Study of oxidization of coal–pitch by O3

For the purpose of obtaining small molecular and oxygen-containing aromatic compounds, taking a toluene-extracted coal pitch as the research object, the oxidation of coal–pitch by ozone (O3) in formic acid was studied. The coal–pitch sample and the oxidized pitch residue were characterized by elementary analysis and Fourier transform infrared spectroscopy (FTIR), while the small molecular products were analyzed by a gas chromatography–mass spectrometer (GC–MS). The results show that the highest oxygen content of oxidized coal pitch had been acquired at a reaction temperature of 50 °C, an O3 flow rate of 6300 mg/h and a reaction time of 4 h. Quite a lot of hydroxyls and carbonyls were introduced into the structure of the oxidized coal–pitch, while the small molecules produced mainly involve nonpolar aromatic compounds, aromatic anhydride and quinone compounds. It is speculated that the mechanism is direct electrophilic oxidation in which the molecules of O3 directly attack the aromatic ring at its carbon atoms with high electron density, and then generate hydroxyl or carbonyl until the aromatic ring cracks. This study shows that O3 can make the fused aromatic ring of coal–pitch become oxidized and depolymerized, and hence the ozonization of coal–pitch can be a potential method for obtaining oxygen-containing aromatic compounds.