Macromolecular transformations for tectonically-deformed high volatile bituminous via HRTEM and XRD analyses

Song, Yu; Jiang, Bo; Li, Ming; Hou, Chenliang; Mathews, Jonathan P.

doi:10.1016/j.fuel.2019.116756

Cited by 45 publications

(41 citation statements)

References 75 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore, as the maturity increases, the size of the aromatic ring increases, which is similar to the maturityresponsive kerogen 39 , 40 and other coal types. 20 , 62 Moreover, this result agrees with the results from the XRD experiment parameter L a . Compared with other coal samples, 21, 63 the five coal samples in this work had a higher frequency of 3 × 3 rings.…”

Section: Discussionsupporting

confidence: 88%

The Chemical and Alignment Structural Properties of Coal: Insights from Raman, Solid-State ¹³C NMR, XRD, and HRTEM Techniques

Zhu

Wang

et al. 2021

ACS Omega

View full text Add to dashboard Cite

The chemical and alignment structures of coal impacts coalbed methane behavior: adsorption, desorption, and diffusion. Recently, the research on accurate characterization techniques for coal structure has received widespread attention. In particular, spatial alignment is critical for the molecular modeling of coal. However, due to the great challenges of quantification, spatial alignment has often been ignored in previous studies. In this study, high-resolution transmission electron microscopy (HRTEM) was employed to quantitatively characterize the fringe length, orientation, and stacking distributions of these five coal samples with different ranks. Raman spectroscopy was utilized to investigate the overall structural disorder of the coal molecules. 13 C nuclear magnetic resonance ( 13 C NMR) was conducted to characterize the chemical structures of coals, and XRD experiments recorded the transition of the microcrystallite structure. The results show that in the range of % R o = 0.39–2.07%, the distributions of the aromatic structural units were similar: mainly composed of fringes of size equivalent to naphthalene and 2 × 2 and 3 × 3 rings. When % R o > 2.07%, the distribution shifted to longer fringes. Moreover, all the samples showed a regional orientation, and when % R o > 2.07%, there was significantly higher alignment. The degree of stacking of fringes were limited, most of which appeared in the form of a single layer. When % R o < 2.07%, the stacking appeared in the form of two or three layers. However, five-layer stacking merely appeared in the sample with % R o = 2.47%. In addition, based on the Raman data, the evolution of carbon disorder was divided into three stages: % R o = 0.39–1.23%, 1.23–2.07%, and 2.07–2.47%, and aromatization caused the overall disorder to decrease. The 13 C NMR data indicated that the chemical structure also transitioned in stages, with aliphatic carbon and oxygen-containing groups gradually decreasing and aromatic carbon increasing. Meanwhile, the XRD data supported increased organization (lower d 002 values) with maturities. Thus, this study provides quantitative information about the spatial alignment and the size of aromatic rings, which helps to improve a comprehensive understanding of the chemical structure of coal and coalbed methane behaviors.

show abstract

Section: Discussionsupporting

confidence: 88%

The Chemical and Alignment Structural Properties of Coal: Insights from Raman, Solid-State ¹³C NMR, XRD, and HRTEM Techniques

Zhu

Wang

et al. 2021

ACS Omega

View full text Add to dashboard Cite

show abstract

“…However, the overall increase in Young's modulus here is 20%, indicating that coal's macromolecular ordering improvement contributed by brittle deformation is relatively limited. This finding corresponds well with the results of Li (2013) and Song et al (2020a).…”

Section: The Impact Of Tectonic Stress On Brittle Tectonically Deform...supporting

confidence: 93%

“…The results showed that strong TDCs exhibit smaller full width at half maximum for the G-peak (fwhm-G) and smaller intensity ratio between the D and G-peaks (I D /I G ), indicating that tectonic deformation can promote the ordering of coal molecular structure. Song et al (2020a) found that compared to brittle deformation, ductile deformation can improve poorly ordered BSU to a more ordered BSU.…”

Section: The Impact Of Tectonic Stress On Brittle Tectonically Deform...mentioning

confidence: 99%

“…Various classification schemes of TDCs have been discussed in the long term (Li 2013;Yao 2017;Song et al, 2020b;Cheng and Pan 2020). Among them, the classification proposed by Ju et al has been widely accepted (Song et al, 2013;Zhang 2014;Yu et al, 2017;Liu and Jiang 2019;Song et al, 2020a;Song et al, 2020b), where TDCs are classified into three series (brittle-, transitional-, ductile series) (Ju et al, 2004). Ju et al's classification scheme is also adopted here.…”

Section: Sample Preparation and Experiments Proceduresmentioning

confidence: 99%

See 1 more Smart Citation

Nanopore Structure and Mechanical Properties in Brittle Tectonically Deformed Coals Explored by Atomic Force Microscopy

2022

View full text Add to dashboard Cite

Tectonically deformed coals (TDCs) are of great importance to coalbed methane exploitation and coal mining safety. Compared to primary coals, reservoir properties of TDCs have been transformed greatly by tectonic stress. Here, the pore structure and mechanical properties of primary coal and brittle TDCs were obtained with atomic force microscopy and software. The results showed that tectonic stress generally promotes pore development and Young’s modulus of brittle TDCs. According to the variation in pore structure and Young’s modulus, two stages were identified: weak brittle deformation stage (primary coal–cataclastic coal–schistose coal–mortar coal) and strong brittle deformation stage (mortar coal–granulitic coal–flaky coal). The extent of tectonic impact varies greatly between these two stages. In weak brittle deformation stage, tectonic stress has little impact on coal pore structure. The mean pore number increases slowly, and the mean pore size decreases slowly. In this stage, half of the pore number increment is provided by macropores of 100–200 nm diameter. In strong brittle deformation stage, tectonic stress has a major impact on coal pore structure. The mean pore number increases quickly, and the mean pore size decreases quickly. Most of the pore number increment comes from mesopores of 10–50 nm diameter and macropores of 50–100 nm diameter. In addition, the Young’s modulus of primary coal and different brittle TDCs varies from 1.5 to 2.0 GPa. In weak brittle deformation stage, the Young’s modulus of different samples levels off. While in strong brittle deformation stage, the Young’s modulus increases gradually. Combined with former studies, it is inferred that tectonic stress can influence coal’s Young’s modulus by transforming its chemical structure.

show abstract

“…CBM is mainly stored in coal’s micropores in the adsorbed state, while a small quantity of free-state CBM exists in pores and fractures. − The spatial arrangement of coal’s complex macromolecular polymers and their combinations is widely investigated using X-ray diffraction, − high-resolution transmission electron microscopy (HRTEM), − Raman spectroscopy, numerical simulation, and so forth. HRTEM plays an important role in macromolecular structure studies, providing fringe images and allowing one to directly obtain macromolecular structural parameters .…”

Section: Introductionmentioning

confidence: 99%

Effect of the Coal Molecular Structure on the Micropore Volume and the Coalbed Methane Content

Wang

Yang

et al. 2021

Energy Fuels

View full text Add to dashboard Cite

Coal mainly consists of complex organic macromolecular polymers. Their spatial arrangement and macromolecular structural parameters control the coal reservoir property. This study evaluated the effects of coal’s macromolecular structural evolution on the micropores and established the relation between the coal heterogeneity and the coalbed methane content in the vertical direction. Five groups of samples with a reflectivity range of 0.60–1.01% and a burial depth range of 400–1200 m were collected from the Fukang mining area, Xinjiang, China. Variations of coal’s macromolecular structural parameters, namely, the preferential development direction, fringe length, fringe separation, and fringe tortuosity, with the burial depth were experimentally determined via high-resolution transmission electron microscopy. As the burial depth increased, coal’s mean fringe length increased and the fringe separation dropped linearly, while the fringe tortuosity gradually decreased at a burial depth of approximately 800 m. In terms of the aromatic ring species, with an increase in the burial depth, the share of aromatic fringes below 2 × 2 dropped while that of aromatic fringes above 3 × 3 increased steadily. The increase in aromatic fringes above 3 × 3 was not conducive to the development of micropores. In addition, the mean fringe separation in the research area decreased linearly with the buried depth, and it decreased by 0.00295 nm per 100 m at the buried depth of 400–1200 m. The reduction in aromatic fringe spacing further reduces the intermolecular pores volume, which is illustrated in low-pressure CO2 measurements. At a burial depth exceeding 1000 m, the content of adsorbed-state methane in the reservoir dropped. Both the fringe separation and the tortuosity degree influenced the Langmuir volume and pressure parameters. The Langmuir pressure dropped with increasing fringe separation. However, it decreased rapidly at first and then slowly with increasing tortuosity degree of the aromatic fringes.

show abstract

Macromolecular transformations for tectonically-deformed high volatile bituminous via HRTEM and XRD analyses

Cited by 45 publications

References 75 publications

The Chemical and Alignment Structural Properties of Coal: Insights from Raman, Solid-State ¹³C NMR, XRD, and HRTEM Techniques

The Chemical and Alignment Structural Properties of Coal: Insights from Raman, Solid-State ¹³C NMR, XRD, and HRTEM Techniques

Nanopore Structure and Mechanical Properties in Brittle Tectonically Deformed Coals Explored by Atomic Force Microscopy

Effect of the Coal Molecular Structure on the Micropore Volume and the Coalbed Methane Content

Contact Info

Product

Resources

About

Macromolecular transformations for tectonically-deformed high volatile bituminous via HRTEM and XRD analyses

Cited by 45 publications

References 75 publications

The Chemical and Alignment Structural Properties of Coal: Insights from Raman, Solid-State 13C NMR, XRD, and HRTEM Techniques

The Chemical and Alignment Structural Properties of Coal: Insights from Raman, Solid-State 13C NMR, XRD, and HRTEM Techniques

Nanopore Structure and Mechanical Properties in Brittle Tectonically Deformed Coals Explored by Atomic Force Microscopy

Effect of the Coal Molecular Structure on the Micropore Volume and the Coalbed Methane Content

Contact Info

Product

Resources

About

The Chemical and Alignment Structural Properties of Coal: Insights from Raman, Solid-State ¹³C NMR, XRD, and HRTEM Techniques

The Chemical and Alignment Structural Properties of Coal: Insights from Raman, Solid-State ¹³C NMR, XRD, and HRTEM Techniques