Vitrinite chemical composition

Determination of maturity levels is critical to the success of any exploration program. Recovery of immature, but organic-rich, source rocks would indicate good source potential for such rocks if buried more deeply in other parts of the basin. At the other extreme, an overmature source rock would indicate a mature part of the basin not capable of generating additional liquid hydrocarbons, but possibly gas. There are several indicators available that can be used to estimate the relative maturity of a source rock. The traditional method is measuring the maturity of vitrinite. The chemical composition of the maceral... 

If sufficiently abundant, this material can cause suppression of vitrinite reflectance and will fluoresce under UV/blue light when immature (Price Barker 1985 Wilkins et al. 1992). With increasing maturity all the components in Fig. 4.3 become increasingly similar in chemical composition and follow evolution paths leading towards the origin. The chemical changes lead to... 

The maceral content defines the coal type sapropelic, with >50% liptinite, or humic, more abundant, usually presenting a banded structure. On the other hand, based on the different optical properties of macerals, the reflectance of vitrinite is an essential characteristic used in coal identification and related to rank. A good analysis of maceral content provides knowledge about the chemical composition of a coal, their behavior in different conversion processes, and can also be used as a parameter of coal rank (see section on Petrographic analysis). 

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. 

Extended discussion of these speculative relationships is unwarranted until more critical information is available. The multilinear aspect of coalifi-cation described previously (3, 6) appears to be well illustrated by the Brandon woods. It seems evident that from a single plant tissue various dissimilar materials may result as products of coalification. Those described represent macerals related to the vitrinite, micrinite, and resinite maceral series. Because of the position of these materials in their respective series—i.e., only slightly metamorphosed and anatomically relatable to the woods of extant plants— their detailed study using appropriate chemical and physical methods should reveal useful information concerning the basic composition of coals of both higher and lower rank and simultaneously add to our knowledge of the coalification process. 

For purposes of clarity, the CP/MAS spectrum of PSMC-67 is given in Figure 5 as a composite of - C chemical shifts of structural units containing H, C and 0 (32). The vitrinite... 

Coal rank from the petrographic point of view is commonly expressed in terms of vitrinite reflectance which may act as an indicator that is independent of other factors (e.g., coal type or grade). Unlike other chemical parameters (e.g., carbon content, hydrogen content, volatile matter yield, and calorific value) it is not dependent on the overall composition of the coal. A number of coal properties progressively change with the advance in rank and the rank of a coal is therefore a major factor influencing its potential application. 

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