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13C nuclear magnetic resonance spectroscopy with cross polarisation and magic angle spinning (CP-MAS NMR) has been used successfully to study the distribution of carbon types in a wide range of coals, their precursors and chars. The chemical changes occurring during coalification are essentially the same as those observed during inert pyrolysis, and include dealkylation, loss of carbon types associated with oxygen-containing functional groups, and increasing condensation of aromatic ring systems. Although derived exclusively from NMR data, this model agrees well with more conventional models of coalification developed by chemical methods. Difficulties were experienced in obtaining satisfactory 13C CP-MAS NMR spectra of coal chars prepared by inert pyrolysis at temperatures above 700 C. Proton magnetic resonance-thermal analysis may be a more responsive technique for studying thermoplastic behaviour, and can predict a number of other coal properties to a useful degree of accuracy. The feasibility of 15N CP-MAS NMR has been demonstrated by a study of nitrogen functionality in bituminous coals. MAS-NMR spectroscopy has been used to investigate the chemical environments of sodium, aluminium, silicon, phosphorus and boron in coal. The transformations of these elements in combustion processes have been elucidated by further MAS-NMR studies of ashes and boiler deposits. The results clearly demonstrate the potential of NMR spectroscopy for the in situ characterisation of coal minerals.

Additional information

Authors: BRITISH COAL CORPORATION, Coal Research Establishment, Cheltenham (GB)
Bibliographic Reference: EUR 14069 EN (1992) 81 pp., MF, ECU 4, blow-up copy ECU 13.50
Availability: (2)
Record Number: 199210558 / Last updated on: 1994-12-02
Original language: en
Available languages: en