Effects of thermal treatment on the composition and properties of air-blown anthracene oils

Eight parent samples, obtained from a commercial anthracene oil by air-blowing under different conditions, were thermally treated in nitrogen between 350 and 390°C for 3–8 h. Changes in the composition, pyrolysis behaviour and microstructure of the resultant cokes were studied by standard procedures (i.e. elemental analysis, softening point, etc.), Fourier transformed infrared spectroscopy, size exclusion chromatography, thermogravimetric analysis, mass spectrometry and optical microscopy. The results show that thermal treatment causes the removal of hydrogen (mainly aliphatic) and a considerable amount of the oxygenated functionalities created during the air-blowing treatment. As a result, H2O, CO and CO2 are removed and new C–C bonds are formed producing larger molecules with a higher degree of condensation. Consequently, the toluene insolubles, softening point and carbon yield of the treated samples substantially increase their values. Thermal treatment also improves the quality of samples as carbon precursors and increases graphitisability and resistance of the derived cokes to oxidation.