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Xianfeng lignite (XL) was sequentially extracted under ultrasonication at room temperature with petroleum ether, carbon disulfide (CDS), methanol, acetone, and isometric CDS/acetone mixed solvent to afford extracts 1–5, respectively. The mixed solvent-inextractable portion was sequentially extracted with cyclohexane, benzene, 1-methylnaphthalene, methanol, and ethanol at 320 °C to afford extracts 6–10, respectively. The extracts were analyzed with a gas chromatography/mass spectrometer (GC/MS) to characterize biomarkers in XL. The biomarkers were significantly enriched in extracts 1 and 6. They can be classified into a series of n-alkanes, isoprenoid alkanes, terpenoids, n-alkenes, methyl alkanones, n-alkylbenzenes, n-alkyltoluenes, and n-alkyl-p-xylenes. The biomarker distributions provided important information on the main origin of organic matter in XL. Related mechanisms for the formation of biomarkers during coalification were discussed. The residue from sequential thermal extraction was subjected to ruthenium-ion-catalyzed oxidation along with subsequent product analyses with GC/MS and direct analysis in a real-time ionization source coupled to a time-of-flight mass spectrometer (DARTIS/TOFMS) to understand its structural features. The results show that the residue is rich in condensed aromatics (CAs) and methyl is the dominant alkyl side chain on aromatic rings. The aromatic rings in the residue are mainly connected by −(CH2)3– and −CHCH3(CH2)2–. DARTIS/TOFMS analysis suggests that CAs with alkyl-substituted biphenyl and alkyl-substituted phenylbiphenyl skeletons also exist in the residue. This investigation provides an effective approach for understanding biomarkers and the structural features of the macromolecular network in XL.

Geting bituminous coal (GBC) was sequentially extracted with petroleum ether, carbon disulfide (CDS), methanol, acetone, and isometric CDS/acetone mixed solvent at room temperature to afford extracts 1–5 (E1–E5) and residue. Detailed characterizations of the extracts were performed with a gas chromatography/mass spectrometer (GC/MS), Fourier transform infrared (FTIR) spectrometer, and direct analysis in real-time ionization source (DARTIS) coupled to an ion-trap mass spectrometer (ITMS). GBC and its residue were also analyzed with the FTIR spectrometer. Particle sizes of the residue were significantly reduced compared to those of GBC according to the observation with a scanning electron microscope. Arenes with 1–4 rings and more condensed arenes were enriched into E1 and E2, respectively, while more heteroatom-containing organic species were detected in other extracts, especially in E3 and E4 according to GC/MS analysis. The extracts, especially E1–E4, contain more aliphatic moieties and less aromatic moieties compared to GBC and its residue based on FTIR analysis. DARTIS/ITMS proved to be a powerful tool for analyzing thermally labile and/or involatile species, which are difficult to be identified with GC/MS, in the extracts.