The application of 29Si and 27Al solid state n.m.r. spectroscopy to characterising minerals in coals

• Published in: Fuel (Guildford) Vol. 65; no. 3; pp. 437 - 441
• Main Authors: Barnes, Julian R., Clague, A.Derek H., Clayden, Nigel J., Dobson, Christopher M., Jones, Robert B.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.03.1986; Elsevier
• Subjects: 29Si and 27Al n.m.r. spectroscopy; Applied sciences; coal; Coal and derived products; Energy; Exact sciences and technology; Fuels; Structure, chemical and physical properties; coal; 29Si and 27Al n.m.r. spectroscopy; Characterization; Solid state; Petrographic composition; NMR spectrometry; Minerals; Coal
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/0016-2361(86)90311-X

Solid state 29Si and 27Al n.m.r. spectroscopy has been applied to mineral concentrates (termed low temperature ashes) from different coals to provide information on their mineralogy. In the 29Si n.m.r. spectra, two well resolved signals were observed in each case corresponding to silicate in quartz and in clays. The nuclear relaxation rates of the quartz components were found to be long and to vary between different samples. Measurement of the relative intensities of the two signals as a function of time allowed for nuclear relaxation, however, and permitted the values of the relative proportions of silicon as quartz and clay to be obtained in most cases. These agreed well with values obtained by X-ray diffraction (XRD) plus X-ray fluorescence (XRF). The 29Si n.m.r. data also provided some information on the nature of clays in coals. Combined with 27Al n.m.r. measurements, discrimination between kaolinite and illite clay components was possible by distinguishing aluminium in octahedral and tetrahedral coordination sites. Again, reasonable agreement with XRD and XRF was observed. The results show the potential and some limitations of solid state n.m.r. for such analytical application to coals.