~(15)N NMR Spectroscopy of Coals and Pyrolysis Products

摘要

~(15)N NMR spectra are reported for a number of coals from Pacific Rim countries. Arguments are presented to explain discrepancies between observations and conclusions obtained from NMR experiments and those obtained by XPS and XANES techniques. Detection of different types of nitrogen species is discussed in terms of cross polarization dynamics together with the effects of the large chemical shift anisotropy that are found in different types of nitrogen functional groups. Significant differences are observed in the types of nitrogens present in these coals and these variations are associated with coal rank as has been in a previous study of the Argonne Premium coals. We have also begun to examine pyrolysis char and tar samples. The NMR data indicate that significant differences exist between the types of nitrogen structures observed in coal, char and tar samples. These differences suggest that different mechanisms may exist for nitrogen release from tar and char samples.