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

Extracts of liquefaction residue from Shenmu-Fugu subbituminous coal (LR_SFSBC) 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 LR_SFSBC was extracted. Aromatic C=C, C=O, and CO were identified in the extracts by FTIR analysis. Nitrogen, oxygen, and sulfur forms of LR_SFSBC 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 LR_SFSBC 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.