Vitrinite and exinite

The reported values fully agree with those found by other investigators (2, 8) on exinites, vitrinites, and micrinites of the same rank. The atomic H/C... 

The values of %Hoh in column 5 are the difference between %H and (%H.r + %H.t), and agree fairly well with those which follow from the experimentally determined %Ooh (I, 2). Furthermore, it can be seen from the results in Table II that H.r/H increases considerably, and consequently Hai/H decreases strongly in the sequence exinite, vitrinite, and micrinite. 

Table III. Aliphatic Hydrogen Distribution Derived from PSR Measurements and H.i/H for an Exinite, Vitrinite, and Micrinite...

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... 

E, V, and I refer to exinite, vitrinite, and inertinite. The relative concentration has been normalized to absolute units for each coal. 

There have been a large number of electron spin resonance (ESR) studies of coal and coal products,(1J but a microscopic interpretation of the resulting data has been hampered by the chemical heterogeneity of the coal samples examined. While several surveys of specially selected macerals have appeared, 3), the recent evolution of maceral separation techniques - now allows detailed ESR observations to be made on coals systematically fractionated in which coal rank, maceral type, and maceral density are simultaneously distinguished. The present report surveys the behavior of a variety of ESR properties of carbon radicals in exinite, vitrinite, and inertinite macerals in a variety of coals of different rank. These data... 

In a study of the organic structures 1n coals and their reactivity in chemical and thermal processes, it is desirable to reduce the complexity of the material by some sort of physical separation. One such approach is the separation of the coals into their maceral groups, which are the microscopically identifiable organic portions of coal which may have different origins, chemical and physical features, and reactivity. Two bituminous coals have been separated into their three main maceral groups exinite, vitrinite, and inertinite, using a modified... 

Benzophenone, as mentioned in the Introduction, has been used to assess the hydrogen donor capacity of coals (11, 12). Unfortunately, most coals react very slowly with this compound at 400°C, equation 1. For example, less than 57o of this ketone is converted to diphenylmethane by a vitrinite-rich sample of Illinois No. 6 coal in benzene in one hour at 400°C. Preliminary work revealed that the exinite, vitrinite, and inertinite isolated from PSOC-828 exhibit small, but apparently significant... 

Smith, G.C. and Cook, A.C. 1980. Coalification paths of exinite, vitrinite and inertinite. Fuel, 59 641. 

For example, as the carbon content of the coal increases, the active thermal decomposition occurs in successively higher temperature ranges and the maximum weight loss decreases quite substantially (Figure 13.10). In addition, different macerals in any one particular coal also generate different amounts of volatile matter, and, thus, similar trends are noted when exinites, vitrinites, and inertinites of the same rank are thermally decomposed (Figure 13.11). 

In Figure 9 the vitrinite + exinite content and the reactive maceral content, as determined by ISCOR, are plotted against the total conversion for the hot-rod technique. Figure 10 plots the same information for the autoclave results. 

It is possible to produce some liquid hydrocarbons from most coals during conversion (pyrolysis and hydrogenation/ catalytic and via solvent refining)/ but the yield and hydrogen consumption required to achieve this yield can vary widely from coal to coal. The weight of data in the literature indicate that the liquid hydrocarbons are derived from the so-called reactive maceralS/ i.e. the vitrinites and exinites present (7 8 1 9). Thusf for coals of the same rank the yield of liquids during conversion would be expected to vary with the vitrinite plus exinite contents. This leads to the general question of effect of rank on the response of a vitrinite and on the yield of liquid products and/ in the context of Australian bituminous coals, where semi-fusinite is usually abundant/ of the role of this maceral in conversion. 

The coal studied, 78% C and 15.8% 0 daf, is derived from Carboniferous deposits from the Ziemowit mine in Poland. Its petrographic composition /% vol. dmmf/ is vitrinite, 60 exinite, 12 and inertinite, 28. 

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

Figure B. Clarite with microspores in a high volatile bituminous coal (37% V. M.). Above untreated, below after a-irradiation. The reflectance of vitrinite and exinite increased to the degree of reflectance of a medium volatile coal (with 26% V. M.). Polished section, oil immersion, X 500 (from Brennstoff-Chemie 46, 13 (1965))...

The physical or petrographic components of coal are defined or described in various ways. In one system, which depends on microscopic observation, the principal components are called exinite, vitrinite, micrinite, and fusinite. Transparency of these in a thin section decreases in that order, whereas reflectance from polished surface increases in the same order. Vitrinite, the major component of most coals, occurs in bands or strands and is usually uniform in appearance, though sometimes shows cell structure exinite consists of the remains of plant spores, pollen, and cuticles with characteristic shape micrinite occurs in very fine granular form or massive structureless, irregular form fusinite shows characteristic fibrous, cellular structure. Semifusinite is transitional between vitrinite and fusinite. On a macroscopic scale, vitrain and... 

Examination of ultrathin tactions of coal in tko aloctron microscope hat revealed that one type of vitrinite (vitrinite A) it homogeneous, while the remaining vitrinite (vitrinite B) it a two-component material, the components having similar properties to vitrinite A and exinite, respectively. The material similar to exinite occurs in sheets no more than 1000 A. thick and is responsible for the lower reflectance and higher volatile matter yield of vitrinite B. Exinite, micrinite, and semifusinite have been identified in ultrathin sections. By using a technique of impregnation with a lead salt the ultrafine pore structure of vitrinite has been made visible. 

Apart from the exinite and micrinite, all the other coal material in this section is vitrinite and would be counted as such in a maceral analysis. These macerals were identified not only from their form, which is often characteristic, but by direct comparison of the light-microscope picture of the facet from which the ultrathin section was cut (I). By using this technique, each maceral occurrence of sufficient size could be positively identified. 

Since the structural parameter H.i/C i cannot be determined experimentally, only particular f. values can be derived for example, the theoretically highest fm value follows from the assumption that H i/C i = 3, which means that the entire aliphatic portion consists of CH3 groups. A more realistic value of fm follows if in Equation 2 H.1/C.1 = 2 (the aliphatic portion consists either only of CH2 groups or of the same number CHa and CH groups with or without CH2 groups) is used. These two theoretical but meaningful / values are 0.92 and 0.88 for the micrinite, 0.84 and 0.77 for the vitrinite, and 0.75 and 0.82 for the exinite. 

The number of CH-.> groups per 100 of the exinite is more than the double of that of the vitrinite and six times higher than that of the micrinite. Thus, it is very probable that to a first approximation HLi/Cai of the exinite equals 2, a value which corresponds to / = 0.62. The most probable / value for the vitrinite has been found to be 0.77 (4), a value which also requires Hai/Ch near 2. For the micrinite an f value — 0.89 seems reasonable. 

The values in Table VII show that 12 nonaromatic rings should be present for nine mean structural units in the case of exinite, 10 in the case of vitrinite, and 16 in the case of micrinite. Since all faiIt -Rnnr) values are higher than the highest ones obtained from the aliphatic group distribution (see Table IV), all samples must contain nonaromatic rings even if the most probable / values... 

Table VIII shows that in the case of the exinite and the vitrinite C n i > is determined by 2 R.i of the micrinite is given by the smallest value for C Cai only for the exinite for the vitrinite and the micrinite it follows from the highest value for C

Samples Studied. From British Seams. The suite of samples was collected and separated by the Coal Survey of the National Coal Board under the direction of Dr. G. W. Fenton, and the authors are indebted to Dr. Fenton for the gift of the samples. The suite consisted of the vitrinites, spore-rich exinites, fusinites and, in one case, the micrinite from five British coal seams of Carboniferous age together with the vitrinites from two coals of higher rank from which it was impracticable to separate the other macerals. The exinites were separated by float-and-sink methods from selected black durain bands, as also... 

Ash content 0.3-1.096 for vitrinites and exinites. 2-4% for fusinites and micrinite. For reflectance of fusinites see Figure 1. 

Results on Unheated Samples. The results obtained in Southampton for the set of British samples are shown in Figures 2 and 3. In Figure 2 the spin concentration of each maceral is plotted against the carbon content (daf) of the associated vitrinite, and the points for each set of macerals from one coal are joined by a vertical line. It can be seen that the vitrinite series forms a well-defined narrow band which curves upwards sharply at about 90% carbon, and the data resemble closely those presented earlier by Austen and Ingram for whole coals. The values of exinites form a wider, approximately horizontal band lying a little below the vitrinite band, while the fusinite data appear to vary at random but lie consistently well above the vitrinite band and are appreciably higher than vitrinites of the same carbon content (90-92%) would be. 

All three possible explanations of the presence of relatively high concentrations of unpaired spins in vitrinites and exinites from bituminous coals seem reasonably plausible. It is likely that all three mechanisms made some contribution, but one cannot at present assess their relative importance. 

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