Electron spin resonance of isolated coal macerals

• Published in: Fuel (Guildford) 1986-04, Vol.65 (4), p.558-565
• Main Authors: Silbernagel, Bernard G., Gebhard, Layce A., Dyrkacz, Gary R., Bloomquist, Carol A.A.
• Format: Article
• Language: English
• Subjects: Applied sciences; Coal and derived products; coal macerals; e.s.r; Energy; Exact sciences and technology; Fuels; Structure, chemical and physical properties
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/0016-2361(86)90049-9

The g-value, linewidth, lineshapes, carbon radical densities and microwave saturation response have been measured for over 50 exinite, vitrinite, and inertinite maceral samples of coals varying in rank from subbituminous type C to anthracite. The process of maceral isolation has also been examined by comparing carbon radical properties of the starting coal with those of intermediates in the separation procedure: after comminution, demineralization and centrifugation. The g-values, linewidths and lineshapes appear unaltered by the separation steps, while there is some decrease in carbon radical density upon comminution and an increase upon demineralization. Carbon radical g-values fall with increasing coal rank for both vitrinites and exinites, a change associated with loss of oxygen at higher rank. Linewidths generally increase with rank for both vitrinites and exinites, but are extremely narrow (≈1G) for some inertinites, suggesting exchange narrowing between radicals. Radical densities and the ability to absorb microwave radiation increase with coal rank for exinites and vitrinites, reflecting stronger inter-radical interactions at higher radical densities.