A comprehensive study on the transformation of chemical structures in the plastic layers during coking of Australian coals

Yunze Hui, Lu Tian, Soonho Lee, Yixin Chen, Arash Tahmasebi, Merrick Mahoney, Jianglong Yu

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Abstract

The changes in chemical structures over the plastic layer region during the coking of coals have a significant impact on coke formation and coke quality. This paper employed the Solid-state 13Carbon Nuclear Magnetic Resonance (13C NMR), and the Synchrotron attenuated total reflection Fourier transform infrared (ATR-FTIR) microspectroscopy (Synchrotron IR) to study the transformation of the chemical structures in plastic layer samples. The light gases (mainly methane and hydrogen) released from coking process were analyzed using micro gas chromatography (micro-GC) connected to a small coking reactor heated in an electric furnace that simulated the formation of the plastic layers. The results show clearly that the total aromaticity increased consistently in the plastic layers for all coals tested, while the amounts of side-chains decreased significantly during the plastic layer. There was a clear trend showing that the total number of bridge bonds and the looped structures, indicating that the degree of cross-linking would increase through the plastic layer. The plastic layer samples from low fluidity exhibited cross-linking structures with a high degree of branching and aromaticity, while those from high fluidity coals formed cross-linking structures with a relatively low degree of aromaticity and branching but with a large number of bridge bonds and looped structures. The transferable methyl, methylene and hydrogen were strongly correlated to the cross-linking reaction and side-chain elimination in the thermoplastic region, which is reflected by the release profiles of methane and hydrogen gas during the plastic layer stage.

Original languageEnglish
Article number104947
Number of pages10
JournalJournal of Analytical and Applied Pyrolysis
Volume152
DOIs
Publication statusPublished - Nov 2020
Externally publishedYes

Keywords

  • C NMR
  • Coking coal
  • Cross-linking structures
  • Plastic layer
  • Synchrotron IR

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