Huainan Coal Using XRD, FTIR, 13C-CP/MAS NMR, SEM, and AFM Techniques

Fine Characterization of the Macromolecular Structure of Huainan Coal Using XRD, FTIR, 13C-CP/MAS NMR, SEM, and AFM Techniques

A Review on the Application of Molecular Dynamics to the Study of Coalbed Methane Geology

The catalytic effect of calcium and potassium on CO ₂ gasification of Shengli lignite: the role of carboxyl

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Theoretical and Experimental Insight into Coal Structure: Establishing a Chemical Model for Yuzhou Lignite

Cited by 54 publications

References 45 publications

Fine Characterization of the Macromolecular Structure of Huainan Coal Using XRD, FTIR, 13C-CP/MAS NMR, SEM, and AFM Techniques

Fine Characterization of the Macromolecular Structure of Huainan Coal Using XRD, FTIR, 13C-CP/MAS NMR, SEM, and AFM Techniques

A Review on the Application of Molecular Dynamics to the Study of Coalbed Methane Geology

The catalytic effect of calcium and potassium on CO 2 gasification of Shengli lignite: the role of carboxyl

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The catalytic effect of calcium and potassium on CO ₂ gasification of Shengli lignite: the role of carboxyl