Insight into the chemical complexity of ethanolysis products from extraction residue of Zhaotong lignite

•Each aromatic cluster in ethanolyzed residue (ER) from Zhaotong lignite contains one or two rings on average.•The total yield of soluble portions (E1–E4) from the ER ethanolysis with NaOH is up to 70.7%.•Numerous oxygen-/nitrogen-containing compounds were detected in E1–E4 with FTICRMS.•The most abundant class species in E1–E4 are O2, O2, O3, and O4, respectively.

Ethanolysis of an ethanolyzed residue (ER) from Zhaotong lignite with NaOH was conducted to afford extracts 1–4 (E1–E4). The yields of E1–E4 are 47.1%, 10.6%, 3.0%, and 10.0%, respectively. All the extracts were analyzed with a negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer (ESI FTICRMS). In addition, carbon skeleton structures in the ER were determined using a solid-state 13C nuclear magnetic resonance spectrometer. The results suggest that the carbon types in the ER mainly consist of aliphatic (52.3%) and aromatic (42.0%) carbons. CH3– and –CH2– are the major aliphatic carbons. Each aromatic cluster contains one or two aromatic rings on average. According to analysis with FTICRMS, thousands of compounds were detected in the extracts, mainly being oxygen-containing (Ox, x = 1–8) class species with double bond equivalent (DBE) values of 1–18 and carbon numbers of 7–37. The most abundant class species in E1–E4 are O2, O2, O3, and O4, respectively. E4 contains low relative contents of O2–O3 class species but high relative contents of O4–O6 class species. The identified Ox class species are mainly ascribed to fatty acids, areneols, and arenecarboxylic acids. Furthermore, nitrogen-containing multiheteroatomic (N1Ox and N2Ox, x = 1–8) class species with DBE values of 3–17 and carbon numbers of 13–34 were also identified in the extracts.

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