ONE-DIMENSIONAL DESCRIPTION OF THE AVERAGE POLYCYCLIC AROMATIC UNIT IN POCAHONTAS-NO-3-COAL - AN X-RAY-SCATTERING STUDY

The radial distribution method was used to examine the non-crystalline portion of a low-volatile bituminous coal, Pocahontas No. 3, from Buc hanan County, VA, USA. This coal, one of the Argonne Premium Coal Samp le Program, was used as received for X-ray absorption/diffraction/scat tering experiments. The diffraction due to the crystalline minerals co ntained in the coal and due to the graphene layering peak was removed from the amorphous scattering component. The latter was fitted to the self-scattering curve constructed from the scattering factor for carbo n and the difference was Fourier transformed to obtain the one-dimensi onal structural details of the average short-range structural unit in this coal. Interpretation of the radial distribution indicates that th e average structural unit is similar to 80% aromatic and consists of p olycyclic six-membered rings which are predominantly, if not exclusive ly, planar. In addition, the average graphene layer has a diameter of similar to 7.7 A. The radial distribution function results compare fav ourably with those obtained by C-13 NMR spectroscopy.