Humic coal

The conditions of pyrolysis either as low or high temperature carbonization, and the type of coal, determine the composition of Hquids produced, known as tars. Humic coals give greater yields of phenol (qv) [108-95-2] (up to 50%), whereas hydrogen-rich coals give more hydrocarbons (qv). The whole tar and distillation fractions are used as fuels and as sources of phenols, or as an additive ia carbonized briquettes. Pitch can be used as a biader for briquettes, for electrode carbon after coking, or for blending with road asphalt (qv). 

In on effort to establish the mechanism of coal flotation and thus establish the basis for an anthracite lithotype separation, some physical and chemical parameters for anthracite lithotype differentiation were determined. The electrokinetic properties were determined by streaming potential methods. Results indicated a difference in the characteristics of the lithotypes. Other physical and chemical analyses of the lithotypes were mode to establish parameters for further differentiation. Electron-microprobe x-ray, x-ray diffraction, x-ray fluorescent, infrared, and density analyses were made. Chemical analyses included proximate, ultimate, and sulfur measurements. The classification system used was a modification of the Stopes system for classifying lithotypes for humic coals. 

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... 

Kreulen reported that Rasa coal was a humic coal and contained no sapropelites, waxes, or resins (4). He noted that Rasa coal exhibits dual character, i.e., it exhibits both low- and high-rank characteristics. Chemical tests indicated that a small amount of the sulfur present is in side chains, and a large amount occurs in ring structures. Using a statistical structural analysis method based on density, van Krevelen computed that 59% of the carbon in Rasa coal is aromatic (4). 

Monthioux M., Landais P., and Monin J.-C. (1985) Comparison between natural and artificial maturation series of humic coals from the Mahakam delta, Indonesia. Org. Geochem. 8, 275-292. 

Pyrolysis in the presence of TMAH has also been applied to the structural characterization of HAs isolated from low-rank coals. Figure 6 shows the chromatogram of the compounds released after the TMAH/pyrolysis of the HA isolated from a humic coal from Konin (Poland). A large variety of components were released, the lignin-derived phenol derivatives and aliphatic acid methyl esters being the most prominent. A series of fatty acid methyl esters were identified in the range from Cio to C34, with maxima at C16 and Cig showing an even-over-odd... 

A series of experiments has been carried out to observe the generation of the different classes of oil constituents. Aliquots of two kerogens from the Green River Shale (type I) (6) and the Lower Toarcian shales of the Paris Basin (type II) (7) where heated at a constant heating rate of 4°C min to different final temperatures ranging from 375°C to 550°C. A humic coal from Indonesia (type III) was also used for comparison (8). These various... 

X xylenes) generated from humic coal (type III) as compared to those generated from oil shales (types I and II). 

FigureS. Hydrocarbons generatedfrom the two main types ofoil shales by pyrolysis at 4 °C min l rate up to 500 °C. Hydrocarbons generated from a humic coal (Type III) are...

Organic petrography and organic element analysis reveal that the source of the kerogen is algal (lamosites dominating) while other maceral forms dominate locally to form carbonaceous shale and humic coals. 

Coal is formed from peat and the vascular plant remains that accumulate in peat bogs. Anaerobic conditions are considered mandatory for the accumulation and preservation of peat and the formation of coal. Two major types of coals are known humic coal and sapropelic coal (see Breger, 1963, 1976). The former are formed from peat accumulations rich in humic substances derived predominantly from vascular plant remains. The latter represent coal formed from algal (boghead coal) or spore (cannel coal) accumulations. In many respects, sapropelic coal can be considered to have an aquatic origin similar to that of humin of aquatic sediments which forms from the accumulation of aquatic nonvascular plant debris in clastic sediments. Conversely, kerogen can also have the properties of humic coals (Breger and Brown, 1962) is the source materials to the sediment at the time of deposition are predominantly derived from vascular plants. 

Various combinations of maceral groups occur in humic coals but four main lithotypes are recognized on the macroscopic scale vitrain (comprising mainly vitrinite), durain (comprising liptinite and inertinite), clarain (comprising vitrinite and liptinite) and fusain (mainly fusinite, with some semifusinite). On the mi-... 

There are two main phases in the formation of humic coals peatification, followed by coalification. Coali-... 

Fig. 4.5 Van Krevelen diagram showing the main evolutionary trends of sapropelic (cannel and boghead) and humic coals (after Durand et al. 1983). Rank increases towards the origin brown coal = lignite + sub-bituminous coal).

The relatively minor hydrocarbon liquids that are generated by most humic coals are characteristic of higher plant material. Coal-sourced oils are generally dominated by cuticular-wax derived fi-alkanes, although benzene, naphthalene and phenanthrene and their alkyl derivatives are usually important. Small amounts of larger aromatic hydrocarbons formed from... 

Fig. 5.11 Possible origins of etio porphyrins in sediments and humic coals (after Barwise Roberts 1984 Bonnett et al. 1984 Baker Louda 1986 Louda et al. 1998).

Often the higher plant derived terpanes are found in association with their aromatic counterparts. For example, among the aromatic diterpenoids that can dominate the methylated phenanthrenes of bitumens from humic coals are retene, formed from abietoids and phyl-locladoids (Fig. 5.18), and pimanthrene from pimaroids (Fig. 5.30). Similarly, diagnostic pentacyclic aromatic hydrocarbons may be present in ancient sediments and oils, such as 1,2,9-trimethylpicene (derived from 0C-amyrin Fig. 5.22) and 1,8-dimethylpicene (derived from (3-amyrin Fig. 5.30). Abundant 1,2,7-trimethyl-naphthalene relative to other trimethylnaphthalenes... 

Fig. 5.30 Two higher-plant derived aromatic hydrocarbons that can be found in bitumens from humic coals.

An extreme case of early formative history determining the chemistry and physical properties of coal, well-known for over 100 years, presents itself in the differences between humic and sapropelic coals, that is, between coals that developed in partially aerobic and wholly anaerobic stagnant environments, respectively. It is therefore quite unreasonable to assume that the components of humic coals, which developed from plant debris that decayed in environments as different as high moors and deltaic swamps, were substantially unaffected by depositional influences and are therefore unified by a rank-dependent chemistry. 

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