Separation and analysis of maceral concentrates from Victorian brown coal

Four selectively mined lithotypes and a run-of-mine coal (ROM) have been obtained from the Yallourn coal seam in the La Trobe Valley, Victoria, Australia and a partial maceral separation of each of them has been carried out using the sink-float method with centrifugal force on a laboratory scale. The yields of liptinite-rich float fractions were between 22.5 and 2.8 wt% in the order of Pale > Light > Med-light ≈ ROM > Dark. Elemental analysis and FTIR showed that the liptinite-rich float fractions had higher H/C ratios and aliphaticities than the corresponding vitrinite-rich sink fractions and this was confirmed by solid state ¹³C NMR. Pyrolysis-GC-MS using a pyrolysis temperature of 650 °C showed little difference in the distribution of aliphatic peaks but dramatic changes in the relative abundance of triterpenoids between lithotypes and in some cases between float and sink fractions of a lithotype. Variations in yields with pyrolysis temperature suggested that the triterpenoids are loosely bound to the main coal structure.