SOLID STATE<sup>13</sup>C NMR STUDY OF CHINESE COALS

Zhang, Pengzhou; Li, Liyun; Ye, Chaohui

doi:10.1080/08843759508947690

Cited by 5 publications

(5 citation statements)

References 11 publications

(1 reference statement)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This parameter was especially important because it can calculate the size of the aromatic clusters in the coal. 33 , 34 …”

Section: Resultsmentioning

confidence: 99%

“…The peak fitting results of 13 C-NMR spectrum of the Buertai coal can also be used to calculate the ratio of aromatic bridge carbon to the surrounding carbon ( X BP ), X BP = f a B /( f a H + f a P + f a S ) = 0.23. This parameter was especially important because it can calculate the size of the aromatic clusters in the coal. , …”

Section: Resultsmentioning

confidence: 99%

“…This parameter was especially important because it can calculate the size of the aromatic clusters in the coal. 33,34 HRTEM can be used to observe the samples, even fine atomic structures. The original image produced by the electron microscope was black and white (Figure 3a).…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Construction of Buertai Coal Macromolecular Model and GCMC Simulation of Methane Adsorption in Micropores

et al. 2021

View full text Add to dashboard Cite

With the increase in high gas mines in the low coal rank mining area in the northwestern part of China, high gas mines in the low-rank coal mining area have caused many gas emission accidents. Coal is a porous material, containing a large number of micropores (<2 nm), which can absorb large amounts of methane, so it is necessary to explore methane adsorption in micropores of low-rank coal. In this work, FTIR, HRTEM, and 13 C-NMR were used to test the macromolecular structural parameters of Buertai coal, which was a kind of low-rank Jurassic coal in northwestern China. The results showed that the aromatic structural units in the Buertai coal structure mainly consist of naphthalene, anthracene, and phenanthrene. The fat structure mainly occurs in the form of aliphatic side chains, cycloalkanes, and other compounds. The oxygen atoms are present in the form of carbonyl groups, ether bonds, and phenol groups with a ratio of about 6:4:9. The nitrogen atoms are present in the form of pyrrole and pyridine compounds. Finally, the macromolecular structure model of Buertai coal was built, and the calculated NMR spectrum from the model was very consistent with the experimental NMR spectrum of Buertai coal. The relationship between the macromolecular density and energy of Buertai coal was explored using the Amorphous Cell module in the simulation software, Materials Studios 8.0 (MS 8.0), and the density value at the lowest energy was determined to be about 1.23 g/cm 3 . The pore structure parameters of Buertai coal were also calculated. It was found that both pore volume and void fraction decreased evenly as the diameter of the probe molecule increased, but the surface area decreased rapidly when the diameter of the probe molecule was 3.46 Å. All pore sizes were found to be smaller than 10 Å from the pore size distribution (PSD) curve of Buertai coal, which provided a lot of adsorption sites for methane (CH 4 ). The results of the CH 4 adsorption simulation from Grand Canonical Monte Carlo (GCMC) showed that CH 4 is adsorbed inside the micropores of coal, and the adsorption capacity of CH 4 depends on the diameters of micropores when the micropores are less than 8.5 Å. There are many micropores where CH 4 did not appear because these micropores are closed and did not provide a channel for CH 4 to enter. The results of experimental methane adsorption indicate that the excess adsorption capacity from the GCMC simulation was very close to the experimental results of Buertai coal. This work provides a new perspective to study the methane adsorption behavior in micropores of coal.

show abstract

“…This parameter was especially important because it can calculate the size of the aromatic clusters in the coal. 33 , 34 …”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Construction of Buertai Coal Macromolecular Model and GCMC Simulation of Methane Adsorption in Micropores

et al. 2021

View full text Add to dashboard Cite

show abstract

“…Some of these data were used by Genetti et al 32 to fit chemical structure parameters for the CPD model. The data come from the following sources: Genetti et al, 32 Solum et al, 33 Hambly, 34 Perry et al, 29,36 Fletcher and Hardesty, 1 Watt, 3 Gerschel and Schmidt, 45 Cui et al, 46 Ahmed et al, 47 Lin et al, 48 Suggate and Dickinson, 49 and Zhang et al 50 These sources were chosen for their use of the corrected aromaticity f a ′.…”

Section: Approachmentioning

confidence: 99%

Correlations of the Elemental Compositions of Primary Coal Tar and Char

2019

View full text Add to dashboard Cite

Simulations of large-scale coal combustors rely on accurate submodels to describe the chemical and physical changes in coal during reaction. Typically, simplified empirical submodels are tuned to experimental data to reduce the computational complexity. When data are not readily available, simplifying assumptions are used, which can create inaccuracies and biases in a large simulation. One such simplifying assumption in coal research is how to describe the elemental composition of primary pyrolysis products. This paper explores several different empirical model forms to predict the dry, ash-free fractions of C, H, O, N, and S in both the char and tar, using variables such as parent coal composition, reaction conditions (temperatures and particle residence times), and key coal structural parameters derived from NMR measurements to improve the treatment of coal chemistry in large simulations. These model forms were correlated to existing data using a wide range of experimental data using a cross-validation procedure. Since coal structural values can be expensive to measure, several correlations from the literature were used to estimate these values on the basis of information from the proximate and ultimate analyses of the parent coal, including a new correlation for the coal aromaticity. These model forms were tested against a set of measured elemental compositions of tar and char to find the best fit to use in the cross-validation process. The best empirical models are presented that predict the elemental composition of the coal char and tar after devolatilization.

show abstract

“…The most representative structural parameters were first proposed by Solum et al, and most studies in subsequent decades have continued or extended their methods. One of the most important parameters, aromaticity ( f a ), is a good measurement for evaluating the carbon maturity among different coal ranks. , Carbon structures derived from 13 C NMR facilitate the development of modeling methods for coal molecules and their conversion behaviors, such as chemical percolation devolatilization (CPD) , and FLASHCHAIN − pyrolysis models. Moreover, the solid-state CP/MAS 13 C NMR spectroscopy has also been widely applied to analyze the carbon structure of coal-based products during liquefaction and hydrothermal processes, − which can not only indicate the reaction mechanism but also develop models and correlations to predict conversion results.…”

Section: Introductionmentioning

confidence: 99%

Carbon Structure of Coal from the CP/MAS ¹³C NMR Spectra: Effect of Contact Time and Potential Quantitative Modification

Lv,

Fang,

Zeng

et al. 2024

Energy Fuels

View full text Add to dashboard Cite

Carbon structures are important for converting coal into chemical products and carbon materials. Solid-state 13 C nuclear magnetic resonance (NMR) spectroscopy is a powerful approach for determining the structural characteristics of carbon in coal. However, there is much controversy regarding the quantitative reliability of typical cross-polarization magic angle spinning (CP/MAS) 13 C NMR experiments of coal. This study systematically investigated the effect of one of the important factors, CP contact time, using six different coal types with V daf values ranging from 6% to 44%. A series of experimental results at variable contact times from 0.01 to 10 ms indicated that aromatic and aliphatic carbons undergo polarization transfer at different rates, and the nonprotonated carbon of aromatic groups polarized 2−3 times more slowly than that of aliphatic groups. It is challenging for a single CP/MAS 13 C NMR experiment with coal to ensure that each type of carbon is sufficiently polarized before the signal decay of the proton spin−lattice relaxation. As a potential quantitative indicator, the initial magnetization intensity independent of contact time was obtained using a classical five-parameter model for CP dynamics, and the initial aromaticity was further calculated. A linear correlation between the apparent and initial aromaticity was introduced into a calibration method of model compounds to refine the effect of contact time. The modified carbon structural parameters of the coal samples showed better agreement in terms of the H/C atomic ratio, Fourier transform infrared spectroscopy, and empirical aromaticity formulas. These results will help to provide a convenient reference for the quantitative analysis of the carbon structure in coal.

show abstract

SOLID STATE¹³C NMR STUDY OF CHINESE COALS

Cited by 5 publications

References 11 publications

Construction of Buertai Coal Macromolecular Model and GCMC Simulation of Methane Adsorption in Micropores

Construction of Buertai Coal Macromolecular Model and GCMC Simulation of Methane Adsorption in Micropores

Correlations of the Elemental Compositions of Primary Coal Tar and Char

Carbon Structure of Coal from the CP/MAS ¹³C NMR Spectra: Effect of Contact Time and Potential Quantitative Modification

Contact Info

Product

Resources

About

SOLID STATE13C NMR STUDY OF CHINESE COALS

Cited by 5 publications

References 11 publications

Construction of Buertai Coal Macromolecular Model and GCMC Simulation of Methane Adsorption in Micropores

Construction of Buertai Coal Macromolecular Model and GCMC Simulation of Methane Adsorption in Micropores

Correlations of the Elemental Compositions of Primary Coal Tar and Char

Carbon Structure of Coal from the CP/MAS 13C NMR Spectra: Effect of Contact Time and Potential Quantitative Modification

Contact Info

Product

Resources

About

SOLID STATE¹³C NMR STUDY OF CHINESE COALS

Carbon Structure of Coal from the CP/MAS ¹³C NMR Spectra: Effect of Contact Time and Potential Quantitative Modification