Insight into aromatic structures of a middle-temperature coal tar pitch by direct characterization and ruthenium ion-catalyzed oxidation.

Highlights • Aromatic structures in CTP were investigated by direct analytical technologies and RICO. • Toxic PAHs and toxic equivalent of CTP were quantificationally analyzed. • CTP is rich in peri -condensed aromatics but poor in cata -condensed aromatics and polyaryls. • Oxygen existed as aromatic ether, while nitrogen and sulfur occurred in aromatic heterocycles. Abstract Aromatic structures dominated in a coal tar pitch (CTP), which play a significant role in the eco-environmental and effective utilization of CTP. Herein, a middle-temperature CTP was directly characterized by multiple instruments including solid-state (SS) 13C nuclear magnetic resonance spectrometer, X-ray photoelectron spectrometer, Fourier transform infraredspectrometer, X-ray diffraction and thermogravimetric analyzer, and then subjected to ruthenium ion-catalyzed oxidation (RICO), which aimed to providing the typical structural features of aromatic structures in CTP. Meanwhile, the carcinogenic polycyclic aromatic hydrocarbons (PAHs) in the CTP were quantitatively analyzed, and the toxicity was evaluated based on different standards. According to the direct characterization, CTP was rich in aromatic carbons, which accounted for 94.9% of total carbons. The average ring number of the aromatic clusters in CTP was 5, and aromatic rings were lowly substituted by methyl. Furthermore, the results from RICO of CTP implied that a series of cycloarylalkane structures exited in CTP. Peri -condensed aromatic structures were the most abundant, while the proportion of cata -condensed and biphenyl type structures were relatively small. This investigation provides a useful method for understanding the aromatic structures in CTP. [ABSTRACT FROM AUTHOR]