The broad boiling range, complex composition, and substantial overlap among coal-tar fractions pose significant challenges to their targeted utilization. In this study, an industrial low- and medium-temperature coal tar from Shenmu, China, was separated into 33 narrow-cut fractions by true-boiling-point (TBP) distillation. Simulated distillation, elemental analysis, gas chromatography-mass spectrometry (GC-MS), Fourier transform infrared spectroscopy (FTIR), and two-dimensional correlation infrared spectroscopy (2D-COS) were employed to investigate the boiling-range distribution, molecular composition, and functional-group evolution. The IBP-180 °C fraction accounted for only 1.93%, whereas the 180-240 °C and 240-360 °C fractions accounted for 12.40% and 31.11%, respectively, and fractions above 360 °C accounted for 54.56%, indicating a pronounced medium-to-heavy character. Simulated distillation showed that the equivalent carbon-number distributions shifted toward higher carbon numbers with increasing boiling point, while overlap remained between adjacent fractions, indicating co-distillation among compounds with different carbon numbers and structures. GC-MS analysis revealed that the <110 °C fraction was dominated by monocyclic aromatics and alkanes, with relative abundances of 35.80% and 25.49%, respectively. Phenolic compounds were enriched in the 180-240 °C range; cresols dominated the 180-210 °C fractions, and p-cresol reached an abundance of 68.28% in the 190-200 °C fraction. In the 240-300 °C range, phenolic compounds decreased, whereas naphthalene derivatives and polycyclic aromatic hydrocarbons (PAHs) increased. Higher-boiling and more condensed aromatic components became enriched in the 300-360 °C range, while fractions above 360 °C exhibited increasingly polycyclic and condensed structures. The H/C atomic ratio decreased with increasing boiling point, whereas the O/C atomic ratio increased in the phenol-rich region and then declined, consistent with increasing aromaticity and structural condensation. FTIR and 2D-COS analyses revealed the evolution of functional-group structures. Oxygen-containing functional groups were more pronounced below 230 °C; in the 230-360 °C range, correlations associated with aromatic C=C structures strengthened, and synchronous and asynchronous cross-peaks increased in the 700-900 cm^-1 region, indicating increasingly complex aromatic substitution patterns. Fractions in the 360-500 °C range were dominated by highly condensed aromatic structures, while signals associated with polar oxygen-containing groups weakened. Based on these findings, 180, 240, 300, 360, 430, and 500 °C can serve as reference temperatures for optimizing cut points in industrial coal-tar fractionation. This study links TBP intervals with molecular composition and structure, providing a basis for precise fractionation, cut-point optimization, and targeted catalytic conversion.
Keywords: low- and medium-temperature coal tar; true-boiling-point distillation; simulated distillation; molecular composition; two-dimensional correlation infrared spectroscopy
Acknowledgments: National Natural Science Foundation of China (Grant No. U24A20552).

 

low- and medium-temperature coal tar; true-boiling-point distillation; simulated distillation; molecular composition; two-dimensional correlation infrared spectroscopy