Groups of Macerals

Semifusinite is also included in the vitrinoid group of macerals. It is distinguished from fusinite by a degree of translucence in thin section and lower reflectivity in polished specimens. Semifusinites may be subgrouped according to appearance, which however was not attempted. The semifusinites very often occur as a transition stage between vitrinoids and fusinoids. 

Inertinite group of macerals composed of fusinite, inertodetrinite, macrinite, micrinite, sclerotinite, and semifusinite. 

Liptinite group of macerals composed of alginite, cutinite, resinite, and spori-nite derived from secretions of plants and distinguished from one another... 

As Stopes seems to have anticipated, a large number of macerals have been identified and named. All macerals, however, can be conveniently grouped into three major subdivisions -vitrinite, liptinite, and inertinite. The vitrinite group of macerals are derived from plant cell wall material (woody tissue) and usually make up 50-90% of most North American coals. Although there are a large number of named varieties of... 

The major petrographic feature of the liptinite group of macerals is that they all have a reflectance that is lower than the vitrinite macerals in the same coal. This group of macerals is very sensitive to advanced coalification and the exinite macerals begin to disappear in coals of medium-volatile rank and are absent in coals of low-volatile rank. When the exinite macerals are present in a coal, they tend to retain their original plant form and thus they are usually plant fossils phyterals). The phyteral nature of the liptinite macerals is the main basis on which they are classified. 

Coals are not homogeneous but are made up with macerals, these being recognizable components (by optical microscopy) within the coal derived from specific plant components. Coals may possess different quantities of macerals so accounting for small differences in rank. The exinite group of macerals exhibit maximum fluidity, the vitrinites have an intermediate position and the fusinites (like a wood charcoal) are non-fusible. 

Table 1. Stopes-Heerlen Classification of Maceral Groups, Macerals, and Submacerals of Higher Rank Coals ...

Of the three major groups of petrographic constituents (termed macerals see appended note), vitrinites and exinites ... 

Both groups of spectra show greater complexity than the spectra of resinites from bituminous coals, particularly in the region below 1250 cm. 1 in which numerous but generally weak absorption bands occur. A complete and realistic interpretation within this region would be virtually impossible without considerable chemical study, and it was not the intention of the present investigation to cope with this problem. It was hoped to establish how the absorption pattern of lower rank resinites compared with that of the maceral in bituminous coals and in particular to see what spectral characters were possessed by possible precursors of bituminous coal resinites. 

Aliphatic structures are still of major importance in the second group of resinites, those of the bituminous coals, but aromatic structures are present in significant amounts. The spectra of these resinites display the type of absorption pattern that has come to be associated with other coal macerals, particularly the sporinites and to a large extent the vitrinites. This pattern is established in the resinites of the high volatile bituminous coals. Furthermore, resinites of this group are reactive during carbonization and oxidation processes in which their behavior parallels that of similarly affected vitrinites of equivalent rank. 

The preparation of maceral concentrates for study has been achieved by one of two approaches, either by hand picking or by a variety of techniques which exploit the variation in density between the various maceral groups. The first level of hand picking is the judicious sampling of lithotypes. This term is used to identify the various layers found in a coal seam. For humic coals there are four main designations of lithotypes vitrain, clarain, durain, and fusain (42). Vitrain bands are sources of fairly pure vitrinite group macerals while fusinite and semi-fusinite can be obtained from fusain. These are the... 

Our recent development of a new procedure for the density separation of macerals offers a method for obtaining high resolution separation of the three maceral groups exinite, vitrinite, and inertinite, and can further resolve individual maceral types within these macerals groups, e.g., sporinite from alginite in the exinite group (1,2). The procedure... 

Of particular interest in this study is the nature of the non-aromatic structures in the three main maceral groups. It should be noted that the exinites in both the coals separated by float-sink are 90% sporinite. It has been theorized that small molecules, especially the aliphatics, are fairly mobile at some period during the formation of coal (5,6). The studies which support this theory were done on coals that are very rich in exinites and some contained alginite. Two of the coals chosen in the present work (PSOC 828 and 1103) have a more normal distribution of macerals and yet the pyrolysis results indicate that migration of molecules from the exinites to vitrinite and then incorporation into the macromolecular structure might have occurred. 

The yields of the reaction of maceral concentrates with pyridine and iodine show some interesting trends and are given in Table V. Unlike the results from the thermal reactions such as vacuum pyrolysis (Table IV) or short contact time liquefaction (29), the vitrinites are more reactive than the spori-nites. The inertinites are less reactive but the magnitude of the difference in the comparison with the other maceral groups from the Indiana and Kentucky coals is much less than what has been found for the yields from the thermal reactions. 

Examination of the Py-MS results may provide some understanding of the variation observed between the different maceral types. A distribution pattern of the type shown in Table III has been determined for a select number of macerals which also have been reacted in the pyridine-iodine mixture. In examining the three different possible cases for activation of coal maceral benzylic groups, [1] and possibly [3] would appear to be the most important. From the Py-MS results alkyl pyridines have been found to be much less abundant than alkyl phenols which is not surprising considering the percentage of oxygen compared to... 

The hydrogen atom exchange reactions between Tetralin and diphenylmethane and the reduction of the ketones were studied in the presence of a selected group of raw whole coals, demineralized whole coals, and demineralized macerals. The macerals used in this work were obtained from two hvA bituminous coals, one from the Kentucky Upper Elkhorn No. 3 Seam (PSOC-1103) and one from the Ohio Lower Kittaning No. 5 Seam (PSOC-297) two hvB bituminous coals, one from the Indiana No. 1 Block Seam (PSOC-106) and one from the Hiawatha King 6 Mine and two hvC bituminous coals, one from the Illinois No. 2 Seam and one from the Indiana Brazil Block Seam (PSOC-828). 

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