Abstract of Recent Work: The Nature of Resnite in the Herrin No. 6 Coal Seam

Background: Resinite is a naturally occurring substance found in coal that is derived from original plant resins. It is ubiquitous in North American coals. It makes up one to four percent by volume of most Illinois coals. In the western U.S.A. it has been commercially exploited for use in adhesives, varnishes and thermal-setting inks. The chemical structure of resinite has only recently been studied in detail with advanced analytical methods such as pyrolysis mass spectroscopy and nuclear magnetic resonance. One problem is that there are a variety of resinite maceral types with a variety of chemical structures. Resinites are derived from a great number of plant resins. Indeed, a single plant can have more than one kind of resin. These resins are then subjected to diagenesis and coalification which can modify the resinite structure. There is even abundant evidence that some of the resinite in coal is secondary and derived from exudates expelled from the coal mass during coalification. Although most of the published studies on resinite structure deal with resinites from Cretaceous and younger coal, there is some published data to indicate that Carboniferous resinites are quite different structurally.

Objective: The overall objective of this study was to compare the properties of the resinite contained in Illinois Basin coals to resinite being commercially exploited in the western United States.

Procedures: Pure concentrates of resinite from IBCSP 101 (Herrin No. 6 Seam) were produced by the density gradient centrifugation technique. The resinite had an apparent density in aqueous cesium chloride of 1.13 g/mL. The pure resinite concentrates were analyzed petrographically and with pyrolysis gas chromatography-mass spectrometry

Results: The results of the petrographic study of this pure resinite show that it occurs as primary ovoid bodies (see Figures 1-2). The separated resinite had similar petrographic features (see Figure 3). The results of pyrolysis gas chromatography-mass spectrometry have shown that the Illinois resinite is almost entirely aliphatic in nature showing a spectrogram of straight chain n-alkanes, n-alk-1-enes, and n-alk-dienes (see Figure 4). These results are supported by the results of nuclear magnetic resonance analyses that show almost all of the carbons to be aliphatic. These results are in contrast with the results of the same kind of analysis on resinite separated from the Hiawatha seam from the Wasacth Plateau in central Utah which are clearly sesqiterpinoid in nature (see Figure 5).

Fig. 1

Fig. 2

Fig. 3

Fig. 4

Fig. 5

Conclusion: In summary, the macerals in Illinois coals of Pennsylvanian age that are universally identified as resinites have a polyethylene-like structure which is significantly different from the terpinoid structure of the resinites from the Hiawatha seam coals of Cretaceous-Tertiary age.

References:

Han Z., Kruge M. A., Crelling J. C., and Bensley D. F., Classification of torbanite and cannel coal I: Insights from petrographic analysis of density fractions: International Journal of Coal Geology, in press

Crelling, John C., and Kruge, Michael A., Petrographic and chemical properties of resinite from the Herrin No. 6 coal seam: International Journal of Coal Geology, in press.

Crelling, John C., 1995, The petrology of resinite in American coals: In , Anderson Ken B. and Crelling , J. C., eds., Amber, Resinite, and Fossil Resins, ACS Symposium Series 617, American Chemical Society, Washington, D. C., p. 218-233.

Kruge, Michael A., Stankiewicz, Artur B., Crelling, John C., Montanari, Alessandro, and Bensley, David F, 1994, Fossil Charcoal in Cretaceous-Tertiary boundary strata: Evidence for catastrophic firestorm and Megawave: Geochemica and Cosmochemica Acta, v. 58, no. 4, p. 1393-1397

Crelling, John C., Pugmire, Ronald J., Meuzelaar, Henk L.C., McClennen, William H., Huaying Huai, and Karas, Jirina, 1991, Chemical structure and petrography of resinite from the Hiawatha "B" coal seam: Energy and Fuels, v. 5, no. 5, p. 668-694.