Macerals electron spin resonance

Free Radicals in Macerals. Electron spin resonance (ESR) has been used to study carbon free radicals in coals, and to some extent, separated macerals. The technique provides information on radical density and the environment of the radicals. The resonance position, termed the g-value, is dependent on the structure of the molecule which contains the free electron. The line width is also sensitive to the environment of the unpaired electron. In an early study, Kroger (71) reported that the spin concentration varied between maceral groups with liptinite < vitrinite inertinite. For this limited set of samples the spin concentration increases with rank for liptinites and vitrinites and decreases for the micrinite samples. On the other hand, van Krevelen (72) found the same general results except... 

H. Tschamler. Dr. E. de Ruiter and I have also made electron spin resonance measurements on macerals (E. de Ruiter and H. Tschamler, Brennstoff-Chem. 42, 290 (1961)). We found quite similar results for micrinites to the single value reported by Given et al. 

This volume covers a wide range of fundamental topics in coal maceral science that varies from the biological origin of macerals to their chemical reactivity. Several chapters report novel applications of instrumental techniques for maceral characterization. These new approaches include solid l3C NMR, electron spin resonance, IR spectroscopy, fluorescence microscopy, and mass spectrometry. A recently developed method for maceral separation is also presented many of the new instrumental approaches have been applied to macerals separated by this new method. The contributions in this volume present a sampling of the new directions being taken in the study of coal macerals to further our knowledge of coal petrology and coal chemistry. 

Electron Spin Resonance of Isolated Coal Macerals... 

Electron spin resonance determinations of g-values, linewidths, radical densities and saturation properties have been performed on carbon radicals in samples of coal macerals isolated by density gradient centrifugation techniques. These data are compared with elemental analyses and density measurements. Each maceral type exhibits a different ESR signature" which can be understood in terms of the nature of the starting organic and the extent of coalification. 

There have been a large number of electron spin resonance (ESR) studies of coal and coal products,(1J but a microscopic interpretation of the resulting data has been hampered by the chemical heterogeneity of the coal samples examined. While several surveys of specially selected macerals have appeared, 3), the recent evolution of maceral separation techniques - now allows detailed ESR observations to be made on coals systematically fractionated in which coal rank, maceral type, and maceral density are simultaneously distinguished. The present report surveys the behavior of a variety of ESR properties of carbon radicals in exinite, vitrinite, and inertinite macerals in a variety of coals of different rank. These data... 

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See also in sourсe #XX -- [ ]

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