High sulphur coal sample from Ledo colliery of Makum coalfield, Assam, India was studied using FT-IR and XRD methods. FT-IR study shows the presence of aliphatic -CH, -CH 2 and -CH 3 groups, aliphatic C-O-C stretching associated with -OH and -NH stretching vibrations and HCC rocking (single and condensed rings). XRD pattern of the coal shows that it is amorphous in nature. Function of Radial Distribution Analysis (FRDA) indicates that coal is lignite in type and there is no evidence of graphite-like structure. The first maximum in the G(r) plot of FRDA at r = 0.14 nm relates to the aliphatic C-C bond (Type C-CH=CH-C), the second maximum at r = 0.25 nm relates to the distance between carbon atoms of aliphatic chains that are located across one carbon atom. The curve intensity profiles obtained from FRDA show quite regular molecular packets for this coal. The coal was found to be lignite in nature.

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The so-called turbostatic structure of carbons in coal with randomly oriented stacking of the lamellae (graphene) produces intense peaks, which are the dominant features in its X-ray diffraction profiles. The diffractogram may be conveniently divided into two regions of reciprocal space, the medium S region (1 < S < 3 Å) and a high S region (S > 3 Å) where S = 4πλ -1 sinθ. To better understand the molecular level structure of high sulphur Assam coal, two coal samples (Tirap-1 and Tirap-2) from Tirap colliery of Makum coalfield, Assam (India) has been interpreted in this study by using the X-ray diffraction profiles. Random layered (graphene) structural parameters of these coals were determined by using X-ray diffraction technique, which showed that the L a and L c are 64⋅99 Å and 22⋅63 Å for Tirap-2 and 55⋅54 Å and 23⋅80 Å for that of Tirap-1 coals respectively. The position of γ band was found to be at 4⋅34 Å and 4⋅13 Å for Tirap-2 and Tirap-1 coals respectively. The number of layers and average number of carbon atoms (N) per aromatic graphene were found to be 21 and 8 for both the coal samples. Proximate, ultimate and ash analysis of the two coal samples were also carried out in this investigation.

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An examination on the structural features of some coal samples from Makum coalfield, Assam (India) were carried out by using scanning electron microscopy. The morphological characteristics of the macerals were recognized. Collinite was recognizable by its angular shape with characteristic fracture patterns and striated or laminated surfaces. Sporinite particles showed no well-defined shape. Fusinite was remarkable in having a chunky needle form. Chemical and petrographic characteristics of these coals also have been reported. These findings have shown prime importance in fingerprinting the physical structure of these coals.

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The formation of onion-like fullerene and chemically converted graphene-like nanosheets from low-quality coals were observed during an oxidation-cum-extraction (OCE) process.

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