Study on plasticity of maceral concentrates in terms of their structural features

In this study, two kinds of maceral concentrates, one is vitrinite-rich and the other contains about 50% inertinite, were prepared from the strongly coking coal, Australian Goonyella (GNY), and the weakly coking coal, South African Witbank (WIT), respectively, by density separation. These samples were submitted to chemical structural analysis such as solid-state ¹³C NMR and infrared spectroscopies, solvent swelling, selective oxidation, and estimation of the amount of transferable hydrogen, and thermogravimetric analysis. Inertinite-rich fractions ("A" samples) from both coals, which have little fluidity in a plastic range, have larger size of aromatic cluster, lesser amounts of substituents (alkyl- and oxygen functional groups) on aromatic rings, and higher density of cross-linking than vitrinite-rich fractions ("B" samples: higher fluidity) of same coal. For the appearance of high fluidity, relatively much aliphatic chains and bridges with WIT-B and branched aliphatic moieties and alicyclic parts with GNY-B sample, respectively, seem to be requisite, along with low aromaticity, much transferable hydrogen and high swelling index. Effective tar evolution took place in "B" sample between maximum fluidity temperature (MFT) and resolidification temperature (RT), while it occurred after RT in the case of "A" samples, these findings being parallel with observation reported previously. The authors rationalized these phenomena in terms of chemical reactions occurred during heat treatment.