Liptinite aromaticities

The elemental composition of the three maceral groups varies. The vitrinite, which frequently is about 85% of the sample in the United States, is similar to the patent coal. The liptinites are richer in hydrogen, whereas the inertinites are relatively deficient in hydrogen and richer in carbon. The liptinites also contain more aliphatic materials the inertinites are richer in aromatics. The term inertinite refers to the relative chemical inertness of this material, making it especially undesirable for Hquefaction processes because it tends to accumulate in recycled feedstock streams. 

The high-volatile Liddell bituminous coal (Figure 2 (E)) shows little indication of thermally-activated molecular mobility below 500 K. There is some fusion between 500 and 600 K followed by a major fusion transition above 600 K which appears very similar to the high temperature transition of the Amberley coal. This Liddell coal, however, has only 6% liptinite, has a crucible swelling number of 6.5 and exhibits considerable Gieseler fluidity. We therefore attribute this high temperature fusion event to the aromatic-rich macerals of the coal and associate it with the thermoplastic phenomenon. This implies that a stage has been reached in the coalification processes at which aromatic-rich material becomes fusible. 

The low-volatile bituminous Bulli coal which contains no liptinite and has significant thermoplastic properties has a M2J pyrogram (Figure 2 (F)) showing only one fusion transition which is lesser in extent and shifted to higher temperatures than that of the Liddell coal. This transition is, of course, attributed to aromatic-rich macerals. 

Two distinct types of fusible material occur in coals. One type is aliphatic-rich and associated with the liptinite macerals and the other is contained in the aromatic-rich macerals and particularly the vltrinites of bituminous coals. 

The rank dependence of the elemental composition of the maceral groups is shown in Fig. 9. The inertinites are the most aromatic, followed by the vitrinites and then the liptinites. Their oxygen contents decrease in the order vit-... 

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