Formation of mesophase spherules in low-Ql coal tar pitches and development of monolithic carbons therefrom

Three coal tar pitches having different and low contents of primary quinoline insolubles (Ql) were subjected to a series of thermal treatments at a predetermined temperature for different periods of soaking. The development of mesophase, in terms of its size and content in the heat-treated pitches, was studied as a function of the soaking time and content of primary quinoline insolubles in the original pitches. Mesophase spherules, with an average size of about 5 m, formed in one of the coal tar pitches were separated using solvent extraction employing a suitable tar oil. These spherules, also called mesocarbon microbeads (MCMB), after being moulded into small rectangular plates, were carbonized at temperatures of 950 and 2700 °C to obtain fine textured monolithic carbons possessing apparent densities of 1.66 and 1.85 g cm^–3, respectively, at these heat-treatment temperatures.