Characterization of basic heteroatom-containing organic compounds in liquefaction residue from Shenmu–Fugu subbituminous coal by positive-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

•N-, O-, and S-containing species in LRSFSBC were characterized by XPS and ESI FT-ICR MS.•Among the species, the N1 and N1O1 classes are the most abundant.•Molecular structures of N1, N2, N1O1, N1O2, N2S2, and N2O5S1 classes were proposed.•Capsule structures could be present in LRSFSBC.

Extracts of liquefaction residue from Shenmu–Fugu subbituminous coal (LRSFSBC) were obtained by sequential extraction with petroleum ether, methanol, and carbon disulfide. They were analyzed using a Fourier transform infrared (FTIR) spectrometer and a positive-ion (PI) electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer (ESI FT-ICR MS). In total, 65.37% of LRSFSBC was extracted. Aromatic C=C, C=O, and CO were identified in the extracts by FTIR analysis. Nitrogen, oxygen, and sulfur forms of LRSFSBC and the inextractable portion were characterized using X-ray photoelectron spectrometry. A series of basic N1, N2, N1O1, N1O2, N2S2, and N2O5S1 class species were identified in the extracts using ESI FT-ICR MS in PI mode. The ring plus double bond equivalents of the extracts ranges from 1–47, but is mainly below 23. In LRSFSBC some compounds are enwrapped into “capsules”, which are formed from different species associated with each other by hydrogen bonds, π–π interaction, and/or π–hydrogen bonds.