Molecular identification of nitrogen-containing aromatics for chemical separation from five fractions distilled from a high temperature coal tar

Base soluble portions (BSPs) obtained by acid-base extraction of 5 high-temperature coal tar (HTCT) fractions were comprehensively analyzed with the gas chromatograph/mass spectrometer (GC/MS), Fourier transform infrared (FTIR) spectrometer, and quadrupole exactive orbitrap mass spectrometer (QPEOTMS) equipped with positive-ion atmospheric pressure chemical ionization. The relative content of nitrogen-containing aromatics (NCAs) in each fraction showed a decreasing trend in washing oil (97.5 %) > anthracene oil (95.8 %) > light oil (82.7 %) > naphthalene oil (76.4 %) > phenol oil (12.1 %). Among them, NCAs such as quinoline, acenaphtho[1,2-b]pyridine, benzo[f]quinoline, acridine, benzo[h]quinoline, and anthracene-9-carbonitrile were selectively enriched. The FTIR spectra of BSPs showed significant differences, mainly concentrated in the wavenumbers of 3655, 3520, 3444, 3316, 3051, 1629, 1397, 1131, and 749 cm(-)(1). Semi-quantitative characterization of the BSPs functional group distribution by FTIR spectra basically supports GC/MS analysis. The QPEOTMS analysis shows that NnOxSy (n = 1-4) class species with double bond equivalent (DBE) values of 4-28 and carbon number (CN) at 4-45 are the main basic compounds. N1OxSy species (50.2 %) with DBE = 7 are the most abundant in BSPLO, while the N-1 species with CN = 9 account for 27.2 % in BSPLO. Quinolines with DBE = 7 and CN = 9-11 are the main N-1 species in BSPLO. However, benzoquinolines or anthracene-9-carbonitrile account for a large share in BSPAO. Comprehensive evaluation of various instruments facilitates molecular identification of the detailed composition information of NCAs in HTCT fractions for cleaning and value-added utilization as nitrogen-containing chemicals.