Embedded characteristics and macromolecular structure of sporinite of Pingdingshan coal in Early Permian

ABSTRACT

The sporinite of Pingdingshan coal in Early Permian was mainly microsporinite with less macrosporinite. The aggregated sporinite was scattered in the desmocollinite; the dispersed sporinite was mostly oriented and embedded in the desmocollinite adjacent to the macerals of vitrodetrinite, inertodetrinite, liptodetrinite, etc. To explore the macromolecular structure of sporinite in Pingdingshan coal, the equal density gradient method was chosen to enrich sporinite with the density gradient being primarily 1.16–1.20 g/cm³. The spectral parameters of sporinite were analyzed by FTIR, NMR, XPS, etc. Results indicated that the sporinite had an aliphatic-aromatic structure and it was mostly composed of aliphatics with less aromatics and medium content of C = O oxygen-containing functional group. Each fragrant cluster in sporinite had an average of 1-2 aromatic rings, and the structure of the aromatic carbon was mainly types of naphthalene and benzene. The sporinite contained mostly oxygen atom in the form of phenolic hydroxyl oxygen, carboxyl oxygen, and ether oxygen, of which phenolic hydroxyl oxygen and carboxyl oxygen were the most prominent. In addition, nitrogen atom existed mostly in the form of pyridine. The structural model of the sporinite was constructed and optimized by Materials Studio. The macromolecular structure model of sporinite in Pingdingshan coal had a molecular formula of C₂₀₃H₂₄₄N₂O₃₀ and a relative molecular weight of 3192.10. The corresponding density of the predictive model in the minimum potential energy is 1.19 g/cm³, and the results are consistent with the experimental values. The results are helpful to understand the macromolecular characteristics of sporinite and will provide the theoretical basis for the classification and fine utilization of Pingdingshan coal.

KEYWORDS:

• Pingdingshan coal
• sporinite
• embedded characteristics
• spectral parameters
• structure model

Acknowledgments

Thank you to Professor Zeng Fangui and Xiang Jianhua, School of Mining Engineering, Taiyuan University of Technology, for providing software (ACD/¹³C NMR) in structural model construction.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [41672154].