Maceral inertinite

Macerals. Coal parts derived from different plant parts, are referred to as macerals (13). The maceral names end in "-inite" as do the mineral forms of rocks. The most abundant (about 85%) maceral in U.S. coal is vitrinite, derived from the woody tissues of plants. Another maceral, called liptinite, is derived from the waxy parts of spores and poUen, or algal remains. The liptinite macerals fluoresce under blue light permitting a subdivision based on fluorescence. A third maceral, inertinite, is thought to be derived from oxidized material or fossilized charcoal remnants of early forest fires. 

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. 

There are certainly lithotypes that can be handpicked from European and American coals that are relatively rich in fusinite and semifusinite. However, it is perhaps significant that the mean content of total fusinite + semifusinite in 697 coal samples in the Penn State/DOE Data Base is 8.9%. On the other hand, the content of inertinite macerals in the Permian coals of Gondwana-land is notoriously high and much of this inertinite material consists of semifusinite (5,26,33,34), the concentration of which can be as high as 50% in the whole seam. 

Earlier publications have documented the higher reactivities of vitrinite and liptinite group macerals and the lower reactivities of certain inertinite macerals in liquefaction (50,57,68). 

For American and European coking coals the behaviour of semi-fusinite is generally less important since only small quantities of this maceral are usually present. However, South African coal used in coke oven-blends contains as little as 40 per cent vitrinite and as much as 45 per cent reactive semi-fusinite (12). The partial reactivity of the semi-fusinite fraction during liquefaction of Australian coals has been reported by Guyot et al (13). They found that the low reflecting inertinite in two coals up to (a reflectance from 1.40 to 1.49) was reactive. This agrees with the results of Smith and Steyn (12) who consider that the semi-fusinite fraction in South African coals up to V- 5 (1.50 - 1.59) can be reactive to coking. 

For example, Beynon and Cwm coals when digested in anthracene oil give extraction yields of 68% and 47% respectively. This variation can be explained by reference to the maceral composition of the coals. Beynon coal contains a lower concentration of inertinite than the Cwm coal (Table V). In experiments where relatively pure samples of petrographic species were digested in anthracene oil, exinite and vitrinite were shown to be highly soluble, whilst in comparison the inertinite was almost completely insoluble. Similar variations in reactivity of macerals have been reported from studies of solubility in pure organic solvents (1(3). 

Liptinites were made up of hydrogen-rich hydrocarbons derived from spores, pollens, cuticles, and resins in the original plant material. Vitrinites were made up of wood, bark, and roots and contained less hydrogen than the liptinites. Inertinites are mainly oxidation products of the other macerals and are consequently richer in carbon. The inertinite group includes fusinite, most of which is fossil charcoal, derived from ancient peat fires. 

Note These (maceral) constituents can be identified and quantitatively measured by examining thin sections or polished surfaces under a microscope, and reflect the nature of the primordial source material as well as the conditions under which it was deposited. Vitrinites derive from humic gels, wood, bark and cortical tissues eoi lnites are the remains of fungal spores, leaf cuticles, algae, resins and waxes and inertinites comprise unspecified detrital matter, "carbonized" woody tissues and fungal sclerotia and mycelia. 

The relative degree of denseness (i.e., opacity to electrons) of the macerals is exinite least dense, vitrinite intermediate, and inertinite most dense of the coal maceral groups. That is, the light/dark relations are similar to those observed in the usual thin sections examined in the light microscope. 

The composition of the volatile matter evolved from coal is, of course, substantially different for the different ranks of coal, and the proportion of incombustible gases increases as the coal rank decreases. Furthermore, in macerals isolated from any one particular coal, the volatile matter content decreases in a specific order thus, exinite produces more volatile matter than vitrinite, which, in turn, yields more volatile matter than inertinite. 

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

Inertodetrinite maceral occurring as individual, angular, clastic fragments of other inertinite macerals, surrounded by other macerals, commonly vitrinite or minerals, and also distinguished by a reflectance higher than that of associated vitrinite. 

Vitrinite maceral and maceral group composing all or almost all of the villain and like material occurring in attrital coal as the component of reflectance intermediate between those of exinite and inertinite. 

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... 

D. Inertinite macerals, seini-fusinite at left and fusinite at right. 

Free Radicals in Macerals. Electron spin resonance (ESR) has been used to study carbon free radicals in coals, and to some extent, separated macerals. The technique provides information on radical density and the environment of the radicals. The resonance position, termed the g-value, is dependent on the structure of the molecule which contains the free electron. The line width is also sensitive to the environment of the unpaired electron. In an early study, Kroger (71) reported that the spin concentration varied between maceral groups with liptinite < vitrinite inertinite. For this limited set of samples the spin concentration increases with rank for liptinites and vitrinites and decreases for the micrinite samples. On the other hand, van Krevelen (72) found the same general results except... 

Product characterization from liquefaction has not been extensive. Phi 1p and Russell (95) have examined products by Py-GCMS from metal halide catalyzed hydrogenation of a vitrinite, alginite, and inertinite, each from a different source. They were able to correlate Py-GCMS results with reaction temperature. King, et al. (96) examined the short contact time liquefaction of macerals separated by DGC from a single hvB bituminous coal. They found correlations between density and reactivity and composition of the products. 

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... 

Part of this data in Table II is a series of British maceral concentrates. The Woolley Wheatly Lime sample is 93% fusinite while the Teversal Dunsil concentrate is 80% semifusinite with 13% fusinite. The Aldwarke Silkstone sample contains 43% semifu-sinite and 43% fusinite. The petrographic analysis of PSOC-2 reveals nearly equivalent amounts of fusinite, semifusinite, micrinite, and macrinite (6.8, 8.1, 7.5 and 8.5% respectively in the whole coal) while PSOC-858 contains primarily semifusinite as the inertinite. The differences in faH values for these iner-tinite samples are greater than the experimental error and these differences suggest that NMR techniques may be useful in characterizing the chemical structural differences between inertinite macerals. 

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